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IBM 5170 Extended Memory Card Mystery

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    IBM 5170 Extended Memory Card Mystery

    I just had the sudden urge to revisit a mystery that has left me... well, mystified, since the early 2000's!

    I was just really getting into computers around this time and had a bunch of old systems that I was tinkering with, many of which I still own, and one of which is a blinged-out PC-AT: EGA monitor with stand, 84-key keyboard, 30MB hard disk, co-processor and AutoCAD with the tablet! I would have had a plotter with it too, but I simply didn't have the room to store that beast - it was huge!

    It came with an IBM extended memory card that has two serial ports and a total of 12 30-pin SIMM sockets, two of which are populated with 1MB SIMM's giving a total of 2MB of extended memory. And the mystery is I've never been able to add more than 2MB of memory onto this card, and couldn't figure out why.

    It has a row of 8 DIP switches, and leaving it in the configuration I originally found it in leaves me with 2MB visible by the system. Adding SIMMs will still only leave 2MB seen by the system; changing the DIP's randomly will stop that system from seeing that 2MB. The serial ports have never worked for me, leaving me to use another serial card to use the mouse.

    Obviously the key to my mystery is the DIP switch settings, but I've never been able to find a manual or any online info for this card as to what settings will enable the use of more memory. I have deduced that the card needs 9-chip parity SIMMs, as that's what was installed on them originally; using 3-chip or 8-chip SIMMs in place of the originals will not work. I have tried other 9-chip SIMMs in place of the originals and they WILL be seen by the system.

    It is a full-length 16-bit ISA card. It has a male DE-9 and a female DB-25 serial port. One bank of SIMM slots is labelled 'high byte", the other "low byte". The DIP switch is labelled 'S1' and has switches 4, 6 and 7 turned on; the rest are off.. The card is labelled in the upper left-hand corner "ASM 55X3543" and "EC A25158[4287]". A prominent metal-covered circuit is labelled "65X5770ESD / IBM 14".

    My goal is to fully populate this card with as much memory as it can hold (12MB?) as well as getting both serial ports functional, so I can remove the other serial card.

    I can provide an image of this card if it is requested. Any help given would be most appreciative.

    Please provide a picture. I haven't seen an IBM memory card for the AT that used SIMMs. Seen plenty from other companies of course.

    Do you have an EMS driver? If the extra memory isn't showing as extended, I would suspect the card is listing the memory as expanded. Just a guess though. Would need to identify the card to discover what setup disk goes with it to be able to tweak the memory correctly.


      Maybe this one?


        I have the same card with 4 SIMMS. These are the very old SIMM style with the 'can' chips...I think these are 256K or 512K SIMMS on my card.
        I think this card is documented in the IBM 5170 Options & Adapters.
        Attached Files
        Last edited by mikey99; March 13, 2016, 10:16 AM.


          That's the card, mikey99!

          And thanks for the off-site link, gslick! That seems to be my card with the one exception of my DIP switch having 8 settings instead of the 7 indicated on the documentation. Could the 8th switch simply not be used?

          I'm going to try messing around with it shortly. I have the original DIP switch settings saved, incase I have to revert.


            For those who did not read the second link within post #3, note that there is high probability that this card is the "PS/2 Multifunction Adapter", a card optionally supplied with the PS/2 Model 30 286.


              Heh, believe it or not the original author of that thread from 2003 was... me! And although I managed to get the card working with the 2MB of SIMMS that came with it, I never got it to function with more memory than that, nor did I ever get the serial ports working properly.

              I'm actually starting to think the card may be damaged, as I have just tried toggling through the first five DIP switches in a progressive binary-like format and I got very confusing results. Firstly, it does NOT follow the settings as described here - at all. Despite the layout similarity, it is completely off base in operational settings.

              With all five DIP switches either OFF or ON, the system will not boot; having only the fifth switch on will also cause a no boot scenario. Only with the fourth DIP on in will it read 2048KB of extended memory; adding additional memory with this setting will not allow any beyond 2048K to be seen by the BIOS upon startup. All other combination of switch settings would only cause the system BIOS to read the 640KB of base memory and nothing else, with the sole exception of switch combo 2, 3 and 5 ON which caused the system to only see 512KB of base memory.

              Any amount of SIMMS installed beyond 2MB will not be seen by the system. I made certain I was using matched pairs of 9x1M chip SIMMs per bank. Alternating these pairs with the original pair found on the memory card will not alter the results I've had thus far.

