1dharvey@teknowledge-vaxc.ARPA (Doug Harvey) (08/03/88)
I have read that the older IBM PC/AT's can be altered to run at higher than 6mhz. Can anyone provide me with *specifics*, or pointers to such information on whether this is possible and the approximate cost. Reply via e-mail or this newsgroup. I will summarize any re- sponses I get. Doug Harvey email: 1dharvey@teknowledge-vaxc.arpa
jhunt@omews3.intel.com (Jim Hunt) (08/05/88)
In article <24213@teknowledge-vaxc.ARPA> 1dharvey@teknowledge-vaxc.ARPA (Doug Harvey) writes: >I have read that the older IBM PC/AT's can be altered to run >at higher than 6mhz. > >Can anyone provide me with *specifics*, or pointers to such >information on whether this is possible and the approximate >cost. > >Reply via e-mail or this newsgroup. I will summarize any re- >sponses I get. > >Doug Harvey >email: 1dharvey@teknowledge-vaxc.arpa It depends on the revision of the BIOS ROM in the PC/AT. Early versions would not check the clock frequency. In those machines, you could replace the 12 MHz crystal with a 16 MHz crystal and your machine would (probably) run at 8 MHz. I say "probably", because when you increase the clock speed beyond IBM's basic spec, you increase the odds of the machine not working reliably. Most machines would, in fact, work OK at 8 MHz. I believe BYTE magazine at one time published a chart showing clock frequency versus the probability that a random AT would run at that frequency. After IBM figured out that people were running their 6 MHz machines at 8 MHz (remember, IBM was planning on coming out with its own 8 MHz AT eventually), it put code in the BIOS to check clock speed. If the clock was faster than 6 MHz, it shut the machine down.
jeff@drexel.UUCP (Jeff White) (08/08/88)
> After IBM figured out that people were running their 6 MHz machines at > 8 MHz (remember, IBM was planning on coming out with its own 8 MHz AT > eventually), it put code in the BIOS to check clock speed. If the clock > was faster than 6 MHz, it shut the machine down. From what I remember reading and hearing about about IBM changed the BIOS, it was still possible to run the machine at a higher speed. IBM's speed check routine in the BIOS was only run at boot (or reset) time, so you just had to make sure that the computer was running at the original speed at that time. After boot up is complete, the machine could be shifted to the higher speed without any major complications. Jeff White Drexel University - ECE Dept. rutgers!bpa!drexel!jeff