[Info-vax] AlphaServer DS10 470 MHz?

[ChrisQ]

On 01/22/12 15:04, VAXman- @SendSpamHere.ORG wrote:
> In article<jfh83v$35m$1 at reader1.panix.com>, JohnF<john at please.see.sig.for.email.com>  writes:
>> In comp.os.vms VAXman- wrote:
>>> I suspect that it's far easier to accurately measure the clock speed than
>>> it is to try to measure the zero-crossings accurately for cycle-time.
>>
>> Just curious -- I was wondering about that: isn't the cpu driven by
>> an (onchip or onboard?) oscillator of some sort? If that's the same
>> oscillator that drives the clock, then it's always going to measure
>> the "correct number" (i.e., however many cycles it's programmed to
>> count as a second) -- you can't know if your clock is running slow
>> by looking at that same clock.
>
> Some are; some are not.  I recall when upgrading my AlphaStation-200 4/166
> to an AlphaStation-200 4/233 that not only was its Alpha chip replaced but
> it also required a clocking module replacement.
>

There will be clock multiplier / pll and routing circuitry on chip, but 
all micros
i've ever seen are clocked from an external oscillator, usually a dil 
crystal
oscillator module for accuracy and stability.

Have never heard of a crystal oscillator on chip, though many embedded 
micros have
a fixed frequency, moderate stability oscillator on chip for cost sensitive
applications...

Regards,

Chris