• Please review our updated Terms and Rules here

Search results

  1. Alois54

    IBM 5162 Weird CPU reset

    Just a quick update on my problem : I have finally bought a 32-bit 100Mhz logic analyzer (a Digilent Digital Discovery) Using this nice instrument I have discovered a first fault : bits 11 and 15 on the data bus (D) were disconnected between the CPU and U100. After a bit of soldering, now the...
  2. Alois54

    IBM 5162 Weird CPU reset

    I have a theory : On the 5162 the /ARDY signal is used for RAM cards (0xA0000-0xDFFFF) and for I/O channel (0x100000-0xFDFFFF) and the /SRDY signal is for onboard RAM and ROM. So grounding the I/O CH RDY signal would only stop the CPU when trying to access addresses associated to the /ARDY...
  3. Alois54

    IBM 5162 Weird CPU reset

    Thanks a lot for your help. Could you also check step 4 of the procedure ? Because my CPU sometimes stops after a few cycle, so if you have address 0xFFFFF0 on the ISA bus like [here] it would mean your CPU stopped on the first instruction (not like mine). :)
  4. Alois54

    IBM 5162 Weird CPU reset

    I completely agree! Now I have to understand why the other 5162 tested with this procedure didn't need the DWAIT0 signal tied to ground to stop executing the BIOS code on boot... :unsure:
  5. Alois54

    IBM 5162 Weird CPU reset

    Yes, exactly! In the 5162, /ARDYEN and /SRDYEN are connected together to the -ARDYEN signal witch comes from a /Q output of a flip-flop, the D input of said flip-flop is tied to the "DATA CONV" signal from U27 (some sort of glue logic chip/rom ?). I don't know if this is normal, but my -ARDYEN...
  6. Alois54

    IBM 5162 Weird CPU reset

    First, thanks modem7 for your input, I really hope we'll be able to fix this 5162 :) I've checked and my +REFRESH is low on boot, it was just a bad assumption I had before analyzing the complete status of WAIT0 for all addresses in U90. Maybe your procedure is correct and we're still after the...
  7. Alois54

    IBM 5162 Weird CPU reset

    OK, I have analysed the status of the WAIT0 bit of U90 for every input address and it goes like this : If +REFRESH is high, WAIT0 will always be high. If +REFRESH is low, the status of WAIT0 depends on the value present on the address bus and the jumper J10 : If J10 is low then : 0x0-0x7FFFF...
  8. Alois54

    IBM 5162 Weird CPU reset

    Well, I've disoldered U90 on my motherboard and I have some news 😅 I tested it in my TL866II+ using a hand made .LGC file and O2 bit (WAIT0) is working fine. (and I'm starting to think nothing was wrong with this bipolar PROM...) I'm going to analyse the truth table for this bit to try to...
  9. Alois54

    IBM 5162 Weird CPU reset

    No protection of any kind, this type of ROM can be read easily, however they do need a special programmer to be programmed because of the very specific voltage&curent required...
  10. Alois54

    IBM 5162 Weird CPU reset

    OK, so sourcing a new old stock Bipolar PROM seems to be easy, finding someone to program it is a bit harder BUT finding a dump of a good U90 seems impossible. 😨 Does anyone have a dump or could make a dump of this PROM ? Maybe the dump of U72 in a 5170 might be compatible but I can't find one...
  11. Alois54

    IBM 5162 Weird CPU reset

    Thanks for your help. I tested tying DWAIT0 to ground with a 25ohms resistor (pin 18 on U14) and now the CPU behave has expected on reset with the ground I/O CH RDY procedure. Even better I can see the correct data on the CPU data lines at this state. ("0x65EA" in my case because I'm using...
  12. Alois54

    IBM 5162 Weird CPU reset

    Do you think forcing +5v won't overload and fry the open collector of the /READY pin of the 82284 ? I'm afraid of lifting the /READY pin of the 82284 to test this...
  13. Alois54

    IBM 5162 Weird CPU reset

    Hi, Thanks modem7 for your answer (and for the great minuszerodegrees.net site ;)) Yup, I found out that after posting my message. I'm pretty sure your procedure is correct 🙂 because when the CPU finally stops I get the expected state, now I have to find why it doesn't do that immediately on...
  14. Alois54

    IBM 5162 Weird CPU reset

    Hello Everyone, I'm currently in the process of troubleshooting my IBM PC XT/286 5162 which doesn't boot or beep with the stock ROMs. When trying with SuperSoft diag BIOS, sometimes I get no beep at all, sometimes it will start beeping completely erratically (like there are random resets every...
  15. Alois54

    IBM 5170 post code 201

    Hi ! I'm having some difficulties repairing my 5170 (type 3), let me explain : At boot, it is always displaying the code 000000 FFFF 201 and hangs there. If I boot it with supersoft diag roms, everything looks okay (with the same quirks as described on minuszerodegrees.com) I've tried...
Back
Top