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Thread: Tandy 1000SL Memory Issues

  1. #1

    Default Tandy 1000SL Memory Issues

    It wasn't clear if this should go here or in the PC/Clones area...

    I have a Tandy 1000SL that I've had for like 10 years. When I first got it, it worked fine. Detected all 640k RAM. About 2 years ago after it sitting on the shelf for a couple years, I turned it on and it would just give me a blinking underscore line cursor in the upper left corner of the screen. I ended up determining that it's some kind of memory issue. There are what I'm going to call 3 banks for the ram chips, 1 with 4 in the bottom left corner of the board and 2 with 8 on the right side of the board near the floppy drives. I admit I'm not the most familiar with how these older boards work, but it looks like you have to fill the entire bank up with chips for it to detect any of them. The right most bank with 8 works fine, as well as the one in the bottom left. With all 12 of those slots filled, I get 384k. When I fill the 2nd bank of 8, it will go back into that blinking cursor thing. I can put memory in half of the 8 slots and it will still boot up, although does not detect the new RAM. However, if I put RAM in ANY of 4 specific slots, it will break.

    I've tried moving memory from the other bank of 8 into this 2nd bank of 8 to see if the slots are bad, but then it throws memory errors. But it will also throw this same error if I pull the RAM out of both of the larger 8 banks. I don't know if it's because that first bank is required to be filled or if it's an issue with the slots.

    I believe I tested all the RAM chips a couple years ago when this first happened, and they all seemed fine. Unfortunately, everything got put on a shelf for a few years, and I moved since, and either threw the 4 "extra" chips out on accident or lost the 4 chips I pulled out. I just ordered 8 more chips last night, but of course, it will be while before they arrive.

    Again, I don't think the chips themselves are bad. So, making this assumption until I figure out otherwise, is there anything I can do to try to figure out why the board does not like this second bank, or perhaps those specific 4 slots? I can't see any physical damage anywhere.

    I purchased a lo-tech 1MB memory expansion card thinking I could use that to make up the difference between 384-640k of ram. It doesn't matter how I configure the ram board, the motherboard seems to override it for the 0-640k range. I was hoping since there are no chips in the 384-640 range, I could use the RAM card. I've even tried to use memory ranges above 640k and use different utilities to remap it into the conventional range, or use as upper memory, but nothing has seemed to do anything. I can see that the motherboard is detecting that there is memory in some of those higher ranges with certain utilities, but nothing seems to let me utilize it.

    90% of the programs I've tried to run to help me troubleshoot this won't run because of insufficient memory. I'd really like to use this computer, but it's almost useless like this, and very frustrating. I'm at the point right now, where if the new ram chips don't help (Which again, I don't think they will because I believe I tested the other chips before they were lost) that I'm considering throwing the motherboard in the oven and see if something needs to be re-flowed, or maybe I need to replace a different chip on the motherboard, but I wouldn't even know where to begin to diagnose it. The only program I can find that actually runs and shows me memory info, is a program called umbinfo that is entirely in German, and that lists the 384-640 range as "Free" which appears to mean there's nothing there, as it appears to normally list available usable areas as "RAM."

    Any suggestions are appreciated.

    Thanks

  2. #2

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    More clarifying info:

    Sorry for not posting pictures originally, I just got everything back in the case, and the area's kind of a mess to get photos of properly.

    I have marked up a photo of the board I found online, and added one of my actu



    To help better explain, in the above image, the pink and blue areas are populating with memory and working normally. All are 64x4 with the -12 at the end. The BLUE is Micron brand, the PINK are Samsung I believe, but both are -12. Although it does not appear to matter if I mix the brands.

    The Micron Branded are: MT4067-12
    Samsung Branded are: KM41464AP-12

    If I populate the Pink and the Blue sections, I get 384k. If I populate the yellow section, the computer will still turn on and boot, but it stays at 384. If I populate ANY part of the red section, the computer no longer boots, I just get a blinking underscore "_" in the upper left corner of the screen.

    So, if I populate the the entire section of RED+YELLOW the computer doesn't work. If I populate just the red, it doesn't work. If I populate the yellow but NOT red, it turns on and boots but does not seem to realize anything is in the yellow section. I assume it needs the entire 8 to be detected to add the RAM, so that part makes sense to me.

