wargopl@image.soe.clarkson.edu (Peter L. Wargo) (05/25/90)
From article <451@isgtec.UUCP>, by bmw@isgtec.UUCP (Bruce Walker): > In article <1990May23.154706.16476@sq.sq.com> ian@sq.sq.com (Ian F. Darwin) writes: >> In fact, dozens or hundreds of people used SC-DOS before IBM bought it from >> Microsoft who in turn bought it from a small company named Seattle >> Computing. Microsoft changed the name to obliterate the history, >> [...]. SC-DOS was originally a clone of CP/M, but done for the 8086, > > More evidence of this turns up in the comment blocks within the example > drivers provided with the old MSDOS V2.00 OEM Developers disks. The example > floppy disk driver and format code mentions Seattle Computing's machine by > name and provides equates for their S100 based disk controller. > > Also, to this day, one of the magic cookie disk-type values (0xf8 thru 0xff, > found in the boot block) means eight-inch floppy -- ever see an 8" floppy on > any MSDOS machine? The Seattle Computing machine had them! > Ever see a Zenith Z-100? MS-DOS (up to 3.0) and can use 8" sloppies. Most I've seen are running 2.0, tho. (I got two Shugart 8" drives from a RS MOD 2 to run just by plugging them in. Ahh, good ol' SASI....) Pete -- Peter L. Wargo - wargopl@sun.soe.clarkson.edu, amoung others... "I don't believe it - I just spent 4 years at an expensive university- and I end up as a top-40 DJ..."
dmt@pegasus.ATT.COM (Dave Tutelman) (05/25/90)
In article <1990May23.154706.16476@sq.sq.com> ian@sq.sq.com (Ian F. Darwin) writes: >Eric S. Raymond (eric@snark.uu.net) writes a very interesting tale... >I can only add one minor quibble... ... and I'd like to add a minor quibble or two. In general, Ian's article was on the money. >In fact, dozens or hundreds of people used SC-DOS before IBM bought it from >Microsoft who in turn bought it from a small company named Seattle >Computing. Microsoft changed the name to obliterate the history... I'm un-fond of Microsoft myself, but let's be fair about motive. Microsoft bought the rights (and the code) from Seattle Computing (SC...), and the resulting product was Microsoft's (MS...). I don't think "obliterating history" was ever a consideration in the name change. >SC-DOS was originally a clone of CP/M, but done for the 8086, >the 8088's faster sibling... You're being slightly misleading about the 8086 vs. 8088 here. They're software-identical, and both chips were available in a variety of clock rates. At the same clock rate, the only difference is that the 8086 has a 16-bit bus to the 8088's 8-bit bus. Your impression probably results from the facts that: - Many 8086 machines of the era were made with the 8 MHz part, whereas IBM chose either cheap chips or very conservative design to run their 8088 at 4.7 MHz. - The difference in bus width alone makes 8086 machines run "typical" programs about 40% faster than 8088 machines at the same clock rate. >...that was becoming the CPU base of many of the >forgotten micro makers that IBM drove out of business in the first few years >of selling PC's. In fact, there were some 8086-based clones, whose market was made, not killed, by the IBM PC. Consider the AT&T PC6300 (actually an Olivetti machine). It used an 8 MHz 8086, and was as faithful a clone as most of the clones of that generation. It not only ran the software for the IBM, but accepted its (8-bit bus) add-on boards. Yes, there were a few incompatibilities, but there were similar "bugs" in other first-try clones using the 8088. Does anyone know of any other 8086-based XT clones (not made by Olivetti), or is this the only counter-example to Ian's statement? +---------------------------------------------------------------+ | Dave Tutelman | | Physical - AT&T Bell Labs - Lincroft, NJ | | Logical - ...att!pegasus!dmt | | Audible - (201) 576 2194 | +---------------------------------------------------------------+
hankd@ee.ecn.purdue.edu (Hank Dietz) (05/25/90)
In article <1990May23.154706.16476@sq.sq.com> ian@sq.sq.com (Ian F. Darwin) writes: >Many of those micro makers based their products on what was then called the >S100 bus. Early S100 systems were plagued by inter-vendor incompatibilities, Yes and no. Companies like Cromemco and NorthStar had some extensions which allowed for things like bank-switched memory (up to 512K on a z80!) and these extensions were often not compatible, but most S100 boards could pretty much be pulled from one system and stuck in another at will (although in those days the user might be expected to cut a board trace or two... ;-). The S100 boards were also a good size (not too big, not too small) and there were plenty of boards available to do interesting things like analog I/O. It was mostly the later S100 machines (e.g., 16-bit) that made the IEEE standard necessary. Ah... the good old days when machines were simple. -hankd@ecn.purdue.edu PS: The big problem I remember from way back was that timing for the parallel printer interface was not standardized so you often would have to throw a little circuit into your printer cable. This was why most of us simply avoided parallel printers back then. Serial current loop was much more standard. :-)
crmeyer@voodoo.ucsb.edu (05/26/90)
In article <4790@pegasus.ATT.COM>, dmt@pegasus.ATT.COM (Dave Tutelman) writes... > > Does anyone know of any other 8086-based XT clones (not made by > Olivetti) The Compaq Deskpro uses a 8086 running at 8 Mhz. Unfortunatly, contrary to commonly held belief, it is usually software compatable but is very picky about hardware (it HATES hercules graphics cards and EMS cards when a hard drive is installed).
