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Original-IBM-5150 or IBM-Clone Memory Experimentation Thread

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  • T-Squared
    replied
    Originally posted by modem7 View Post
    Be wary of the Supersoft/Landmark diagnostic ROM. It is not comprehensive. I doubt that its RAM test is looking for addressing issues.

    And the address of 05040 is a known red herring. Example at [here].
    Would this be a better diagnostic to use, then? https://www.vcfed.org/forum/forum/ge...d-compatibles=

    (EDIT: Never mind, it doesn't seem to be hosted anymore...)
    Last edited by T-Squared; April 20, 2021, 08:57 PM.

    Leave a comment:


  • modem7
    replied
    Originally posted by T-Squared View Post
    I'm still having problems, and the reason why I said it was weird is because I took bank-after-bank of memory out to make sure the Supersoft diagnostic would detect that some of it was missing, but it's now reporting the wrong kind of error, which is what it did before: a memory failure at address 05040, with the same failing bits in memory (7,6,1, 0, or so), even though none exists on the board now.
    Be wary of the Supersoft/Landmark diagnostic ROM. It is not comprehensive. I doubt that its RAM test is looking for addressing issues.

    And the address of 05040 is a known red herring. Example at [here].

    Leave a comment:


  • T-Squared
    replied
    Okay, last post of today. I'm looking at other clone systems that used 640k of RAM to see if I have my ideas straight, and if there are similarities between them and the Sanyo.

    Namely, I'm using this schematic from a Turbo XT computer: http://minuszerodegrees.net/manuals/...on%20Guide.pdf

    So far, I've seen a lot of similarities. They both use 373s, 244s, and 245s in-line with the memory, for a start. However, they all use similar composite color output circuitry, too (Both with a "color adjust" variable capacitor, for one.)

    Leave a comment:


  • T-Squared
    replied


    Here's a full run-through of one pass of diagnostics, just to show the problems.

    Leave a comment:


  • T-Squared
    replied
    I thought I had something, but it's turned weird now.

    I've heard of a jumper being added to a location on the normal 5160 board to get 640k to work, and the only other jumper available that was near the memory logic was a unpopulated one. (and it seemed suspicious because there was a resistor connected to one via of the through-hole pair, with another resistor behind it and a trace snaking off somewhere on the board.) So I added a pin header and a jumper to it.

    I'm still having problems, and the reason why I said it was weird is because I took bank-after-bank of memory out to make sure the Supersoft diagnostic would detect that some of it was missing, but it's now reporting the wrong kind of error, which is what it did before: a memory failure at address 05040, with the same failing bits in memory (7,6,1, 0, or so), even though none exists on the board now.
    Last edited by T-Squared; April 19, 2021, 06:07 PM.

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  • T-Squared
    replied
    Been a while. I'm still trying to figure out this stuff, but I think I've found analogous chips between the 5160 schematic and the Sanyo. And as expected and what has been said before, there is one 5160 chip on the schematic that does not exist on the Sanyo, replaced by the mess of logic chips, that performs the same functions, that I'm trying to organize.

    I've been routing logic lines all week, looking for similarities as well, between the Sanyo and schematic.

    The one thing I'm having problems with is trying to route the RAM Address select line on the Sanyo map I've drawn up, so I can figure out where the logical clone of this "decoder" chip starts. (as I inaccurately called it earlier.)

    Leave a comment:


  • T-Squared
    replied
    I've forgotten... I'm actually getting the same consistent bit pattern errors across at least the first 256K of the upgraded RAM, and it's always in consistent address increments.
    e.g. 2000h, 4000h, C000h, 12000h, 14000h... (Yes, I know that this is not correctly incremented. I'm trying to prove a quick point.)

    Leave a comment:


  • T-Squared
    replied
    Yeah, this is weird. It's as if the problem with my computer is not how the memory is connected, but failing chips (Some of which I did get from China). It is reporting errors on memory banks, but not all of them. Some seem to actually be succeeding!

