Even more PDP-8/A weirdness (was: Re: PDP-8 diagnostics SR settings?)

Charles charlesmorris800 at centurytel.net
Sat Sep 12 11:31:31 CDT 2015

Update: The first thing I tried was removing and reseating the boot ROMs 
(465A2/469A2), since they did not use good machine-tooled sockets.
Now the boot loader performs normally, no incorrect locations, and OS/8 
boots from Drive 0 whether using the boot key or manual start at 0001. 

So of course, ANOTHER new problem shows up... OS/8 boots and runs, will run 
PFOCAL, BASIC, give directory listings...
But when I hit a Ctrl-C (for example, during a directory listing), Drive 0 
Ready goes out, the Fault lamp lights and OS/8 halts. The last instruction 
showing on the display is 07605, 6213 (CDF CIF 1).
I can hit the boot key and as soon as the drive becomes ready again, 
presumably relocating track 0, the system boots back to the "." prompt.

The DF/IF logic is on the same Option 2 board with the bootstrap and 
auto-restart circuitry. Maybe there's yet another bad connection I have now 
Time to start running diagnostics again!

I am really feeling like I'm on a snipe hunt here... sigh. This system was 
working for many years up until about 2 years ago, then it all went to pot. 

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