    If I remove RAM from all but the PINK section, I get a memory error and it will not boot. Just an error on screen. If I pull ALL RAM, I get crazy corrupted colors/graphics on screen. If I populate PINK plus RED/YELLOW but NOT Blue, I get same memory error as only having pink populated. The error doesn't get me any results online.

    Prior to it getting cranky a couple years ago, all sections were populated and it worked fine. The RED+YELLOW at that time was also Samsung RAM mentioned above. I still have 4 of them, but lost the other 4. As far as I could tell, all 8 from that section were fine. I ordered 8 replacement of the Micron variety yesterday, but it will take a week or two to arrive.

    My fear is that replacing all the RAM in the RED+YELLOW areas will not help, because I am fairly sure I tested all the ram I pulled from those sections by putting it in the blue section without issue. That led me to believe something about the RED+YELLOW sections were bad, be it the bank itself, or a chip that handles them, or something.

    There are no jumpers or config for the RAM from what I can tell. There is 1 jumper on the motherboard, and that designates the onboard Video vs hdd IRQs.

    As for the SETUP program for the bios, unfortunately there's nothing really related to the RAM in there.

    Here is a photo of most of the RAM slots



    It's upside down because of the text orientation, so the left side on this picture is actually the right side of the above picture.

    You can see I have 4 slots filled right now, as it will still boot with those, although it doesn't recognize them.

    If it comes down to it, I might try to put the board in the oven and see if it will reflow and fix any iffy solder, but that's my last ditch step. I've done this before with laptop boards and had success, but don't like doing it, as once you do it, your oven always smells like noxious fumes for a long time after, and I don't want to accidentally make anything worse. I also suck at soldering, I've only attempted it once or twice, and half ruined what I was working on... I was hoping that I could get the 1MB expansion card to work with it to act as a replacement if all else fails, but it seems that the motherboard overrides everything, and there are relatively few memory addresses free outside those ranges. Even the few that are, there doesn't seem to be away to add it to conventional memory that I've seen, or at least one that works.

  3. #3

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    Try going into Genres and then Tandy Radio Shack - the folks there should be able to offer advice.

  4. #4

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    I wasn't sure, the forum descriptions aren't the easiest to follow. The Tandy area makes it sound like it's for just the non-XT variants, so that's why I posted here. Although I see now others have posted some 1000 series things there, I kind of would have assumed since my posts need to be moderated / approved prior to them showing up since I'm new, that it'd get redirected if it was wrong. I can try to repost it there or link to here from there, as long as it doesn't end up getting marked as duplicate or someone gets cranky cause I've double posted the same thing.

  5. #5
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    Default

    Not that it really helps a lot, I'm sure, but if you're wondering why pulling the "pink" area gives you a garbage screen it's the chips in that area that do double-duty as both system RAM and the video RAM. That RAM is slaved to the "Big Blue" gate array chip that drives the video and it's automatically mapped at the end of the base memory segment; IE, if you have 256k installed in the other sockets that RAM moves to fill 256k-384k, if you have 512k in the other sockets it moves up to the 512k-640k slot. It's interesting that you get a halt with no other RAM installed instead of it booting as a 128k machine; an original 1000 would have, but it probably makes some degree of sense that this machine expects at least one expansion bank full.

    Someone who actually owns an SL should be able to tell you if "Blue" sockets are appropriate for the original memory that came in a 384k SL; the "Notes and Jumpers" PDF only says to expand one from 384k to 640k you "fill the empty sockets", it doesn't say which sockets those are. (Likewise the tech manual doesn't say; I could probably suss it out from squinting at the schematic but life is too short today.) Both say it should just automatically recognize if you've populated the sockets, so no help there. If new 4464 DRAMs don't work then you need to start probing and see if you have a bad RAS/CAS or other signal to those sockets.

