bilston@eniac.seas.upenn.edu (Lynne Bilston) (05/20/91)
I have a 385/25 machine, brand new, and I want to buy a maths coprocessor for it. I have seen ads in PC magazines for Cyrix and IIT coprocessors, quite a bit cheaper than intel ones. I was wondering are they REALLY 100% compatible with IBM (clone) machines, and whether you can just plug them into the existing slot like an intel coprocessor and have them behave exactly as an intel coprocessor (except faster I believe, according to the ads)?? I would appreciate any advice, Thanks, Lynne Bilston Dept Bioengineering, University of Pennsylvania bilston@eniac.seas.upenn.edu
scotte@locus.com (Scott D. Eberline) (05/21/91)
In article <43523@netnews.upenn.edu> bilston@eniac.seas.upenn.edu (Lynne Bilston) writes: >I have a 385/25 machine, brand new, and I want to buy a maths >coprocessor for it. I have seen ads in PC magazines for >Cyrix and IIT coprocessors, quite a bit cheaper than intel ones. >I was wondering are they REALLY 100% compatible with IBM (clone) >machines, and whether you can just plug them into the existing >slot like an intel coprocessor and have them behave exactly as >an intel coprocessor (except faster I believe, according to the >ads)?? I've been told by a few kind people on the net (thanks, kind people!) that Cyrix coprocessors (probably the 83C87) cannot run asynchronously. This is really only important if you wish to run the coprocessor at a different clock speed that your CPU; for example, your 25 MHz 386 can work with a 387 running asynchronously at up to 40 MHz. Cyrix and IIT coprocessors are supposed to conform to the IEEE floating- point specification, as do the Intel chips. They may not produce exactly the same results in the least-significant bits as Intel for some operations, but this does not mean that they are incorrect -- they may be more precise than the Intel results. But all three should produce results correct as far as the IEEE specifies. A few questions I'd like to add: are Cyrix coprocessors, particularly memory-mapped coprocessors such as the EMC87, enough faster than Intel chips that a Cyrix EMC87 running synchronously at 25 MHz would beat an Intel 80387 running asynchronously at 33 MHz? 40 MHz? Is the EMC87, like the 83C87, incapable of running asynchronously? Does anybody have a phone number for Cyrix? -- Scott D. Eberline scotte@locus.com or lcc!scotte
sci240s@monu6.cc.monash.edu.au (mr w.j. ho) (05/21/91)
scotte@locus.com (Scott D. Eberline) writes: >like the 83C87, incapable of running asynchronously? Does anybody have >a phone number for Cyrix? The 83D87 User's Manual says Cyrix address and tel is as the following: Cyrix PO Box 850118 Richardson TX 75085-0118 Tel: (214) 234-8387 >-- >Scott D. Eberline scotte@locus.com or lcc!scotte -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^ Wey Jing Ho Tel: 61-3-5732567 E-mail : sci240s@monu6.cc.monash.edu.au ^ ^ Physics Dept., Monash University ( Caulfield Campus ), Melbourne, AUSTRALIA ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
pjw@hpctdkr.HP.COM (Peter Walsh) (05/22/91)
>/ hpctdkr:comp.sys.ibm.pc.misc / bilston@eniac.seas.upenn.edu (Lynne Bilston) / 9:55 am May 20, 1991 / >I have a 385/25 machine, brand new, and I want to buy a maths >coprocessor for it. I have seen ads in PC magazines for >Cyrix and IIT coprocessors, quite a bit cheaper than intel ones. >I was wondering are they REALLY 100% compatible with IBM (clone) >machines, and whether you can just plug them into the existing >slot like an intel coprocessor and have them behave exactly as >an intel coprocessor (except faster I believe, according to the >ads)?? >I would appreciate any advice, >Thanks, >Lynne Bilston >Dept Bioengineering, University of Pennsylvania >bilston@eniac.seas.upenn.edu >---------- You can call Cyrix Corp. toll free at 1-800-848-2979 and ask for their Compatibility Report and their Benchmark Report for any of their chips. I purchased their SX version of the 387 and dropped it right into a Taiwanies clone and have had no problems at all. You might try looking at the Dec. 1990 issue of PC-World, I think there is a review of 387 compatibles. Peter J. Walsh Hewlett Packard Colorado Telecommunications Divsion pjw@col.hp.com
quimby@madoka.its.rpi.edu (Quimby Pipple) (05/22/91)
We've used Cyrix x87's in 386/25's without any compatability problems. They pass every 387 diagnostic I've seen, and they run a Savage benchmark about twice as fast as an Intel. Quimby -- quimby@mts.rpi.edu, quimby@rpitsmts.bitnet -- quimby@mts.rpi.edu, quimby@rpitsmts.bitnet