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Motherboard debugger

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  • Chuck(G)
    replied
    Maybe, but I don't particularly care for those people's technique of mangling a keyboard to work with a PC by making it not work with the original equipment.

    Leave a comment:


  • Samir
    replied
    I've always found that no project goes wasted--it just needs to find the audience. I bet the keyboard communities would appreciate this effort even if they don't use it for that particular IBM keyboard.

    Leave a comment:


  • Chuck(G)
    replied
    I can't answer that last one--I've certainly posted several times here on the subject--and there are various postings on the web for people trying to figure these things out. The keyboards, while rubber-dome are definitely a notch above the usual garbage--and they're new IBM stock, though made in China.

    I picked one up originally because (a) it was too-temptingly priced and (b) I was looking for a reasonably-priced "space saver" keyboard. I got what I wanted, and mistakenly thought that others might be interested. With a little tinkering with the firmware (the decoding is already done), it could be converted into, say, an alternative to the PCJr "chiclet" keyboard or the like.

    I currently own 4 of the things.

    Leave a comment:


  • charnitz
    replied
    Originally posted by Chuck(G) View Post
    The prime issue to me is "will this see an audience to make it worth the effort?"

    Last year (?), I uploaded some code for a Blue Pill to transform the cheap IBM-branded IR keyboards into a PS/2 interface unit. (As of yesterday, you could pick one up from Goldmine Electronics for $3.95). I said to myself "surely, there will be someone out there excited to try this out on their legacy systems". Nothing, no issues, bupkus. Was it worth the effort to develop? Sure--I use the things routinely. Was it worth the effort to document and post to github? Probably not.
    Isn't it practically the definition of vintage that the audience is niche and the audience for a specific application to a specific product is a niche of a niche? Also, is a year sufficient to see if someone someday finds it useful? It could be that the answer to "is there an audience to make it worth the effort?" is always no when it comes to vintage stuff, even "popular" vintage stuff, but don't we all find, from time to time, that piece of information someone preserved for no discernible reason that is actually quite useful for us at that time, even if it is a report that the path was tried and found to lead into the bramble patch?

    Also, for the IR to PS/2 project, is that a problem that people have for which that would even occur to them as a potential solution? Is the lack of interest from discoverability of possibility, not applicability?

    Leave a comment:


  • Chuck(G)
    replied
    The prime issue to me is "will this see an audience to make it worth the effort?"

    Last year (?), I uploaded some code for a Blue Pill to transform the cheap IBM-branded IR keyboards into a PS/2 interface unit. (As of yesterday, you could pick one up from Goldmine Electronics for $3.95). I said to myself "surely, there will be someone out there excited to try this out on their legacy systems". Nothing, no issues, bupkus. Was it worth the effort to develop? Sure--I use the things routinely. Was it worth the effort to document and post to github? Probably not.

    Leave a comment:


  • charnitz
    replied
    While the consensus of Those Who Know Things seems to be that this would be a difficult or impossible task, which seems a reasonable prognostication, what's the harm in trying it? It seems like it would either quickly show its true teeth or turn into something interesting. Why don't you just start it and write detailed, regular updates of what you are encountering?

    Is there some motherboard that could be easily purchased for cheap in quantity on eBay that other people on the forum could acquire to test your kit? Something where introducing issues to then test wouldn't destroy anything important and, ideally, be reversible?

    Leave a comment:


  • MicroCoreLabs
    replied
    An option could be to use my EPROM Emulator: https://microcorelabs.wordpress.com/...prom-emulator/

    It is basically a 600Mhz CPU which emulates an EPROM, so it could be programmed to trigger/trap/store the BIOS progress and report back to the user's console via the USB-UART.

    Leave a comment:


  • kdr
    replied
    I've had a somewhat more modest goal in mind for a while now:

    Write (or modify) a PC/XT BIOS that tries really really hard to provide feedback about what it's doing during POST.

    So that probably would mean twiddling the speaker outputs on the 8255 PPI as the very first step (using a tight software loop instead of programming the 8253 timer) followed by a series of speaker 'clicks' during the memory test (similar to what some 386/486 era BIOS would do). Followed by the standard repertoire of POST checks, but sounding a beep code prior to halting the CPU when a test fails.

