nather@utastro.UUCP (Ed Nather) (10/22/85)
A 3rd-hand report from Motorola indicates that there exist 68020 chips
than can run with a 32 MHz clock. The yield is apparently low, but
a few (1 or 2?) are under lab test.
Can anyone confirm or deny?
--
Ed Nather
Astronomy Dept, U of Texas @ Austin
{allegra,ihnp4}!{noao,ut-sally}!utastro!nather
nather@astro.UTEXAS.EDUmdr@reed.UUCP (Mike Rutenberg) (10/26/85)
I can't answer the specific rumor, but do know that they did have plans to take the 68020 to 32+ MHZ. I wouldn't be surprised if they have been able to push some parts to that speed (esp. with cooling). Mike
gnu@l5.uucp (John Gilmore) (10/28/85)
It's certainly possible that a single 68020 in a lab can be pushed to 32MHz. It helps a lot, as was pointed out by someone from Intel in another newsgroup, to change the voltage and to cool the chip as much as possible. Getting a sample running 32MHz with freon spray on it is different from being able to produce chips that run that way across the full temperature and voltage range. But if the rumor is true, it does indicate that the chip is limited by power or temperature or fabrication tolerances (mechanical design), rather than by switching speed or electronic design. One technique usable to see what parts of the chip are limiting it is to run it at various clock rates and see what kind of failures appear. This may be where this 32MHz 68020 is being used. For example, the kind of errors that have been described on Vax 785's (carry propagation across 30 bits) might crop up, indicating that the adder is the next bottleneck. Chips run this way are not really expected to function; they're expected to point the way by how they fail. The next time the chip mask is fixed up, they can improve the adder, which probably improves the yield of 16.67MHz chips and 12MHz chips too.