i8355 from SDK-85 flakey

robo351 robo351 at verizon.net
Mon Apr 26 08:21:47 CDT 2010

Hi Chris,

Freeze spray fixes usually give one additional troubleshooting information
but I've never seen a case where the component continues to work until power
is removed.

I suspect you are dealing with a reset, clock or timing issue as the
component powers up.  Many Intel parts were very particular about their
signals on power-up so you might see if your timings and DC power ramps are
within specs.


-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Chris Elmquist
Sent: Saturday, April 24, 2010 8:23 PM
To: Classic Computer Tech
Subject: i8355 from SDK-85 flakey

I obtained an Intel SDK-85 eval board some time ago and decided to try
to bring it back to life today.  It had been part of a Philips logic
analyzer demo system apparently.  They had cut off the prototyping area
on the left side and put their own board there instead... which had a
2716 EPROM on it and some hardware to generate glitches as part of the
logic analyzer demo I guess.

In any case, I undid all of their mods (except of course, putting the
sawed off prototype section back on!) and the unit sort of works.

What I have discovered is that the 8355 ROM+IO chip is flakey.  It won't
work unless I freeze it with component cooler.  Once I have done that,
then it starts working and stays working for hours as long as power is
not removed.  If it gets powered down, then I have to freeze it again
before the device will respond with valid fetches.

I don't suppose anyone has a spare 8355 with SDK-85 monitor burned in
it do they? 

I'm guessing that's probably unobtainium so, failing that, wondering if
there's a .HEX of the ROM image floating around so that I don't have to
type it all in.   If I have the bits, I can burn a 8755 that drops into
the same location.

Any guesses as to what the failure mode might be of the 8355?  It is sort
of curious that once it gets started from frozen, it keeps working nicely.

I already did my time at ETA, cooling chips in liquid nitrogen so that's
kind of behind me now ;-)


Chris Elmquist

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