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Re: Uther card works on Apple IIplus with contiki
Glenn Jones wrote:
Even though the 6502A is a 2MHz part it is still run @ 1MHz. The
difference is in the tolerances for setup and hold times. the table in
this url explains it
>http://web.pdx.edu/~heiss/technotes/aiie/tn.aiie.04.html
Whats confuses me a bit is the rockwell datasheet that I have indicated
my CPU is a 1Mhz part as it does not have a letter designator (A or B
for 2 and 3Mhz respectivly).
So if I really have a 1MHz rockwell part, I am back to square one on why
one cpu works and the other doesns't.
Glenn
Glenn,
Back in the old days parts were often "graded" and labeled based on the
speed that they were capable of. If they harvested enough high speed
parts to meet demand they would stop testing at that speed. Rather than
degrade the price premium for high speed chips then number labeled would
be limited to the number they could reasonably sell. As the production
runs progressed yields would generally rise and the number of high speed
capable parts would increase, sometimes faster than demand. It's
entirely possible that many chips labeled as 1MHz will actually run at
higher speeds, sometimes much higher. In the case of the 6502 I don't
think there was ever a lot of demand for 2 MHz parts compared to 1MHz parts.
--
Rob
"Never ascribe to malice that which can be adequately explained by
stupidity"