Tandy 1000
The Tandy 1000 is the first in a line of IBM PC compatible home computer systems produced by the Tandy Corporation for sale in its Radio Shack and Radio Shack Computer Center chains of stores.

Overview
In December 1983, an executive with Tandy Corporation, maker of TRS-80 computers, said about the new IBM PCjr: "I'm sure a lot of people will be coming out with PCjr look-alikes. The market is big". While preparing the Tandy 2000—the company's first MS-DOS computer—for release in November 1983, Tandy began designing the Tandy 1000, code named "August". Unlike the 2000 it would be PC compatible with the IBM PC, and support the PCjr graphics standard.

Released in November 1984, the $1,200 Tandy 1000 offered the same functionality as the PCjr, but with an improved keyboard and better expandability and compatibility. "How could IBM have made that mistake with the PCjr?" an amazed Tandy executive said regarding its chiclet keyboard, and another claimed that the 1000 "is what the PCjr should have been".

The Tandy 2000—not completely PC compatible—quickly failed. Although the press saw the 1000 as former personal-computer leader Tandy admitting that it could no longer focus on proprietary products in a market the IBM PC dominated, the 1000 sold more units in the first month than any other Tandy product and by early 1985 was its best-selling computer. The 1000 has joystick ports like the PCjr, and its 16-color graphics and 3-voice sound, but not the PCjr ROM cartridge ports. Since IBM discontinued the PCjr soon after the release of the 1000, Tandy quickly removed mentions of the PCjr in its advertising while emphasizing its product's PC compatibility.

Although Tandy initially marketed the 1000 as a business computer like the IBM PC, InfoWorld stated in 1985 that the company "produced a real home computer". The company claimed that the 1000 was "the first fully IBM PC-compatible computer available for less than $1000". The 1000 helped the company obtain a 9.5% share of the US home-computer market in 1986, a year in which Tandy stated that half of its compatibles were purchased for the home. In 1988 CEO John Roach disagreed with Apple counterpart John Sculley's rejection of the home market: "Let him deny it. He's the only other person that's well-represented in the home market, and if he wants to abandon it, it's all right with me". Tandy also regained a significant share of the Apple-dominated educational market, which the two companies had once equally shared.

The 1000 and its many successors were successful, unlike the PCjr, partly because it was sold in ubiquitous Radio Shack stores and partly because the computer was less costly, easier to expand, and almost entirely compatible with the IBM PC. The PCjr's enhanced graphics and sound standards became known as "Tandy-compatible". With its graphics, sound, and built-in joystick ports, the 1000 was the best computer for PC games until VGA graphics became popular in the 1990s. Software companies of the era advertised their support for the Tandy platform; 28 of 66 games that Computer Gaming World tested in 1989 supported Tandy graphics.

Design and architecture
Tandy 1000 computers were some of the first IBM PC clones to incorporate a complete set of basic peripherals on the motherboard using proprietary ASICs, the forerunner of the chipset. Although the original Tandy 1000 came in an IBM PC-like desktop case, some models, notably the 1000 EX and 1000 HX, used home-computer-style cases with the keyboard, motherboard and disk drives in one enclosure. This high level of integration made these machines a cost-effective alternative to larger and more complex IBM PC/XT and PC/AT-type systems, which required multiple add-in cards, often purchased separately, to implement a comparable feature-set to the Tandy 1000.

Being derived from IBM's PCjr architecture, the Tandy 1000 offered several important features that most IBM PC-compatibles of the time lacked, such as the PCjr's sound generator and extended CGA-compatible graphics controller. It also offered multiple built-in I/O ports, including a joystick port which was frequently a separate add-on card on non-Tandy machines.

The original line was equipped with the Intel 8088 CPU, which was later extended to faster clock speeds and also the 8086, 80286 and toward the end of the line with the RSX, 80386SX processors. Successors to the 1000 appended two or three letters to the name, after a space (e.g. Tandy 1000 EX and Tandy 1000 HX).  In a few instances, after these letters a slash was appended, followed by either a number or additional letters (e.g. Tandy 1000 TL/2, Tandy 1000 RL/HD).

