Re: Uther card works on Apple IIplus with contiki

["Michael J. Mahon" <mjmahon@aol.com>]

Rob wrote:
> 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.

It's still true today--that's why overclockers have so much fun.  ;-)

-michael

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