re procomm plus for windows problems kentiler matt ksu ksu edu kent p iler writes i have normal procomm plus for dos but i ve been considering buying the windows version it got really great reviews in computer shopper i have a friend who connects to the mainframe and unix machines here using it but the screen seems to have a problem keeping up with the modem he has a modem on a mhz machine i can t see it having trouble keeping up his pcplus for dos works great re what to do after the high speed modem arrives edition apr this article applies only to windows and and not to nt os or dos apps not running under windows one of the unadvertised limitations of most current windows pcs is that their rs c serial com performance is seriously deficient almost everyone who purchases a high speed modem v bis v pep or hst discovers the problem the first time they try to download a file or accept an incoming fax at after upgrading the modem overrun and retry errors abound even when the only active application is the datacomm or fax program if the transfer completes at all it may take even longer than with the old bps modem there are three reasons for the problem the universal asynchronous receiver transmitters uarts used in most pcs are primitive ns devices with single byte fifo buffers if the operating system driver cannot read and flush each character at high interrupt rates the next incoming character overwrites the fifo and the previous one is lost dos being a fairly single minded environment during datacomm can usually keep up windows can t windows has more operating system overhead than plain dos and interrupts often take longer to service overruns are much more likely than under dos as soon as you report to your pc modem vendor that you are losing data you may be advised that you need to upgrade to a more likely since there seems to be a conspiracy of ignorance about this issue you ll get no useful advice at all most of the store front and mail order sources i spoke with in attempting to solve my own problem had never heard the term and many didn t even know what a uart was even your pc has ns a uarts and ps s do or if you can upgrade your mother com board or add a new com board you may still experience errors and overruns because the standard microsoft windows com drivers don t take full advantage of the windows is improved in this regard over but i still recommend a driver upgrade applications like procomm win which is what i use cannot get around this problem by themselves if you have a modem card you may not have a problem as the modem part of the card can be designed to be aware of the state of the uart and avoid overrunning it however i wouldn t want to bet that the card designers were that clever and will insist on a uart if i ever buy a modem card some modem cards don t even have conventional uarts but if they are to work with standard windows drivers they need to simulate one use msd exe below to see what the modem card is or is pretending to be the hardware situation the uarts on most pc com ports are based on national semiconductor ns or ns chips or megacells inside vlsi chips where you can t replace them you can id the uart type on your system by running the microsoft diagnostic program windows msd exe be sure to run it in dos before bringing up windows the windows serial api may prevent msd from accurately identifying a if you run it from a windows dos prompt the ns uart has separate byte transmit and receive fifos with configurable trigger levels and can run reliably at clock rates up to bps although with current modem technology there s no point in pushing your luck by going over bps the has shorted access cycle times than the or the also has dma capability but it is not clear that any pc drivers ever use this for more technical info see national semiconductor application note an so what uart component do you have try to locate the uart on your mother board multi function i o card com board or isa mca modem card if you can t find a socketed component with the numbers or your com ports are probably buried in vlsi and you won t be able to perform a chip replacement if you can disable your vlsi com ports as i chose to do you can at least add an aftermarket com board if you have one or more socketed or chips you can buy plug in ns afn or pc c cn low power cmos version ics from several suppliers typically for to each the n chip is the normal pin dual in line package other styles are available but avoid any ns chips without the a the c c are presumably all ok early ns chips have bugs although national will reportedly exchange those of their own manufacture for free clone chips are available from various ic makers other than national the manual for the turbocom drivers states support for the following apparently equivalent chips national semiconductor a chips technology c texas instruments t c a silicon systems m vlsi c turbocom warns about the pre a ns and western digital c says that problems have been reported with early ibm ps sx and systems ibm reportedly will upgrade them if you don t have socketed chips you ll need to buy an after market com or multi function board if this is a modem card situation you may be hosed to add a new com or multi function card you ll need to either disable the com port s you are replacing or re assign them to com although watch out for irq conflicts without turbocom although cheaper cards are available in the interest of getting the problem solved quickly i elected buy the modular circuit technology mct aio card from jdr microdevices samaritan drive san jose ca voice us voice other fax us the mct aio and the is important sells for it is an bit isa card providing port type connector address and irq comments com db m com irq ns afn in socket com ribbon com irq ns afn in socket parallel db f lpt irq game ribbon the kit includes a ribbon cable and db f connector for the secondary com port a ribbon cable connector for the game port two bulkhead plates for the ribbon based connectors and a f to f adaptor cable each port can be individually disabled and the com ports have tx rx rts cts dtr dcd and dsr jumpers jdr also sells a super i o m f card that also has ide i have heard from several people about less expensive m f i o cards with s tsd systems for the card plus per greenfield trading