pypaz@warwick.ac.uk (Larry Bauer) (05/26/90)
In article <4790@pegasus.ATT.COM> dmt@pegasus1.ATT.COM (Dave Tutelman) writes: > >>SC-DOS was originally a clone of CP/M, but done for the 8086, >>the 8088's faster sibling... > You're being slightly misleading about the 8086 vs. 8088 here. > They're software-identical, and both chips were available in Being slightly pedantic here, but there is at least one *important* software related difference between the 8088 and the 8086. The prefetch queue on the 8088 is 4 instructions and on the 8086 is 6 (or is it 6 and 8?). This may seem a trivial difference, but self-modifying code that patches itself really close to the program counter operates somewhat differently on the two machines. It also takes a long time to find this in the manuals when debugging... Who me...write self-modifying code? but that's *bad* programming practice 8-) --larry
madd@world.std.com (jim frost) (05/27/90)
bmw@isgtec.UUCP (Bruce Walker) writes: >ever see an 8" floppy on any MSDOS machine? Sure have -- I put one on the machine myself to transfer data files between an AT and a System/32. Quite a lot of fun, actually. This was in 1984 or 1985, I think. jim frost saber software jimf@saber.com
bmw@isgtec.UUCP (Bruce Walker) (05/28/90)
In article <4790@pegasus.ATT.COM> dmt@pegasus1.ATT.COM (Dave Tutelman) writes: > Does anyone know of any other 8086-based XT clones (not made by > Olivetti), or is this the only counter-example to Ian's > statement? Well, yes: the IBM PS/2 Model 30 (and 25) is an XT clone with an 8MHz 8086 that accepts 8 bit ISA boards. A few others exist; predating the IBM entry (and possibly the Olivetti) was the BEST Mark III from a small Canadian manufacturer (Exceltronics). The only really tricky part about achieving compatibility with the 8088 XT is the "bus bridging" circuit. The bus bridge decides how to handle various bus requests from the CPU to different parts of the address space. It has to "know" where there are 8 and 16 bit peripherals and how to turn a 16 bit request to an 8 bit "area" into two back-to-back 8 bit requests with proper wait-states and all.* The solution to this same problem made the AT design messier. [* I know this problem well: I helped design a single-chip gate-array for 8086 XT-clone motherboards for LSI Logic.] -- Bruce Walker ...uunet!utai!lsuc!isgtec!bmw bmw@isgtec.uucp "Remember Rule Number 79: When the tough get going, the weak get screwed." ISG Technologies Inc. 3030 Orlando Dr. Mississauga. Ont. Can. L4V 1S8
jensting@skinfaxe.diku.dk (Jens Tingleff) (05/29/90)
bmw@isgtec.UUCP (Bruce Walker) writes: >In article <4790@pegasus.ATT.COM> dmt@pegasus1.ATT.COM (Dave Tutelman) writes: >> Does anyone know of any other 8086-based XT clones (not made by >> Olivetti), or is this the only counter-example to Ian's >> statement? The Amstrad/Schneider PC line started out with some 8086 based XTs. As this is mainly a european / english effort, people in the USA may not have herd of Amstrad/Schneider. Jens jensting@diku.dk is Jens Tingleff MSc EE, Research Assistent at DIKU Institute of Computer Science, Copenhagen University Snail mail: DIKU Universitetsparken 1 DK2100 KBH O