Retirement
By 1993, changes in the market made it increasingly difficult for Tandy Corporation to make a profit on its computer line. Tandy Corporation sold its computer manufacturing business to AST Computers, and all Tandy computer lines were terminated. Radio Shack stores then began selling computers made by other manufacturers, such as IBM and Compaq.

Reception
In an article subtitled "Junior meets his match", John J. Anderson of Creative Computing called the original Tandy 1000 "the machine IBM was too inept, incapable, or afraid to manufacture. It is sure to put a whopping dent not only into PCjr sales, but into sales of the PC 'senior' as well". He favorably mentioned its low price, good PC-software compatibility, and bundled DeskMate ("you might never need another software package for your computer"). 80 Micro approved of the 1000s PC compatibility and stated that the exterior design "gives it a feeling of quality and confidence". The magazine concluded that "Tandy's machine closely emulates the most basic functions of an IBM PC, and it does so at an affordable price ... along with the security of Tandy's substantial support network", but wondered if people would buy the 1000 if IBM lowered the price of the PC.

InfoWorld noted the 1000s low price ("fully one-third less than a comparably equipped IBM PC"), predicted that the computer was really intended for "the elusive home computer market", and speculated that "in retrospect it might have been the PCjr's final straw". The magazine called the 1000 "almost as fully IBM PC compatible as a computer can get", but gave DeskMate a mixed review and advised customers of the computer's inability to use full-length PC expansion cards. It concluded that "By making the 1000 inexpensive and adaptable" and including DeskMate, "Tandy produced a real home computer".

BYTE called the 1000 "a good, reasonably priced IBM PC clone that has most of the best features of the IBM PC and PCjr ... at current prices it is a very good alternative". It noted the high level of software compatibility and the good keyboard, and stated that DeskMate was "fairly good ... but a little extra programming work could have turned [it] into a much better program", noting that—for example—the word processor did not have a Move command. The magazine also mentioned the computer's short slots. PC Magazine also noted the slots and criticized the Tandy 1000's fit and finish, but acknowledged the computer's low price and bundled hardware features.

Technical details
All Tandy 1000 computers featured built-in video hardware, enhanced sound hardware (based on one of several variants of the Texas Instruments SN76496 sound generator) and numerous peripheral interfaces, including game ports compatible with those on the TRS-80 Color Computer, an IBM-standard floppy-disk controller supporting two drives, and a parallel printer port, all integrated into the motherboard in addition to the hardware standard on the IBM PC/XT and, in later Tandy 1000 models, PC/AT motherboards.

For the original Tandy 1000, the designers omitted a direct memory access (DMA) controller because the PCjr does not have one, and they believed that those who needed it would add it with additional memory for the computer; they omitted the RS-232 port because all Tandy printers use the parallel port and, they believed, most customers would use internal modems. The earlier models of the Tandy 1000 had a composite video output, and could be used with a color or monochrome composite monitor, or a TV with an RF modulator. The original 1000 and SX had a light-pen port. Unlike most PC clones, several Tandy 1000 computers had MS-DOS built into ROM and could boot in a few seconds. Tandy bundled DeskMate, a graphical suite of consumer-oriented applications, with various Tandy 1000 models. 
 
Early Tandy 1000 models used Phoenix BIOS. Common models of the machine included the Tandy 1000, 1000 EX, 1000 HX, 1000 SX, 1000 TX, 1000 SL, 1000 RL, and 1000 TL. With the exception of the RLX and RSX, the Tandy 1000 machines are XT-class machines, which cannot support extended memory despite some models using 80286 processors. The RLX is an oddity, as it is an XT-class machine that supports 384 KB of extended memory, and the RSX is a fully AT-class machine which can support up to 9 MB of extended memory.

Expansion slots 
With the exception of the 1000 EX and HX, Tandy used industry standard 8-bit XT ISA slots in their desktop models, including the SX, TX, SL, and TL series, but the actual length was limited to 10.5 inches or shorter, rather than the industry standard XT length of 13 inches. While many 8-bit cards met this length requirement, some cards such as hard cards, EMS memory cards, and multifunction cards that required the standard 13" length did not fit in the 1000's case. The EX and HX utilized a PLUS-style connector, which was electronically identical to an 8-bit XT ISA slot, but had a 62-pin Berg connector instead of a card edge, rendering it incompatible with ISA cards without an adapter. The PLUS connector was designed for compactness in these models with built-in keyboards. The 1000 RSX featured two 16-bit AT ISA slots.

Hard disk drives
As hard disk drives at the time of the Tandy 1000's introduction were very expensive, Tandy 1000 systems were not usually equipped with hard drives. However, it was possible to add a hard drive to most Tandy 1000 computers. Most of the desktop-type Tandy 1000 units could accept regular 8-bit ISA bus MFM, RLL and SCSI controllers like typical XT-class machines; however, care had to be taken when configuring the cards so that they did not cause conflicts with the on-board Tandy-designed peripherals.

For most Tandy 1000 models (other than the compact EX and HX) that did not come already equipped with a hard drive, Tandy offered hard disk options in the form of hardcards that were installed in one of the computer's expansion slots and consisted of a controller and drive (typically a 3.5-inch MFM or RLL unit with a Western Digital controller) mounted together on a metal bracket. Their own 20 MB hard card was offered for $799, though compatible third-party units were available. Although this arrangement provided a neat physical coupling between the controller and the disk, single-sector internal transfers and dependence on the speed of the host machine to transfer data to memory meant that a trial-and-error approach was still needed to set the disk interleave correctly to ensure optimum transfer rates. Furthermore, as the Tandy 1000's slots were only 10.5" long and are 8-bit only, some units would not fit and/or operate correctly unless they were certified to be Tandy-compatible.

Starting with the Tandy 1000 TL/2, XT IDE controllers were integrated onto the motherboard. However, these were incompatible with common AT IDE hard drives. The TL/2, TL/3, RL and RLX all used the XT IDE interface, where the later (and significantly upgraded) RSX was the only Tandy 1000 model computer to use a standard AT IDE interface. One option for modern users of these systems is to install and use XT ISA CompactFlash adapter; this is also the most practical way to install a hard drive into a Tandy 1000 EX or HX, using an adapter cable that adapts the male PLUS-style connector to an 8-bit ISA card-edge slot.

I/O and ports 
Tandy 1000, SX, TX used a proprietary 8-pin round DIN connector for the keyboard port that was compatible with the older TRS computers but not compatible with the IBM PC/AT or PS/2 standard. Some scan codes differed between the Tandy 1000 and IBM PC/XT and AT, resulting in software compatibility issues. The SL/TL and later used a more directly PC/XT-compatible keyboard protocol, and the 1000 RSX used a PC/AT and PS/2-compatible protocol.

Tandy 1000 used a proprietary 6-pin female round connector for the joystick port that on the SX/TX was adjacent to the keyboard port in the front of the computer. As with the keyboard, it was compatible with the older TRS-80 and Tandy color computer models, but not compatible with the IBM standard 15-pin male game port. Some DOS games do not work with these joystick ports, but those that support Tandy 1000 graphics and sound work.

Early Tandy 1000 models used a non-standard card-edge parallel printer port rather than industry standard DB-25 printer port. It required a Tandy-1000 compatible printer cable to connect to a standard printer parallel port. This was later changed to a standard DB-25 connector on the 1000 RL.

Tandy 1000TX and beyond used a proprietary floppy drive cable port, that also powered the floppy drive. It required a Tandy 1000 compatible floppy drive, though it may be possible to modify a floppy drive cable to make a standard floppy drive work.

Operating systems and environments 
Tandy shipped PCs with their own customized version of MS-DOS, which are compatible with Tandy graphics and keyboard. The most current version of MS-DOS for Tandy 1000 is DOS 3.22. Tandy 1000s came shipped with one of several varieties of Deskmate, their own GUI productivity software suite.

There may be compatibility issues with later versions of DOS such as DOS 5 and DOS 6. Until the 1000 RLX, Tandy 1000s were typically limited to 640 KB main memory, and non-Tandy versions of DOS often reduce the memory available for applications and games. In addition, the hardware detection routine for the installer of Microsoft MS-DOS 6 could corrupt the serial EEPROM of Tandy 1000 HX machines.

Tandy 1000s could work with Windows 1.0, 2.0 and 3.0 but not 3.1, with the exception of the RLX which could run Windows 3.1 in Standard mode, and the RSX which fully supported running Windows 3.1 in 386 Enhanced mode.

