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From: f89ba@rigel.efd.lth.se
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Frequency measurement on AT-bus
Message-ID: <00939B9E.AB755D40@rigel.efd.lth.se>
Date: 16 Jul 90 01:05:36 GMT
Sender: newsuser@lth.se (LTH network news server)
Reply-To: f89ba@rigel.efd.lth.se
Organization: Lund Institute of Technology,Lund, Sweden
Lines: 23

I have a 12 MHz AT-clone with a SUNTAC chipset. The documentation
is rather poor, and I need to know to things:

   * What clock frequency the 80287 uses (I plan to install one,
     but don't know what frequency it runs at)
   
   * What clock frequency the bus is running at (probably 6 or 8 MHz)

I realize that the only way to get this info. is to measure the 
frequency. I have access to the neccessary instrument (a counter),
but I'm not sure if it's safe to connect it to the signal lines
mentioned above. The counter's input is rated as 1 MOhm in parallel
with 25 pF, which would mean an impedance of 600 Ohm at 10 Mhz.

Should I use some sort of buffer between the signals and the counter?
What would this circuitry look like?
I would like as many details as possible, because I'd hate to
damage some part of my computer.

Thanks in advance
   
   Bengt Ask, Lund Institute of Technology, Lund, Sweden