Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hp-pcd!hpsgwp!plim From: plim@hpsgwp.sgp.hp.com (Peter Lim) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: 387 math chip vs. 287 math chip Message-ID: <3370014@hpsgwp.sgp.hp.com> Date: 11 Mar 91 02:36:34 GMT References: <1991Mar8.175729.8757@uwovax.uwo.ca> Organization: HP Singapore IC Design Ctr Lines: 39 / baer@uwovax.uwo.ca / 6:57 am Mar 9, 1991 / writes: $ Re: Intel 387 chips $ I understand that the 387 chip is supposed to be a big improvement $ over the 287 chip. I have heard manufacturers claim that it works $ up to 5x as fast (though some of this difference will evidently $ be attributable to clock speed differences). $ I have one data point. Running the SST test program, 287 in a zero- waitstate 12 MHz 286 machine register 280 Kilo-Wheatstones. 387 in a one-waitstate (interleaved memory) 25 MHz 386 machine register 1,200 Kilo-Wheatstones. So, not quite 5x unless you don't count the clock speed ratio :-). ... But then, I believe this program doesn't make use of 387 specific instruction either. $ Now, most of the differences above can be attributed to speed differences $ in the clock speed at which the chips were running: the 286 takes twice $ as long, but we'd expect that from a chip that's running at half the $ speed. I expected a bigger speed difference between the sx and the dx $ given the fact that the application does gobble a bit of memory -- $ after all, 456/623 = .73 -- approximately the speed ratio between $ 20 mHz. and 16 mHz. (though, in fairness, the absence of a cache for $ the dx could have slowed it down). $ Yeap ! Running MesSy-DOS at the same clock frequency, a 286 would run faster than a 386-SX because 386 machine usually has 1 waitstate unless it is a cached machine. Regards, . .. ... .- -> -->## Life is fast enough as it is ........ Peter Lim. ## .... DON'T PUSH IT !! >>>-------, ########################################### : E-mail: plim@hpsgwg.HP.COM Snail-mail: Hewlett Packard Singapore, : Tel: (065)-279-2289 (ICDS, ICS) | Telnet: 520-2289 1150 Depot Road, __\@/__ Singapore 0410. SPLAT ! #include