    Would a real IBM not run if any memory chips in the 16K area were faulty?
    Last edited by T-Squared; January 14, 2021, 12:59 PM.

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  • T-Squared
    replied
    Sorry about the long wait. I had to wait for my diagnostic card to get in. I discovered something extremely odd. NOW the entire Supersoft Diagnostic runs, and it MAY be reading memory (not completely) somehow.

    Anyways, I took out the two cards I had installed in the machine (A Western Digital 8/16 Ethernet Card and an XT-IDE CF card), and plugged in the diagnostics card. To my surprise, there was nothing frozen on the card's seven-segment LEDs. Even more strange, the screen now works properly, and it runs through the tests as normal. (Previously, with the diagnostic ROM, the picture would be unstable and roll, and it would stop at the Timer 1 test.)

    I wonder if the previous cards had anything to do with it...
    Attached Files

    Leave a comment:


  • T-Squared
    replied
    Ok, further investigation shows that the memory refresh is not occurring, due to Timer 1 not operating. I'll check it tomorrow and see if there's a wire that needs to be connected to the memory from there.

    Leave a comment:


  • T-Squared
    replied
    Been a while. I got some UV EPROMS and burned a copy of the Supersoft Diagnostics. The diagnostic gets stuck at the 8253 Timer 1 check.

    I get One Hi-Lo and 8 beeps. It suggests the 16k critical memory area is not working.
    (Unless I'm misinterpreting, and the Hi-Lo means two beeps, in which case it says the numeric co-processor isn't working, but it seemed to work when I used the Landmark Diags about a month or two ago)
    Last edited by T-Squared; December 4, 2020, 06:09 PM.

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  • T-Squared
    replied
    A bit of an update: looking at the schematics, this Sanyo is looking more and more like a 5160 clone. The components are all matching up in number and type to the schematics so far. I just need to find out what components are not connected properly.

    Leave a comment:


  • T-Squared
    replied
    A bit of progress today. I got my 64-kilobit chips in today, and I now have a full 640k of memory, which matches the amount in the 5160 schematics.
    I'm still mapping out connections, but it's slow because emotionally, I'm spent because of this quarantine.

    I'm betting that the logic connections don't match exactly with the IBM schematics; maybe what is the difference is that the connections are logically the same (same type of input pins, same type of output pins), but connected to different pin numbers because of routing differences in manufacturing?
    CuriousMarc did the same thing when performing repairs on a Xerox Alto. One logic gate within an IC was bad, so what he did was rerouted those signals to an unused gate of the same type on the other side of the chip, which allowed them to temporarily make progress until they could source a new modern-built version of the chip.

    Leave a comment:


  • T-Squared
    replied
    This mapping is already getting complex, but I'd like to see what I can do.

    I have noticed patterns that are cropping up:

    The 158s are all at least connected to an input (on one chip) AND an output (on another), forming a complex series of logic valves.
    Control pins (that control the impedence / basic on-off state) are all connected to GND.


    The good thing is that the RAS and CAS are indeed connected to 138s. Now I just need to figure out where those 138s figure into the picture.
    Last edited by T-Squared; November 5, 2020, 09:28 AM.

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  • T-Squared
    replied
    Thank you. I'm sorry if I don't sound like I'm up to the task.
    There's a lot of jargon to sift through too, and I don't always get them right (despite my knowledge) and things lately haven't exactly been spring chicken.
    I do understand that there are lines that go from the CPU to memory. (Maybe not directly. Again, though, I tend to get them mixed up.)

    However, I've seen videos about how memory (Doom's cheat codes), and read about how disk contents [Apple II Disk II writing-to-disk methods], can be obfuscated, so I assumed that there was some shuffling/scrambling of groups of bits here and there to re-create the proper data grouping for the CPU to understand.

    The tracing of the pathways makes a bit more sense now.

    G, on [Sanyo] U45 and U47 is indeed attached to ground.

    Right now I'm reworking my pathway tracing to make it easier to read and organize. I'll see if I can look a bit more into the logic of the chips.
    Last edited by T-Squared; November 2, 2020, 08:58 PM.

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