    For laughs if you still have the Lo-Tech RAM card handy: Try configuring it to supply memory from 256k-512k. Remember that unintuitive thing I said about the Big Blue memory insisting on floating up to the end of the 640k area? Its desire to do that means that if you tried configuring the card to fill the space from 384k-640k like you would in a PC with 384k that's not where the Tandy's going to look for it; it'll stop counting up from 0 the moment it gets a negative result at a 128k boundary, land the Big Blue there, and ignore any RAM that comes later. IF whatever's keeping that bank from working doesn't actively interfere with alternate RAM sitting on the bus AND the Tandy is polite enough to put Big Blue after it then maybe it'll work. I'm not going to put great odds on it though because there might be a buffer or something on the motherboard that's going to come on and trash the overlapping area.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  6. #6

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    Quote Originally Posted by Eudimorphodon View Post
    Not that it really helps a lot, I'm sure, but if you're wondering why pulling the "pink" area gives you a garbage screen it's the chips in that area that do double-duty as both system RAM and the video RAM. That RAM is slaved to the "Big Blue" gate array chip that drives the video and it's automatically mapped at the end of the base memory segment; IE, if you have 256k installed in the other sockets that RAM moves to fill 256k-384k, if you have 512k in the other sockets it moves up to the 512k-640k slot. It's interesting that you get a halt with no other RAM installed instead of it booting as a 128k machine; an original 1000 would have, but it probably makes some degree of sense that this machine expects at least one expansion bank full.

    Someone who actually owns an SL should be able to tell you if "Blue" sockets are appropriate for the original memory that came in a 384k SL; the "Notes and Jumpers" PDF only says to expand one from 384k to 640k you "fill the empty sockets", it doesn't say which sockets those are. (Likewise the tech manual doesn't say; I could probably suss it out from squinting at the schematic but life is too short today.) Both say it should just automatically recognize if you've populated the sockets, so no help there. If new 4464 DRAMs don't work then you need to start probing and see if you have a bad RAS/CAS or other signal to those sockets.

    For laughs if you still have the Lo-Tech RAM card handy: Try configuring it to supply memory from 256k-512k. Remember that unintuitive thing I said about the Big Blue memory insisting on floating up to the end of the 640k area? Its desire to do that means that if you tried configuring the card to fill the space from 384k-640k like you would in a PC with 384k that's not where the Tandy's going to look for it; it'll stop counting up from 0 the moment it gets a negative result at a 128k boundary, land the Big Blue there, and ignore any RAM that comes later. IF whatever's keeping that bank from working doesn't actively interfere with alternate RAM sitting on the bus AND the Tandy is polite enough to put Big Blue after it then maybe it'll work. I'm not going to put great odds on it though because there might be a buffer or something on the motherboard that's going to come on and trash the overlapping area.
    I noticed yesterday when I had just the 4 in the "pink" section populated but nothing else, the memory address error it was trying to read was 0000h and the address it was trying to write I believe was the memory address that corresponds to the onboard video. It I put in an EGA ISA card in place of the onboard, it will just instead give nothing on the screen instead of that error when it doesn't have the other bank filled.

    I just tried what you suggested, and enabled it for 256-512, no noticeable change, still shows 384. Thanks for the suggestion though. The closest I've had it to seeing more RAM was once or twice with a program I found that I believe someone specifically wrote for a Tandy machine, it is supposed to let you remap memory outside of lower conventional ram into the conventional ram. With how many other onboard devices this machine has, there's only a small section here and there above 640k that it seems to recognize the 1MB RAM board on, and it's like 32 or 64k or so, and most of the time it won't let me remap it. Sometimes it seems to act like it did, and will show more free conventional on the mem command in dos, but then it will do something buggy and stop working or won't let me run the same exact command to remap the same addresses next time. I can see more usable upper addresses on my Commodore machine, but it has 640k already, and they're not removable, so I can't remove any to test if the remapping could theoretically work or if it would work with the card to take over the unpopulated area of conventional ram if it didn't have it filled already.

  7. #7

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    I recieved the 8 pieces of RAM I bought, half appear to be from one batch, and the other half from a different, I'm assuming the 4 digit numbers on the chip are date codes, one starts with 87, one starts with 89. The 87 ones have slightly shorter pins, and I cannot get any of those to be recognized.

    Luckily, I was only short 4 pieces, so I can fill in all 20 spots now, and I've moved every piece around between multiple different slots, and as far as I can tell, all 20 that are in the machine are good, however, it still does not recognize the 2nd bank of RAM from 384 to 640. The only difference, is now instead of just flashing a underscore cursor at the top left when you turn it on if any chips are in that one section of 4, now it will actually post if you leave the machine off for a minute or two or more, but only show the 384k still. If you reboot after that one time, or turn off and back on within a very short time, it will do that underscore blinking cursor.

