[Info-vax] AlphaServer DS10 470 MHz?

[David Ruben]

In article <20120122214212.09ddd495 at walker.schlensman.homeunix.net>, 
Marc
Schlensog <mschlens+news at gmail.com> writes:
>>On Sun, 22 Jan 2012 14:27:36 -0500
>>JF Mezei <jfmezei.spamnot at vaxination.ca> wrote:
>>
>>> Could it be that one department was told that model would be 470mhz 
so
>>> they built OS level config files with that model at 470, but when 
the
>>> chip actually shipped it wa 463 ?
>>
>>The DS10 was marketed as having 466MHz and that's roughly what my 
DS10
>>and the DS10ls had. The larger model was marketed as a 600 but had in
>>fact 617MHz.
>>No idea what VMS is thinking it's reporting.

A single crystal oscillator is used to generate the timing for the CPU,
memory system, and external bus. The external bus at that time was the
PCI bus. The PCI bus is required to operate at 33 MHz (actually
33.333... MHz), no more and no less. More modern busses all operate
at multiples of 33 MHz. Thus, in order to have all subsystems
synchronized, the CPU and memory must operate at multiples of 33 MHz.
This remains true to this day, for x86 computers as well as Alphas.
The DS10/466 actually runs at 466.666... MHz. The DS10/600 actually
runs at 600.0 MHz. Any other claimed frequencies are due to measurement
error, calculation error, and/or crystal tolerances.

D.R.