Peripherals

Monitors 
Tandy offered two color monitors specific for its Tandy 1000 computers: the CM-5, with a 0.64 millimeter dot pitch, and the Tandy CM-11 with a dot pitch of 0.42 mm. Both were 13-inch displays and had a power cable and a nine-pin RGB cable to attach to the Tandy CGA port. The more expensive CM-11 also supported a special proprietary Tandy enhanced 225 scan line text display mode.

Tandy also offered monochrome monitors that support MDA and Hercules standard that also work with Tandy 1000. As it uses a CGA-compatible interface, non-Tandy monitors that support CGA should work.

Keyboard 
The original Tandy 1000, SX, EX, TX, HX used a proprietary keyboard and keyboard layout that was not compatible with the PC/XT/AT standard then in use. The layout of the keyboard prefigured the IBM Model M keyboard, with function keys arranged in a row at the top, instead of on the left as in the PC and PC XT/AT. Later models of the Tandy 1000 series, such as the 1000 SL, TL and RL series used a keyboard more similar and compatible with the IBM PS/2 series keyboard connector and layout.

Mouse options 
As the Tandy 1000 used the same game ports as the Tandy Color Computer series, the 26-3025 Color Mouse and 26-3125 Deluxe Mouse were compatible with the Tandy 1000, though not all DOS software and drivers were written to recognize them. The Tandy Digi-Mouse was also available, which required a separate controller that was available in either ISA or PLUS format. Systems with RS-232C serial ports could use standard serial mice, and later systems, such as the 1000 RL, featured a PS/2 mouse connector.

Joystick options 

Radio Shack offered one button joystick that worked with its proprietary  6-pin DIN joystick connector that was compatible with the older TRS-80 Color Computer but not standard 15-pin IBM PC game ports often found on sound cards and i/o multifunction ISA cards. It worked with many games written to take advantage of Tandy graphics and sound.

Modem options 

Radio Shack offered Tandy 1000 PLUS 300-Baud PC Modem that was compatible with the 1000EX/HX that used PLUS slots. Radio Shack also offered 2400-baud internal modem. Third party modems with speeds of 14k baud should work provided they are eight-bit ISA, and fit.

Printers 
Radio Shack sold the Tandy DMP-130A dot matrix printers to go along with their Tandy 1000 line, along with compatible card-edged printer cable. This printer was sold at home budget prices. Radio Shack often offered a package bundle with a Tandy 1000 computer, CM-5 budget monitor and DMP-130A printer. Using specially-designed aftermarket cables, it was possible to connect non-Tandy printers to the system.

Apple IIe compatibility 
 
Tandy Radio Shack wanted to compete in the education, school and home markets, which were dominated at the time by the Apple IIe.  In 1987, they partnered with Diamond and through Radio Shack sold the Diamond Trackstar 128 series Apple IIe compatibility board for $399, and offered free installation in their Tandy 1000 series. This peripheral was similar to Apple IIe Card sold later for certain Macintosh models; it was a fully functional Apple IIe clone with 128KB RAM and 6502 CPU and double high-resolution graphics which, allowed Tandy 1000 computers to run software written for the Apple IIe and IIc platform, an especially important consideration in the education market of the time. It was also marketed to home users and businesses interested in having both MS-DOS and Apple II compatibility.

The board has a pass-through RGB cable and floppy drive cable, and required an open 10-inch 8-bit ISA slot, and used a boot disk to boot into Apple mode. The boot disk has both DOS and Apple software and is copy-protected. Compatibility was fairly good and allowed Tandy 1000 owners to run most Apple II software on their Tandy 1000 machine for less than the cost of owning  separate IBM PC and Apple II systems.

Many Tandy 1000s sold to schools came with the Diamond Trackstar 128 installed, and    home owners also purchased this for compatibility with both DOS and Apple II software.

System specifications

Full-size desktop systems

Compact and all-in-one systems

Selected models

Tandy 1000
The original Tandy 1000 was a large computer almost the size of the , though with a plastic case over an aluminium lower chassis to reduce weight. 
It came standard with one internal 5.25" double-density floppy disk drive, with an additional exposed internal bay usable for the installation of a second 5.25" disk drive (available as a kit from Radio Shack). The floppy drives used jumpers to select the drive number instead of the IBM cable twist. The standard memory was , with the computer accepting up to  of total memory with the addition of expansion cards.

