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RE: [rtl] Stability Problems while generating 1KHz signals




For some info on the 8253/4 try "Interfacing to the IBM Personal Computer"
by by Eggbrecht

Dan

-----Original Message-----
From:	Hermann Lauer [SMTP:Hermann.Lauer@IWR.Uni-Heidelberg.De]
Sent:	Friday, October 09, 1998 6:37 AM
To:	yodaiken@chelm.cs.nmt.edu
Cc:	rtl@rtlinux.cs.nmt.edu
Subject:	Re: [rtl] Stability Problems while generating 1KHz signals

Hello List Readers,

I dug into the RTlinux code meanwhile and maybe I now understand the most
relevant parts of the code (Is there a programming sheet of the 8254/8253
available on the net somewhere and a schematics of the wiring of the counters
?).

I defined the debug code in RTlinux0.9 9F (which measures the ticks while
setting a new counter value?) and come up with the following numbers:

66 MHz pentium:  new record: 02 31b
166 MHz pentium: new record: 0a 0c
66 MHz 486:	 new record: 13 48

So the 66 pentium is very bad - it seems to take somtimes more than a half
period of decimal 500 to set the counter 0 !

The chips on the 66 MHz pentiums motherboard are: S82433/4LX (3 chips) and
S82378ZB

So I should just give up with that motherboard - or what do you think ?

Thanks for any further ideas/suggestions/help.

Greetings

   Hermann
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