PDP-8/I at the RICM

Michael Thompson michael.99.thompson at gmail.com
Sat Jan 10 18:53:58 CST 2015

We did more debugging on the PDP-8/I today. The individual CLA and CMA
instructions work OK, but the combined CLA CMA instruction does not set all
of the AC bits to 1s. Tracing with a 'scope found that the AC ENABLE signal
was not active during the combined CLA CMA instruction. Replacing the M160
in slot E30 fixed the missing AC ENABLE signals and fixed the combined CLA
CMA instruction. The Instruction Test 1 and Instruction Test 2 diagnostics
ran OK, so the processor is probably working fine. The TC01 DECtape diags
did not run as expected so we need to read the manual before we try it
again next week

Michael Thompson

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