DEC PDP11/23

*Link back to main site PDP1123

*Pictures of my PDP11/23

I got this machine back in 1992 out of a basement of a computer technology firm.

H9270, A 18Bit Base Q/Q, 4 rows of 4x4 Dual Cardholder date 1980, with power supply.

M8186 CPU board (No Floating point processor)

M8047 first one with 16K MEM ,2x I/O Ports and 2 Bootproms containing RX02/RL02 and after rewirering a Boot from TU58 (Serial Tape Streamer)

M8047 second one with 16K MEM ,2x I/O Ports

M8029 The RX02 Floppy Driver.

The RX02 a 8 Inch Dual floppy drive Unit.

VT100 Terminal and a VT420 (also a defective VT103-Bad Line transformer)

Some 8" FFD's . 3 with mentioned containing Boot options RT11.

Over the years I tried many times to get the machine running again, but no luck.

Just a ODT (Terminal mode),could enter with the terminal a RX02 Bootstrapcode but the only thing from the RX02 drive was a click of the head.

Made lots of debugging on that RX02, Thought that must be the problem.

Jan 2014:

Than at a sell action of the "Correct Radio Museum Rotterdam", I came in contact of someone that also has a PDP11 machine.

Talking about my problem he suggested to find online the TU58 emulator of which could be run on a normal PC and being a serial Tape Unit of origin there is not to be the need of a special driver card installed. Just a free serial is enough.

So I found the download of the TU58em.

Did a long search over the Internet of How-To make a booting emulation tape

of RT11. But in the end it became all clear how to use the TU58 emulation.

Rewired the M8047 to Boot the second loader in the PROM that supposed to contain the TU58 Bootloader.

Then the great moment of running it on the PDP1123.

Nothing happened...

Ok I had to manually type in the TU58 Bootstrap code on the terminal.

a 1000G, and then....

That's more like it. A Boot prompt after 23 years.

But after a DIR command, halfway the listing there is an error code.

?MON-F-TRAP to 4 012230

That must be a memory address that has a problem.

So in ODT I typed a few memory allocations and fill them with some

number.

Then look back into the address location and noticed something is wrong.

At location adres 012230 I typed in 077400

Looking back in to it it contained 076400, notice the "6" instead of "7".

So Bad memory.

Have to debug that and replace some Memory IC's.

To be continued.