MS-DOS 2.11, DeskMate 1.0, and a keyboard with the same layout as the Tandy 2000's were included with the computer. Like the PCjr, the Tandy 1000 motherboard did not supply DMA, but unlike that system, it could have DMA added with a memory expansion board.  While the Tandy 1000 had three XT-compatible expansion slots, early Tandy memory upgrade boards took up two of the slots to get to . Because the slots were  inches in length instead of the PC's 13 inches, full-length cards did not fit, but reviewers noted that the many built-in hardware features reduced the need for cards.

A later revision of the original Tandy 1000 model was the Tandy 1000A. This revision fixed bugs, scanned expansion cards for bootable ROMs, and added a socket for an Intel 8087 math coprocessor.

Tandy 1000 HD
The original Tandy 1000 (and many other models), like most home computers sold at the time, did not have a hard disk drive.  The Tandy 1000 HD was essentially an original Tandy 1000 with a hard disk option factory installed.  The factory hard disk had a capacity on the order of 10 or 20 MB.

Tandy 1000 SX and TX

The Tandy 1000 SX and TX were upgraded versions of the original Tandy 1000, utilizing a similar chassis. Two major upgrades over the original Tandy 1000 were the inclusion of a DMA controller, which improved the speed of diskette operations and IBM PC-compatibility of these systems, and the addition of two additional ISA expansion slots, to offer a total of five 8-bit ISA slots.

1000 SX
The Tandy 1000 SX used a 7.16 MHz 8088-2 processor, had 384k of memory (upgradeable to 640 KB on the motherboard), came with either one or two 5.25" internal floppy disk drives, and had the light pen port (not a serial port) like the original Tandy 1000. An adjustable potentiometer inside the system controlled the volume of the internal speaker. The Tandy AX was an SX rebadged for sale in Walmart stores. The 1000 SX came with MS-DOS 3.2 and Deskmate II on 5.25" 360kB diskettes.

The SX was the first Tandy 1000 in which the built-in video circuitry could be disabled via DIP switch. This was to permit the installation of an upgraded graphics card, typically an EGA or VGA card, in an expansion slot.

1000 TX
The Tandy 1000 TX was similar to the 1000 SX with its detached keyboard, unique parallel port edge connector and XT-style architecture in a slightly modified case. The major difference was the 80286 CPU clocked at 8 MHz. Similar to the IBM XT 286, it featured a 16-bit-wide memory bus, although the on-board peripherals and ISA slots were 8 bits wide.

The TX had a 3.5" internal floppy disk drive mounted in a 5.25" bay with room for an optional second internal 3.5" or 5.25" floppy disk drive. The rear panel had the same ports as the 1000 SX, except that an RS-232C serial port replaced the light-pen port. The memory size was 640 KB, with sockets for an additional 128 KB devoted to the onboard video logic. This extra 128 KB could only be used for and by the on-board video controller, so it was impractical to expand the on-board memory beyond 640 KB if a VGA graphics card was installed. The computer came bundled with Personal DeskMate 2.

The TX was the last 1000-series computer to use DIP switches to store the system configuration parameters.  All newer 1000s rely on CMOS static RAM chips powered by a battery soldered to the circuit board. These batteries degrade with time (as well as often leaking acid which ruins the circuit board) and must be replaced to restore full functionality after any lengthy period of disuse.

Tandy 1000 EX and HX
The Tandy 1000 EX and HX were designed as entry-level IBM-compatible personal computers, and marketed as starter systems for people new to computing. They were offered in a compact, all-in-one chassis that featured a 7.16 MHz 8088 (capable of clocking down to 4.77 MHz), 256 KB of memory (expandable to 640 KB with a PLUS memory expansion board), PCjr- and CGA-compatible Tandy Video graphics controller, a keyboard and, depending on the model, either a single 5.25" 360 KB floppy drive, or one to two 3.5" 720 KB floppy drives. An external floppy drive could be connected to a port on the back. The machine itself supplied power to the external drive, so only Tandy's floppy drive unit was usable with the EX and HX. The external drive was the standard 360 KB 5.25 inch format; in 1988 a compatible 720 KB 3.5 inch model was offered.

