re ide vs scsi wayne smith wlsmith valve heart rri uwo ca wrote in article qk kvinnndk dns nmsu edu bgrubb dante nmsu edu grubb writes point of view why does scsi have an advantage when it comes to multi tasking data is data and it could be anywhere on the drive can scsi find it faster can it get it off the drive and into the computer faster does it have a better cache system i thought scsi was good at managing a data bus when multiple devices are attached if we are only talking about a single drive explain why scsi is inherently faster at managing data from a hard drive ide integrated device electronics currently the most common standard and is mainly used for medium sized drives can have more than one hard drive asynchronous transfer mb s max why don t you start with the spec sheet of the isa bus first you can quote scsi specs till you re blue in the face but if they exceed the isa bus capability then what s the point who said isa was necessary eisa or vlb are the only interfaces worth investing thousands of dollars e g a new pc s worth of money in who says ide is limited to megs sec what about vlb ide does anyone know how they perform you didn t read to carefully vlb ide uses the same connection mechanism as standard ide if transfer rate is limited by ide whether it s interfaced to isa eisa or vlb matters not so at its lowest setting scsi interface in asynchronous scsi mode averages the through put maximum of ide in asynchronous mode in full scsi mode it blows poor ide out the window down the street and into the garbage can as implimented on what system on mine for one thing scsi blows ide out of the water hands down if ide has better throughput why isn t it used on workstations and file servers the problem becomes can the drive mechanisim keep up with those through put rates and that is where the bottleneck and cost of scsi comes from not the interface itself but more and more from drive mechanisims to use the scsi through put given the original question scsi used only as a single hard drive controller is it then necessary to get a scsi drive that will do at least maybe megs sec for the scsi choice to make any sence what does a meg megs sec scsi drive cost no that s the nice thing on a multitasking os scsi can use both drives at once i ve got unix loaded on one of my pcs along with windogs and the os can only use one of the two ide drives at one time it s pretty ugly i just bought at quantum for my mac at home i paid for it i haven t seen ide drives cheaper the original cga cart back in was i think the original ega card or pga was scsi has stood relatively alone in not coming down in price mainly because we re talking about pc s and not sun s or sparc or sgi or name your favorite unix workstation that is after millions of pc buying decisions over the years scsi has had plenty of time to come down in price no actually we re talking about scsi being expensive simply because nobody did a common interface for the pc if they had a common read easily implemented method of adding scsi to a pc like as in a sun or mac then you d find scsi the connection medium of choice i won t argue that the scsi standard makes for a good well implimented data highway but i still want to know why it intrinsically better than ide on an isa bus when it comes to multi tasking os s when managing data from a single scsi hard drive on a single drive scsi is more expensive but you bought your pc for expandibility so you d want to add more drives or whatever the following are why i find scsi intrinsically better than ide a partial list you can add many different types of devices and access them concurrently a scsi device works on many different machines i have a mac and a pc at home and moving hard drives between them is very nice with scsi hook them up and away they go scsi devices work together better than ide devices for instance recently i added an older connor meg ide to a maxtor meg ide the connor must be setup as the slave it will work no other way on scsi you set the address check the termination plug it in and away it goes i have a problem with ide s mutual exclusion i notice that the time it takes to switch from accessing drive c to drive d is quite long as compared to the time it takes to switch from drive c to d on a scsi system under a multitasking os this is very noticable as many things can be going on at once one neat thing that i ve noticed lately a fringe benefit has been the ability to add older almost dead drives as storage on a scsi system with little problem we ve got a bunch of almost dead meg drives that i ve added to my pc i ve now got the interface full but it does allow me to have meg drives meg drive tape drive and meg drive all on the same card simply put scsi is handier than ide no mysterious jumpers to figure out greg you can t go against nature because when you do greg shaw go against nature it s part of nature too shaw feanor xel com love rockets uunet csn xel com shaw
