[pups] Default P11 Emulator Clock Rate

Steven M. Schultz sms at moe.2bsd.com
Thu Oct 5 08:27:58 AEST 2000

Hi -

> From: Frank Wortner <frank at wortner.com>
> The default clock rate on P11 is 50 Hz.  While this corresponds to AC line
> frequency in many parts of the world,  it is not correct for the
> U.S.,  where 60 Hz is the norm.  Since PDP-11 Unix was developed in the
> U.S.,  the bootable distributions probably assume a 60 Hz clock

	Yes, the bootable 2.11 distribution assumes a 60Hz clock.  That is
	easily changed though for folks that live in 50Hz areas.  Edit the
	kernel config file and change LINEHZ to 50.  The rest of the system 
	has been changed to ask the kernel for the clockrate so there shouldn't
	be any compiled in assumptions outside the kernel (if I overlooked
	any let me know and I'll fix it).

> My emulated 11 had difficulties keeping accurate time until I discovered
> the 50 Hz clock rate.  After I changed it to 60,  the emulator's time was
> remarkably accurate!

	Indeed it is accurate.   Earlier versions of P11 would lose time
	very rapidly if the PDP-11 was "busy" - but the latest version of
	P11 is fantastic at keeping time.  If you run 'ntpd' on the 11 the
	time stays even closer to "real".

	Steven Schultz

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