    I don't know enough about how these work to troubleshoot any further unfortunately. I've tried pulling all chips one by one that are removable to see if any different is made. I've tested the resistors that I believe are for the memory, and all appear to have the correct readings. All solder joins look fine, I've tested continuity between the top of the board where the removable ram goes and the bottom.

  8. #8

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    Hello I am wondering how you are fairing against the memory issue with your 1000SL? I am currently working on one I bought from a family member.
    I was getting this screen
    coqzv4b0we251.jpg

    After swapping some of the ram around and reseating the display now shows this
    IMG_3707 (2)-min.jpg

    I am amazed at how little documentation there is for these computers online. I guess the SL wasn't that popular or something?

  9. #9

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    Hey, sorry for the delay in response, I haven't been checking this as much since I wasn't getting any responses for a while.

    Personally, I haven't gotten any farther with my issue. There is likely something wrong on the actual motherboard with mine, assuming either a chip somewhere, a resistor, or a bad connection or trace. I don't know enough about the separate components of these to troubleshoot much further, unfortunately. I've been testing pieces here and there as I come up with ideas. But, I haven't found anything wrong yet. I've checked voltages, swapped ram around, replaced ram with different chips, etc, everything appears fine until you put something in the 2nd memory bank, mostly the one portion of it. My next step as of right now is to either just randomly try testing things as I come up with ideas or putting it back together and leaving it with the max amount of RAM it will successfully work with (384k) and trying to sell it with the idea that someone might have a use for it even with that bottleneck. I unfortunately don't, as anything I would use it for needs more than 384k. I'm also going to try to reach out to the manufacturer of the ISA ram card I bought to see if they can provide any insight on if there's any possibility to get the cards RAM to over ride the motherboard in the 384-640k range. I'm doubting there is without some physical changes to the board that I'm not qualified to be able to figure out... If I end up not being able to use it, I may look for a different machine to replace it.

    As for your issue, you do have one thing going for you, it does detect the 640k in the 2nd and 3rd pictures. Mine doesn't even get that far. I'm guessing you probably just have some bad ram chip(s) somewhere. My vague understanding is that the base 2000 and 3000 it is complaining about is the range from 128k-192k and 192k-256k. The 128k-384k memory ranges I believe are in the section above I enclosed in blue in an earlier post above. I have seen errors like these with mine, and sometimes just shuffling or reseating the chips takes care of it. If that doesn't, I would remove all the chips from the red and yellow areas in the image I posted above. That is the 384-640k range, which the computer can boot without. See if it errors then. If it detects 384k ram and has no memory errors, the bad chips may be in the ones you just removed. If it goes down to 384k and still complains about those memory errors, try removing all the chips in the blue bank and inserting the ones you pulled from elsewhere, still leaving the 384-640k range empty. If it then boots without issue, you probably have a bad chip or two. In which case, you will want to start swapping the memory chips in the blue area one by one and booting the computer until it starts erroring. Hopefully that way, you will find which chip is bad, if any. Once you find the bad chip, you can order a replacement.

    Also, make sure the chips are all facing the correct direction, and all sections need to have a chip for that section to work. The only section based on the image above that mine will boot without is the red/yellow section. The other sections appear to be required.

    Hopefully that helps.

  10. #10

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    I got mine working by swapping chips one by one until it functioned with 384k. Once I got it booting I swapped out all the MT 4067s on the board for the chips from the 256K upgrade my father added years before They were LH2464s. In my experience MT branded chips don't hold up well. They were made to a price and suffered for it. Jameco still sells NEC 41464-10s for about 2.50 a chip, Chuck(G) helped me out in a WTB post I made. I would of never thought to search a modern parts supplier for them! If you do decide to replace the memory with the parts from Jameco and that doesn't work. I'd check if there is significant drop on the PSU or any bad traces or caps. The SL appears to have a two sided board so tracing the connections shouldn't be too difficult.
    Check out my collection and what I'm working on @ simplyvintagepcs.blogspot.com

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