    Regardless, a totally dead motherboard is very tricky to debug no matter how it's approached.

    Leave a comment:


  • MicroCoreLabs
    replied
    Originally posted by Chuck(G) View Post
    Given the amount of work that you're going to have to put into this thing, what do you anticipate that the demand will be? It seems to me that the skilled people would rather resort to the test equipment on their bench. There can't be that many tyros interested in repairing vintage (pre 80286) systems, can there?
    Thats why I asked.

    We're on page-3 of this thread with a couple hundred views without any interest expressed, so it appears I should look for another project!

    Leave a comment:


  • Chuck(G)
    replied
    Given the amount of work that you're going to have to put into this thing, what do you anticipate that the demand will be? It seems to me that the skilled people would rather resort to the test equipment on their bench. There can't be that many tyros interested in repairing vintage (pre 80286) systems, can there?

    Leave a comment:


  • MicroCoreLabs
    replied
    Originally posted by modem7 View Post
    I agree. With a scope of all chips (and all traces), I see a vast amount of 'diagnostic tree' logic, even for something simple like the IBM PC motherboard.
    Noted.


    Originally posted by modem7 View Post
    See the diagram at [here], in particular, the faulty OR gate at top left. The gate's output is alternating. With my multi-channel oscilloscope (or logic analyser), I can simultaneously monitor the gate's three pins and from that, deduce that the gate is faulty. A single probe will not be enough to inform me that the subject gate is faulty.
    In my case, the source of your gate would be driven to a known state by my hardware, so only a single probe would be needed at its output. Note that I have control over the bus and can probe with 20ns granularity throughout the cycle, so I should be able to set gate inputs and observe their outputs within bus cycles. I will probably need two probes though to check for delay-line or clock to out timing in some cases.

    Leave a comment:


  • MicroCoreLabs
    replied
    Originally posted by modem7 View Post
    Enough interest to purchase a ready-to-use product (i.e. you do all development work), or enough interest from people who will be willing to customise the software for particular boards ?
    It would be open source, so both are options. Once the hardware and first version of debug software works then others could adapt it to additional motherboards

    Leave a comment:


  • modem7
    replied
    Originally posted by Chuck(G) View Post
    I think the task is more than anyone expects.
    I agree. With a scope of all chips (and all traces), I see a vast amount of 'diagnostic tree' logic, even for something simple like the IBM PC motherboard.

    Originally posted by MicroCoreLabs View Post
    Basically, if you can debug the issue with an oscilloscope, then this system should also be able to detect it.
    See the diagram at [here], in particular, the faulty OR gate at top left. The gate's output is alternating. With my multi-channel oscilloscope (or logic analyser), I can simultaneously monitor the gate's three pins and from that, deduce that the gate is faulty. A single probe will not be enough to inform me that the subject gate is faulty.

    Leave a comment:


  • modem7
    replied
    Originally posted by MicroCoreLabs View Post
    It could be extended to support any type of processor or motherboard, but for now I am investigating whether there is enough interest to invest time in the project...
    Enough interest to purchase a ready-to-use product (i.e. you do all development work), or enough interest from people who will be willing to customise the software for particular boards ?

    Leave a comment:


  • the3dfxdude
    replied
    Originally posted by MicroCoreLabs View Post
    It could be extended to support any type of processor or motherboard, but for now I am investigating whether there is enough interest to invest time in the project...

    I have been watching a number of YouTube debug videos recently where the host has access to a debug ROM, an oscilloscope, and the schematics but still ends up desoldering/replacing multiple chips until they stumble on the broken one.
    It sounds like you watched this video: https://www.youtube.com/watch?v=SQHt5Ccvn3M

    These hosts have debugging skills and equipment greater than the average vintage hardware enthusiast yet they still struggle finding the faulty IC's. The enthusiast is even less likely to achieve success...
    I think knowledge and experience on understanding circuits and using instruments probably has more to it. Not sure if an all in one debugger can allow an enthusist's entry. If so, I better look for a new job. However, I welcome more tools for myself! If they can complement standard equipment well.

    Leave a comment:

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