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Thread: How to read parallel-port POST diagnostic codes?

  1. #81
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    Thanks for the reply, and the advice help regarding the error codes.

    Sounds like I'll go ahead with attempting to swap the DMA chip out. But I知 probably going to practice de-soldering a bit first. If that doesn't work I'll look at the memory.

    I've got a temperature controlled soldering iron, but will still probably go for the cut the chip out and then de-solder the legs separately approach. As I知 not sure I値l be able to get all 40 pins molten at the same time.

    Alternatively I might considering picking up a cheap Hot Air re-flow gun, and following the technique outlined here:
    http://hackaday.com/2016/01/12/desol...es-like-a-pro/
    But I知 not sure how well it would work on a 40-pin IC. Although the video makes it look very easy to de-solder memory chips.


    I'll also probably remove the leaky battery at the same time, especially since there are concerns about it's affect on the motherboard. I'm assuming the system should run fine without a battery, until I can get round to replacing it.

  2. #82
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    Additionally to the solder iron you must have a desoldering pump. Also a needle fixed at the end of a chopstick (the wodden sticks chinese peoples use instead of fork/knife) is usefull. With that you can feel and hear if a pin is well desoldered.

  3. #83

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    Quote Originally Posted by AlG View Post
    As I知 not sure I値l be able to get all 40 pins molten at the same time.
    You won't. If you don't have something like a desoldering station or desoldering pump (Google both if you're not certain), then use your method of cutting the legs (close to the body) and pulling each out as you reheat them. You'll need to clean the holes before inserting the new chip and re-soldering.

  4. #84
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    Feb 2010
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    Russia, St.Petersburg
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    Sorry for offtopic.

    Does anyone have a XT BIOS or Testing ROM sourcecode with LPT or 0x80 diagnostic output ? AFAIK, IBM XT original BIOS (available in sources) does output to port 0x60 but diagnostic code points are very "coarse". I did not find XT BIOS sourcecode with 'modern style' output to port 0x80. I have a dead XT board, it initializes PIT and DMAC (I see a correct DMA0 pulses for DRAM regeneration) but hangs before first 64K test and video initialization.

  5. #85
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    May 2006
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    Melbourne, Australia
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    Quote Originally Posted by alecv View Post
    Does anyone have a XT BIOS or Testing ROM sourcecode with LPT or 0x80 diagnostic output ? AFAIK, IBM XT original BIOS (available in sources) does output to port 0x60 but diagnostic code points are very "coarse". I did not find XT BIOS sourcecode with 'modern style' output to port 0x80. I have a dead XT board, it initializes PIT and DMAC (I see a correct DMA0 pulses for DRAM regeneration) but hangs before first 64K test and video initialization.
    Are the Supersoft/Landmark Diagnostic ROMs [here] not suitable for you ?

  6. #86

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    I've finally been able to get back to this project.

    It looks like the PSU in my 6300 is indeed on its way out and may have been the cause of my problems, instead of the battery leakage. I've hacked up a Dell PSU to give me the +5, +12 and -12 volt outputs.

    I have 2 6300 motherboards, one with ROM 1.21 and the other with 1.43. On the 1.21 the LPT code reader outputs a 43 then a 45 and the previous/next buttons don't do anything.

    On the 1.43 I see 43, 44, 45, 48, A5, 3F. Using the prev/next buttons I can cycle between the last 3 codes 48, A5, 3F. That's good news based on the codes listed in an earlier comment.

    I'm going to connect the hacked PSU a little more securely, then replace the EGA video card and keyboard and see if I get any output on the display.

  7. #87

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    Progress??

    I installed the EGA card and keyboard and fired it up.

    IMG_1586.jpg

    For. Exactly. One. Boot....

    Subsequent restarts give me code 43, 44, 45, keyboard lights keep flashing, nothing on the display.

    So if I understand the codes from previous posts correctly:
    On the 1.21 ROM motherboard since it display 43 and 45 without displaying 44 - the first 64K RAM may be bad?
    Any hints on what to look for if it stops at 45 on the 1.43?

  8. #88
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    I'm confused; you said EGA card, but I see the AT&T monitor in your screenshot. What EGA card do you have? Was the monitor hooked up to it? What happens if you connect it to the regular 6300 display card?

    I don't have the 1.21 ROM BIOS so I haven't disassembled it to see if/why/how it skips 44h, sorry.

    For the 1.43 board, the very next stop after outputting 45h is initializing the video and printing a message:

    Code:
    seg000:DD55                i_pic_ok:                               ; CODE XREF: seg000:DD1Aj
    seg000:DD55 B0 45                          mov     al, 45h ; 'E'   ; Checkpoint #5
    seg000:DD57 BA 78 03                       mov     dx, 378h
    seg000:DD5A EE                             out     dx, al          ; Printer Data Latch:
    seg000:DD5A                                                        ; send byte to printer
    seg000:DD5B
    seg000:DD5B                i_pic_end:                              ; CODE XREF: seg000:DD4Dj
    seg000:DD5B BC 00 01                       mov     sp, 100h
    seg000:DD5E E8 AE 03                       call    i_vector        ; Install Vector Table
    seg000:DD61 E8 FA 02                       call    i_d_init        ; Determine System Configuration from Switches and Initialize Video.
    seg000:DD64 B4 0F                          mov     ah, 0Fh
    seg000:DD66 CD 10                          int     10h             ; - VIDEO - GET CURRENT VIDEO MODE
    seg000:DD66                                                        ; Return: AH = number of columns on screen
    seg000:DD66                                                        ; AL = current video mode
    seg000:DD66                                                        ; BH = current active display page
    seg000:DD68 32 E4                          xor     ah, ah
    seg000:DD6A CD 10                          int     10h             ; - VIDEO - SET VIDEO MODE
    seg000:DD6A                                                        ; AL = mode
    seg000:DD6C BE CA D9                       mov     si, offset aResidentDiagno ; "Resident Diagnostics\r\nRev 1.43\r\n\n"
    seg000:DD6F E8 88 02                       call    DRomString
    So if it outputs 45h and then you see nothing, it couldn't set the video mode and print the "Resident Diagnostics" message. (That's why I asked you about the EGA card.)
    Offering a bounty for:
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  9. #89
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    Oct 2014
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    Plese note that for add on graphics card the internal graphics card of M24/6300 has to be modified (remove a gal and bridge it). If you plugin a graphics card in M24 with unmodified internal graphics card you damage the machine! If you startup modified M24/6300 without add on graphics card, it won't boot.

    As far as I remember you can find the description how to modify the graphics card on the 6300 shrine website. Trixter, you should have the description from my upload.

  10. #90
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    The 1.43 ROM BIOS kit came with two PALs/GALs, I thought?
    Offering a bounty for:
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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