[time-nuts] Data Precision 8200 Voltage Standard

Poul-Henning Kamp phk at phk.freebsd.dk
Tue May 5 15:24:49 UTC 2009


In message <20090505140906.19D4BEA2C1F8 at mailhost.idcomm.com>, "Skip Withrow" wr
ites:

>The processor in this unit is a ROMed R6500/1 (cousin of the 6502).  I fear 
>that perhaps a bit in the ROM is being read incorrectly (in the switch read 
>routine).  My guess is that there is no way to read the code out of this 
>part. 

In general, I can highly recommend that everybody try to get copies of ROM
and EPROMs of your vintage gear as backups.

If the chips are soldered in, you can avoid unsoldering them, by catching
the contents on the bus with a logic analyzer, while the ROM checksum
test runs.

A lot of HP kit have undocumented "read memory" commands that can be
used over GPIP, trick is to guess what it is called and how it works
without a ROM image to disassemble.

Poul-Henning

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.



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