pdp8/e Problems: KE8-E EAE debugging

Ethan Dicks ethan.dicks at gmail.com
Thu Mar 10 19:01:52 CST 2005

On Wed, 09 Mar 2005 20:43:12 -0500, Charles H. Dickman
<chd_1 at nktelco.net> wrote:
> I added support to SPCWR3.PA for the VC8/I.
> http://www.chd.dyndns.org/pdp8/VC8/SPCWR3_vc8i.PA

Nice!  Thanks!
> This requires an EAE and now I find out that my untested EAE does not work.

Doh!  I didn't even think of that.  :-(  I don't have a single EAE for
_any_ machine.

The closest I could think about getting would be to bum some M-series
boards from a working machine/disk controller and stuff them in my -8/i,
but ISTR there are a few wire changes to make as well, so I think I'd
rather not do that if I thought I'd have to remove it.  In any case, I don't
have a genuine VC8/I in the first place, or it might be attractive to try.

Ah, well... maybe _someday_ I'll run across the parts I need to pull this off.
> I got a copy of MAINDEC-8E-D0LB-D which is EAE test 1 and it locked up
> pretty much the same way. I removed the EAE and the diagnostic halted at
> a reasonable place insteading of locking up.

Sounds ominous.
> This not gonna be easy to fix. The over-the-top connectors prevent the
> use of an extender card, so I can't probe anything easily.

I don't know if you have access to any DEC module blocks, but it might be
possible to rig up a flexible over-the-top connector if you have a couple of
single-slot wire-wrap connectors and some wire-wrap wire.  

Alternately, if you have some single-height proto cards, one could manufacture
a couple of over-the-top extension cables, space the CPU out two more spaces,
put the EAE board under test in the middle of the three blank spaces on a quad
extender, and hang one paddle card upside down under each over-the-top connector
to route the signals a few inches in the air over some ribbon cable...

Hopefully, you can envision this arrangement.  Write me offline if it's not
clear enough and I'll try to describe it better.

I don't think any of these signals are critical enough that a couple of ns of
wire is going to cause any problems.
Unfortunately, I can provide no insight on the EAE fault itself; I
have no experience
with it.


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