Tuesday, February 7, 2012

Console printer/keyboard

Today I did a little work on the console printer/keyboard to-be (a Tekade teleprinter used by the German armed forces). The power supply had a problem in the main 5v regulator. This consists of two LM317's in series with an op-amp driven feedback loop. I found out that both LM317's and the op-amp were broken (culprits shown right); possibly an over-current issue. I replaced those parts, and got the juice running again.
The teleprinter is running again (at least, in local mode). To connect it to the pc, I'll either need to build an RS232 to current loop converter, or try to find the V.10 interface card that was an option on these machines.
On the inside, these machines are a pleasure to work with. All functional units (power supply, keyboard, printer) can be removed by unscrewing 2-4 screws. The electronics are contained in a card-cage (three intel 8749 microcontrollers, CMOS logic, and high power transistors to drive the mechanical parts).

Functionally, it's equivalent to a Teletype ASR, with a paper tape punch and reader:

Sunday, February 5, 2012

Video: OS/360 IPL up to IEA100I message

After Chris Bigos (www.ibm360.info) put large parts of the 7201-02 Field Engineering Diagrams Manual online, I had enough information to get a little further again.

I estimate that the cpu emulation is now about 70% complete. (out of 513 uops, 346 have been implemented completely and correctly, another 36 have been implemented and are probably correct, 32 are partially implemented, and 114 have not been implemented). Of course, the remaining 30% is the toughest part, though some of the uops probably will never get used because they're specific to the 9020's CE (7201-02) inter-processor communications and FAA special instructions.

I've had to use a few kludges, such as inserting uops into the microcode, keeping track of what the instruction counter should be, and faking the division and multiplication instructions, because some of those details are still vague. They should become less vague now that Chris has also put up the Field Engineering Theory of Operations Manual.

I've modified the "plain" Hercules emulator to write  register values and a memory checksum to a text file after each instruction, and I'm doing the same in the M65 emulator. By comparing the text files, discrepancies between the emulators show up. The M65 emulator generates a second (huge) textfile that show the uops that get executed. I find the offending instruction in that second file, and try to figure out what causes the behavior to be wrong.

This way, I'm now getting correct behavior IPL'ing OS/360 MFT up to the first message being written to the console. The console is an emulated 1052. The printer/keyboard has been replaced with a serial terminal in this emulation.

I would like to connect a 1052 to the emulator; that would make the interaction a lot more realistic. However, I think getting my hands on a real 1052, and somehow interfacing it to a PC is going to be difficult. I do have a german teleprinter (Telex), so I'm thinking of building a converter between RS232 and current-loop to hook that up to the pc running the emulator. I'll need to fix the teleprinter's power supply first though.

Well, enough said for now. Here's the video: