25 Sep
2016
25 Sep
'16
9:34 p.m.
On Sep 9, 2016, at 8:17 PM, Jerry Weiss <jsw at ieee.org> wrote:
On Sep 9, 2016, at 6:11 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
That?s a very good piece of information, I hadn?t considered that. I have 11/73.
I?ve checked the memory with ODT and can confirm the stuck bit.
Finally got back to this. First clipped VCC on the suspect
and confirmed that the bank and address range was the same as the original error.
So finally pulled out the soldering iron and replaced as chip. Back to memory test
and all is now good.
R VMJA??
VMJAB0.BIC
CVMJAB0 ECC/PARITY MEMORY DIAGNOSTIC
11/83 CACHE AVAILABLE
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I board fixed, one to go. Thanks for the support.
Jerry
If your CPU is an 11/73 (which can directly
'access' [hate that verbism
:-] all of memory from ODT, unlike the 11/23 which is restricted to the
bottom 256KB), try playing around with a failing location, and its
alternative, directly, and see if a store of random data into one can be
read back directly from the other
Note: The 11/'73' CPU powers up with the cache enabled, even for ODT!
So if you write xxx into some location, if you then read it back, you will get
the correct data even if the memory location is busted - the CPU is getting
the (correct) data from the cache. To have your 'memory' reads and writes
actually go to the memory, you need to turn off the cache:
17777746/ 02000
Note that starting the machine does an INIT, which will again enable the
cache.