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And note a significant portion of that code is the M9312 processor 'diagnostic test code' that could logically be pruned out. Only about half the code does the ODT function.

Well, I would measure the min/max voltage at each and every pin, preferably dynamically on a scope. Should never be much above 5.5V (assuming 5V VCC) nor below -0.5V. Severe overshoot/undershoot could cause excessive power dissipation. If the chip is in a socket it might be possible to lift the...

Space available to add a heatsinks on top of the suspect chips? Like this: https://www.digikey.com/en/products/detail/assmann-wsw-components/V5618B/3511499

I don't know exactly what PDP-11 and boot mechanism you are using, but generally speaking the answer is yes. For example, on a unibus PDP-11 with the M9312 DX bootstrap prom, you can enter either DX0 or DX1 at the prompt to select the boot unit.

Try this: https://github.com/AK6DN/rx02_emulator/blob/master/disk_images/RT11.RX1

"Extended March C-" is what I based the test strategy of my MEMX memory diagnostic on. In the attached pdf, see pp. 48-53 for a discussion about MARCH testing algorithms. Rest of presentation is pretty useful too as a overview of memory failure characterization and testing strategies. PDP-11...

177456 is the RC11 disk controller data register RCDB per PDP11 processor handbook. Will timeout access trap on your system (or it should).

And while you are spending all your crypto profits on that PC04, you can pick up this too ... https://www.ebay.com/itm/126379476903 PDP-8m front panel plex for $600...

It certainly is true that if you have no working memory you can move to cover the physical 0-8KB or so address space loading and running any memory test diagnostic is problematic. Some systems have very basic memory test functions in ROM that could be used as a simple memory test facility. Or in...

My bad. Correction: it DOES require a PDP11 with memory management, so 11/03-04-05-15-20 are not supported. 16KB is the minimum required memory. Memory management is used to relocate the program image to more easily test the low 8KB memory as well as all the memory above the 56KB boundary.

FYI I have my home grown memory diagnostic I use for checking my 11/34 and 11/44 systems. Requires only a bare minimum of the first 8KB to be working, and will test a fully loaded 18b or 22b memory configuration. It is not system specific, and will run on anything from an 11/03-04-05 thru an...

This one?

My DEC replacement parts notes indicate a D664 can be replaced by a 1N3606 (older and hard to get) or a 1N4153 (still available from many sources).

The 11/20 was the only member of the series that was NOT microcoded. I don't believe there is even one PROM in the 11/20 design. Just logic ICs. An 11/04 or 11/05 is a simpler/smaller design, but the tradeoff is they are microcoded and make heavy use of small PROMs for decode logic. Also none...

I have a couple of VAX 4000 VLC boxes. Both started misbehaving a bit recently (run for a while then reboot). Noticed the boxes were getting really warm. Opened them up, and found the fans on the power supplies had stopped rotating. Boxes ran fine opened with external fan blowing into the power...

It does, but they are contained within TU58 (or RX02) XXDP .DSK images files. One could use my xxdpdir.pl program to extract all the files from an XXDP image (available here: https://github.com/AK6DN/xxdpdir I use that program to extract all the files from the RL02 distribution media and then...

So this is completely different than how an RX01/RX02 drive itself implements 12b vs 8b mode storage on RX01 or RX02 media. In 12bit mode in the RX drive controller, each three consecutive 8bit media storage bytes (totaling 24bits) is then used to store two 12bit words. Only 3/4 of the media...

Re: RX01/02 sector ordering: http://gunkies.org/wiki/RX01/02_floppy_drive#Layout

Someone could certainly develop a new microcode file for the ZuluSCSI (or even SCSI2SD I guess) and you could just drop a new SCSI tape emulator .bin fine on the SD card and away you go. The full sources are here: https://github.com/ZuluSCSI/ZuluSCSI-firmware for the SCSI disk support. Just...

The 1N645-1 at DigiKey is a current production part from MicroChip (MicroSemi subdivision), so its lineage is not an issue. Or 1N645 from NTE at DigiKey: https://www.digikey.com/en/products/detail/nte-electronics,-inc/1N645/11644785 for US$2.22 each. The 1N3606 however appears to be...