More XXDP and ODT Testing

Since my previous XXDP capers, I'd set up the VT220 with a proper 25-pin serial cable. This left me with enough 9-pin adapters to run the VT200 and the TU58 emulator at the same time. Using a period terminal gives a totally different impression than a PC terminal emulator which, if it wasn't for the the whir of the cooling fans, seems just like running a PDP-11 emulator on the PC. With the real terminal, the PDP-11 seemed much more like a stand alone machine which just happened to be connected to a PC. The reliability problems I was experiencing before have disappeared, which is encouraging. I may even try cranking the speed of the virtual TU58 up, but the only faster speed supported by the MXV11 is 38.4 Kbps, so I'm not sure it'll handle it.

I was now also armed with the XXDP Handbook [available from Bitsavers under /pdf/dec/pdp11/xxdp/ - please use a nearby mirror] which explains what the diagnositcs actually do and any options you may need to input. Unfortunately it doesn't say all that much about the more cryptic output of the programs, should errors be reported. In any case, I ran a few tests again with different options (for example to disable particular tests which you know are going to fail or take a very long time to run) and got better results than before. I'm reasonably confident the CPU, MXV11 and memory are working correctly.

Whilst getting things running after breaking out of failed XXDP tests, I figured it was high time I read up on the finer points of ODT. The CPU User Manual [on Bitsavers: /pdf/dec/pdp11/1173/KDJ11-A_UsersManual.pdf] contains a good guide to get you started. There are very few commands but every single keypress makes a difference, and not always the difference you wanted it to make.

After reading up I remembered I'd once seen a page of short test programs which can be toggled (or typed, in the case of ODT) in to run some simple tests. That page is here and, although it's really meant as a troubleshoting guide, it was fun to type in and run a few of the programs.

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