The EX and HX are upgradable via Tandy PLUS cards, and these systems have bays for three cards. A PLUS card connector is electrically identical to an ISA slot connector, but uses a Berg-style 62-pin connector instead of a 62-contact ISA card-edge connector. Other PLUS cards could be installed to add serial ports, a 1200-baud modem, a clock/calendar and bus mouse board, or a proprietary Tandy network interface. Radio Shack later sold an adapter card allowing installation of a PLUS card into a standard ISA slot, such as those in the larger Tandy 1000 models.

Like the original Tandy 1000, the EX and HX do not have a built-in DMA controller, though one can be added using the PLUS memory expansion board.

1000 EX

The Tandy 1000 EX featured a 5.25" floppy drive built into the right-hand side of computer casing. The EX sold for US$1,000 from Radio Shack in December 1986. The EX and, later, the HX would be among the most popular of the Tandy 1000 line because of their (relatively) low price.

A useful feature for the EX and later systems was the ability to boot off either drive, as the drives could be logically swapped when the system booted, so that the drive that was normally drive B: became drive A:, and vice versa, and the drives remained swapped until the system was powered off or reset.  (The SX and TX have this capability as well.)

The 1000 EX came with MS-DOS 2.11 and Personal Deskmate on 5.25" 360kB diskettes. The MS-DOS was a version specialized for and only bootable on the Tandy 1000; it included a version of BASICA (Microsoft's Advanced GW-BASIC) with support for the enhanced CGA graphics modes (a.k.a. Tandy Graphics or TGA) and three-voice sound hardware of the Tandy 1000.

1000 HX

The Tandy 1000 HX was an updated version of the EX. It utilized the same architecture and PLUS cards as the EX; however, one obvious difference was that it offered two 3.5" bays on the front panel, occupied by one or two 720 KB 3.5" floppy drives, as opposed to a single side-mounted 5.25" bay and floppy drive with the EX. It also had Tandy MS-DOS 2.11R in ROM, which could be accessed by starting the computer with no bootable disk present. Another improvement over the EX is the addition of a serial EEPROM to store configuration information, enabling similar functionality to today's CMOS NVRAMs. By comparison, earlier Tandy 1000 models, like IBM PC and PC/XT systems, used DIP switches and jumpers for startup configuration settings.

By putting the basic elements of DOS and Deskmate in ROM and eliminating the memory test on startup, the HX booted quickly compared to other contemporary MS-DOS machines, despite having no immediate provisions for a hard disk drive.

In addition to Tandy MS-DOS 2.11R, the HX shipped with Personal Deskmate 2. Most versions of MS-DOS worked with the 1000 HX, including DOS 3.x and some later versions. There was, however, a quirk in the DOS 4.0 environment that prevented that version of DOS from working with Tandy 1000 HX computers. Additionally, the installer for MS-DOS 6 could corrupt the contents of the serial EEPROM.

Tandy 1000 SL and TL series
The Tandy SL and TL series of computers were updates of the SX and TX, respectively. In addition to offering redesigned cases, the machines offered a more integrated motherboard with improved graphics and sound capabilities while dropping composite video output. The graphics controller now supported  resolution as well as a Hercules Graphics Card-compatible,  mode for monochrome monitors. Sound capabilities now included an 8-bit monaural DAC/ADC, which was similar in function to parallel port sound devices (such as the Covox Speech Thing and Disney Sound Source) but was extended to support DMA transfers, microphone input capability, and sampling rates up to 48 kHz. The SL/TL lines allowed the on-board floppy controller, parallel port and serial ports to be disabled, which the earlier models did not.

The SL and TL were also shipped with MS-DOS 3.3 and DeskMate 3 in ROM, and featured a serial EEPROM memory chip to store BIOS settings. The machines could also run 'normal' MS-DOS 3.x, 5.x, and 6.x and Windows 2.x and 3.0 operating systems, although Windows was limited to real-mode operations. In common with many PC clones of the era, MS-DOS 4 was problematic and generally avoided.