and distributors voice fax their card is w one w and they sell afns for r s data systems inc east highway longwood fl phone fax com lpt game card w s for i have no personal experience with any of the firms except jdr meanwhile back at the mct card from jdr i only needed two serial ports and am running out of irqs on my pc so i disabled my built in vlsi based ports however with the turbocom driver below i could have set the internals as com and using irq sharing the software situation simply upgrading to uarts will not completely solve common overrun problems the standard ms serial drivers don t take full advantage of the the windows drivers are even less capable and the windows drivers have the following limitations they enable only the receive fifo and only at rates above bps they never enable the transmit fifo which results in an interrupt rate of x during uploads they set the trigger level at bytes too high it s easy for more bytes to arrive before the driver can read the fifo the ports menu of the control panel only allows speeds up to with a v bis modem sparse data and text can easily compress or more suggesting that a host dte connect rate of bps would be effective the api won t accept rates above cbr the api won t let dos programs know there is a there and even if it did dos programs that aren t aware get little benefit from a port with the standard drivers they don t allow irq sharing for com the bios doesn t initialize com properly in many systems windows provides no workaround for apps that don t provide port speed options above bps these problems are reportedly not solved in windows nt or dos and may or may not be addressed in any windows releases after but before rumors suggest they may be solved in windows you can get replacement drivers that solve all of those problems by buying a copy of turbocom current version from bio engineering research pacific commware division beacon hill lane ashland or voice fax bbs mcimail compuserve price was around as i recall bio eng is not set up to accept credit cards so i had to send a check egghead and software list turbocom but as far as i know they don t stock it bio is not a software company per se they apparently needed reliable hi speed serial connections for an in house instrument application wrote their own driver discovered a market for it revised it to be a general purpose com driver suite they recently upgraded it for windows it is run time licensed i now have my host dte connect rate set to bps most of my datacomm apps and i am having zero problems with downloads i routinely see transfer rates that exceed bps i am also using bps when linking an hp lx to my pc with lossless bi directional i o uploads to various remote systems are another matter because many hosts are still using antique uarts and drivers note that is still the highest rate that the windows port menu in control panel will allow in configuring a com port turbocom gets around this by allowing you to specify on each port a factor that will set the real uart rate to a multiple of the rate passed through the windows apis and dialog boxes i also have cts rts hardware flow control enabled and i suggest that you do the same even if you only ever transfer bit ascii data xon xoff is not a sufficiently reliable method of flow control the informal dec standard for xon xoff hysteresis is that the sender may transmit another yes sixteen bytes after receipt of the xoff from the receiving system or device the byte fifo in the is clearly not big enough to let us rely exclusively on xon xoff a well respected datacomm engineer has informed me that the s can t really do cts rts all by itself in the dos windows environment so using data rates above may still be risky even with hardware flow control a with turbocom can still experience overruns in very busy systems with lots of apps running and serious swapping in progress if this is your situation you may need to buy a co processed com board but this will cost you more than a turbocom upgrade a review of two such boards and a review of turbocom can be found in the feb issue of windows sources magazine i suggest trying a turbocom upgrade first and experiment with process priorities and time slices if you are a power user whose thrashing system still runs into comm problems closing soapbox comments the state of rs c serial datacomm support is an embarrassment across the computer industry because it is the oldest standard i o interface the job of designing hardware and writing software often seems to be assigned to the least senior or lowest ranked engineers at computer companies the design of the average serial port is at least ten years behind the state of the art in my last job with a major workstation vendor i lobbied for improved serial ports when they were doing the initial designs of a new system that family of machines was subsequently introduced with ports however this is the exception few computer companies seem to have any champions for decent i o you may as well learn what you can about serial i o because this situation shows no sign of improving soon when v fast arrives i expect cries of outrage from windows users world wide whose pcs sort of work today with v but will fail miserably with v fast without a hardware buffered uart like the and without software drivers that use that uart to best advantage a v fast modem will be a waste of money regards a east harmony road bob niland suite internet rjn csn org fort collins co compuserve copyright robert j niland all rights reserved permission is granted for automatic redistribution of this article via electronic magnetic and optical media in an unedited form through any usenet newsgroup where the article is posted by the author permission is granted for each compuserve and usenet reader subscriber and each person who received this article from compuserve an ftp site authorized by the author or via electronic mail from the author to retain one electronic copy and to make hardcopy reproductions of this edition of this article for personal non commercial use provided that no material changes are made to the article or this copyright statement all other copying storage reproduction or redistribution of this article in any form is prohibited without the express written consent of the author robert j niland eof
