DoN. Nichols wrote:
According to Christopher Tidy :

Too_Many_Tools wrote:

snip

While I have not seen the time keeping circuitry of a SUN station, I
would wager that they had a small oven for the oscillator that kept the
quartz crystal at a stable temperature.

Out of curiosity I downloaded the data sheet for the "Timekeeper RAM"
M48T59Y chip. It is quite a sophisticated device. Frequency accuracy is
better than ~20 ppm between 0 deg. C and 50 deg. C. That equates to a
maximum error of about 50 seconds per month. It also incorporates a
calibration feature through which the clock can be speeded up or slowed
down according to a 5-bit number loaded into a register. This apparently
brings the accuracy to within 2 ppm at 25 deg. C. It's a neat device. I
guess you get what you pay for - you don't find a £20 clock chip on a
£50 motherboard. Whether Sun use the calibration feature on the chip I
don't know. If anyone knows please let me know. I'm curious.


Among the options to the "date" command, which can both read
and display the date, and set it, is:

================================================== ====================
-a [-]sss.fff Slowly adjust the time by sss.fff seconds
(fff represents fractions of a second). This
adjustment can be positive or negative. The
system's clock is sped up or slowed down
until it has drifted by the number of
seconds specified. Only the super-user may
adjust the time.
================================================== ====================

So -- yes, Sun does use the speed control.

Ah yes. Thanks Don. I read about this some time ago, but have never
actually used it. Now I wonder if the machine uses the speed control
automatically (this is mentioned in the chip data sheet) to correct
deviations of the clock?

Best wishes,

Chris