1000 SL and SL/2

The Tandy 1000 SL and SL/2 feature an Intel 8086 processor running at 8 MHz. This is socketed, and thus upgradeable with an NEC V30. The SL came with  of RAM preinstalled, whereas the SL/2 offered . Both machines could be expanded to , although the graphics controller reserved a portion of this memory, yielding only  available the operating system, even on systems using add-in ISA graphic cards. The SL line had the mic/earphone ports, volume knob and reset button on a small satellite board. A jumper on the board allowed the user to change the microphone input to a line-level output. The SL series offered five 8-bit XT-compatible ISA slots, and did not come with pre-installed real-time clock chips, making them optional upgrades in the form of the plug-in Dallas DS1216E SmartWatch.

The SL is the only machine in the line that offers an upper 5.25" bay, and therefore the only model to offer two 5.25" bays, where the other models, including the SL/2 and the entire TL range, feature two upper 3.5" bays and one lower 5.25" bay. As a result, fitting a hard drive to an SL that already has the upper and lower 5.25" bays populated may require either the removal of one of the devices in those bays, or the installation of a hard disk card-style bracket which seats in one of the ISA slots.

1000 TL, TL/2 and TL/3
The Tandy 1000 TL and TL/2 used 8 MHz Intel 80286 processors, whereas the TL/3 used a 10 MHz 80286. The TLs had 640 KB of memory preinstalled, with an option for an extra 128 KB for video frame buffering just as in the 1000 TX. Unlike the SL series machines, the TL machines came with the SmartWatch real-time clock logic built-in, which was powered by a removable 3-volt CR2032 button-cell battery on the motherboard.

The TL offered five 8-bit XT-compatible ISA slots, while the TL/2 and TL/3 offered four slots and an on-board 8-bit, XT IDE-compatible hard disk interface, which was not compatible with standard AT IDE hard drives. The TL series offered two upper 3.5" bays and one lower 5.25" bay. The TL/3 also offered a high-density floppy drive controller for 1.44 MB drives, though it shipped with a double-density 3.5" 720 KB drive.

As the processors on the TL-series are socketed, it is possible to install 386SX or Cyrix 486SLC-based processor upgrades, though the benefit of installing more advanced processors is limited beyond merely providing a speed increase due to the computers' XT-based architecture, and their resulting inability to access extended memory above 1 MB.

Tandy 1000 RL-series and RSX

The Tandy 1000 RL/RLX/RSX series were slim-line desktop home computers. They featured a much more compact case, with at least 512 KB of memory pre-installed, smaller PS/2-style keyboard and mouse ports, and at least one ISA expansion slot. The RL-series and RSX include provisions for an internal hard disk drive, depending on the model: the RL-series featured a built-in XT-IDE hard drive interface, while the RSX featured an AT-compatible IDE interface. The keyboard connectors of the RL-series, while similar to and mechanically compatible with PS/2-style connectors, were not fully compatible with typical PS/2 keyboards, as the keyboard uses the XT keyboard protocol. The RSX, however, incorporated the AT keyboard protocol, making it the first 1000-series system to offer more complete compatibility with typical PS/2 keyboards, and AT keyboards using an adapter.

1000 RL and RL/HD
The RL and RL/HD featured a surface-mounted  8086 processor, 512 KB of RAM (expandable to 768 KB to provide 128 KB for video and 640 KB conventional memory), a DB-25 unidirectional parallel port instead of the edge-connector ports, and the SL's enhanced graphics and sound. A single half-size 8-bit expansion slot was available. The RL/HD had a battery-backed real-time clock chip to store date and time information, which the RL lacked. These models also had MS-DOS and a portion of DeskMate in ROM, and could therefore boot much faster than many other computers on the market. The RL/HD came with a 20MB drive preinstalled.

1000 RLX
The RLX was the 'mid-range' offering of the RL line. It had a 10 MHz 286 (surface-mounted) and 512 KB of RAM, and unlike other 286-based Tandy 1000 models, it supported 384 KB of extended memory when RAM was expanded to the maximum 1 MB. However, it was not a full AT-class machine, as it still had an 8-bit ISA bus (as with the RL, one half-size expansion slot) and only 8 IRQs and 4 DMA channels. While the three-voice sound chip and DAC were still present, Tandy video was dropped in favor of an AcuMos VGA controller offering 256 kB of video memory and standard VGA graphics resolutions. The parallel port was bidirectional, a first for the Tandy 1000 series. The RLX had one 1.44 MB 3.5" floppy drive; an empty drive bay could host a second such drive. The hard disk RLX/HD came with a 20 MB hard disk and 1 MB RAM preinstalled. The hard disk occupied the empty drive bay, so this version supported only a single floppy drive.

1000 RSX
A more upscale offering, the RSX offered a 25 MHz 80386SX processor, 1 MB RAM, two 16-bit ISA slots, AcuMos SVGA video, a bidirectional parallel port, and standard PS/2 keyboard and mouse ports. It was a full 386-class PC and could run Microsoft Windows 3.x. Two sockets for SIMM memory cards were provided. Only 1 MB or 4 MB SIMMs of the 9-chip type were supported, and if two were installed they had to be of like capacity. With two 4 MB SIMMs installed, the 1000 RSX could be expanded to 9 MB RAM (without using an ISA slot). The RSX/HD variant came with a 52 MB hard drive using an AT-compatible IDE interface; replacement hard drives up to 504 MB could be substituted. Because of the slimline case, only one hard drive could be installed alongside the 1.44 MB 3.5" floppy drive.

The motherboard had a socket for the 80387SX math coprocessor. The RSX still retained the Tandy 1000 3-voice sound hardware and DAC, though the I/O address for the 3-voice sound chip was moved, rendering many games previously compatible with it unable to play music unless modified. The DAC could be used to emulate the Covox Speech Thing via MS-DOS device drivers for limited sound support. This worked with the game Chuck Yeager's Air Combat.

Windows 3.xx sound device drivers were available that worked in Windows 95 (with full 9MB RAM) on Tandy 1000 RSX.
The ACUMOS VGA graphics could be software-updated with Cirrus Logic BIOS (via MS-DOS driver) to allow VESA/SVGA to function in Windows 95, as the Windows 3.xx Tandy VGA drivers were insufficient for Windows 95.

Selected Tandy 1000-enhanced software

Major software publishers and makers of game and educational software, such as Sierra and Broderbund, offered software titles that specifically supported Tandy's unique and proprietary 16-color graphics, 3-voice sound, and other Tandy specific hardware features. These enhancements offer a superior graphics and sound experience for Tandy 1000 owners over standard DOS titles. Software that supported Tandy's graphics were typically labelled on the package as Tandy 1000/PCjr compatible. Many Tandy 1000 enhanced games are featured on YouTube.

Although the Tandy 1000 can run most DOS software, the below programs are known to specifically support Tandy 1000 enhanced features. These programs require DOS to run. Tandy shipped its own version of DOS. Tandy used the main memory for graphics, as a result most programs require 640k or 768k to run. The enhanced graphics and sound often tax the processor, so an 80286 processor or faster is recommended for best results.

There are also games and educational software that supports second generation Tandy 1000 graphics and sound, which offers 640 by 200 by 16 colors, and 8-bit DACs, found only on the 1000 sl/tl series. Examples of such software includes Mario's Typing Tutor, Star Trek, Freddy Pharkas: Frontier Pharmacist, Sargon Chess.

References

External links
 Radio Shack Tandy Computer Support, the official support site for Tandy Computers (product search page)
 The Tand-Em Project, a Tandy 1000 emulator project
 DOSBox MS-DOS, Tandy 1000, PCjr Emulator
 MESS Multiple emulator with Tandy 1000HX support
 Tvdog's Archive, Major archive of Tandy 1000 programs and documentation
 Tandy 1000 BASIC Programs, Games and applications
 The OldSkool Shrine, Tandy 1000 History And Memories
 Tandy 1000 Webring, More Sites On The Tandy 1000
 Low End Mac's retrospective on the Tandy 2000 computer and Tandy 1000 series (Daniel Knight - 2015-12-19)
 
  80 Micro preview article on the Tandy 1000, December 1984
  80 Micro review of the Tandy 1000, April 1985
  80 Micro review of the Tandy 1000 SX, August 1987
  80 Micro review of the Tandy 1000 TX, March 1988
  80 Micro review of the Tandy 1000 EX, May 1987
  80 Micro review of original Deskmate for Tandy 1000

Home computers
RadioShack
IBM PC compatibles
Computer-related introductions in 1984
Products introduced in 1984