              I happen to have another generic 16-bit ISA extended memory bank card that takes 30-pin SIMMS to a maximum of 8MB, and installing this fully populated into my 5170 will cause all 8MB to be seen by the BIOS upon startup, so this tells me this is not a limitation of the system BIOS preventing me from using vast quantities (for the system architecture) of extended memory.

              I suppose I shall give up for now. I may go through the entire 8 switches in a continuing fashion as to what I've been doing, but not tonight. Thanks for the replies so far!


                Originally posted by ArchieX View Post
                Any amount of SIMMS installed beyond 2MB will not be seen by the system. I made certain I was using matched pairs of 9x1M chip SIMMs per bank. Alternating these pairs with the original pair found on the memory card will not alter the results I've had thus far.
                If this card is the "PS/2 Multifunction Adapter", then IBM-proprietary SIMMs are required.
                The logic behind that is the combination of:

                1. According to the thread at [here], the motherboard (planer) of the PS/2 model 30 286 uses IBM-proprietary SIMMs.

                2. In the document at [here]:
                * The "PS/2 Multifunction Adapter" is also referred to as feature #8635
                * Contains in Table 2-D (PS/2 Models 30 286-E01/-E21), "Modules for planar or #8635"
                * Contains, "The PS/2 Multifunction Adapter, Feature #8635 ... Additional memory modules may be moved from the system board to the PS/2 Multifunction Adapter."


                  Looking at the switches appear to be set at :

                  1,2,3,5,7,8 on
                  4,6 off

                  Not sure exactly where my card is right now , I do still have it but could take awhile to find
                  And I'm sure the card works the last time I tried it...I recall the memory counting up to over 2MB.
                  Attached Files
                  Last edited by mikey99; March 13, 2016, 05:29 PM.


                    Decided to futz around with it a bit more before calling it quits for the night, and I have to revise some of my earlier statements, which were based on previous experience and my memory (no pun intended) is being called into question...

                    Using other SIMMs in the place of the pair that came with the card will NOT work; only the pair of 9-chip Hitachi HM511000AJP12 SIMMs will work in this IBM expansion card.

                    The Boca Research memory card I have WILL work in the system... but ONLY with the above mentioned SIMMs, the Hitachi HM511000AJP12; any other 9-chip 1MB sticks in my possession will NOT work in my PC-AT 5170, regardless of the expansion card used.

                    So my problem is not with the card itself, but with the type of memory I'm using; apparently my 5170 is rather picky in such regards. But I can't seem to find anything special about this Hitachi memory when compared to my other available sticks (Mitsubishi 'm5m41002bj' and Fujitsu '81c1000a-60'). All are described as "fast page DRAM" and have very similar timing speeds and specs. They're all 9-chip which means they're parity (right?).

                    But without access to other SIMM's, this also means my efforts to expand the memory in this dinosaur have come to an end. I have some 4MB SIMMs and a plethora of 256 and 512K, but am quite certain they won't work.

                    This has me scratching my head. Any input in regards to this?


                      ... wait. I thought having the red portion of the switch up near the 'off' edge of the switch meant it was off.

                      In that case, my methodology was entirely backwards. That means the switch settings of my functioning card would be 1, 2, 3, 5, and 8 on; 4, 6 and 7 off.

                      This actually means - atleast for the base memory settings, switch 6 and 7 - that the settings in the link provided above are actually correct for my system: 6 and 7 off for 640KB base memory. But for my extended memory of 2MB, the only switch setting that works is the one indicated for 14.5MB.

                      Again, scratching my head. Certainly doesn't make things clearer for me, hehe.


                        Hmm, that picture is kind of blurry If your card is working with those settings you mentioned in the original post..... then I guess
                        mine are actually the opposite of what I said earlier.


                          Originally posted by modem7 View Post
                          For those who did not read the second link within post #3, note that there is high probability that this card is the "PS/2 Multifunction Adapter", a card optionally supplied with the PS/2 Model 30 286.
                          I am thinking that it is this:


                            Originally posted by yuhong View Post
                            Congratulations. I think you have nailed the card's identity (the "Memory Expansion Adapter").


                              Hmm. I also just found this link which also refers to a "Memory Expansion Adapter" that sounds like my card, and mentions the fact that you would need five of these cards to reach a maximum of 15MB. Meaning that it sounds like a maximum of 3MB is the limit of what these expansion cards can handle.

                              I think I'm starting to see a picture here. This card should be populated with 9-chip 256KB modules to give me 3MB, whereas for some reason I have a lucky set of 1MB modules that happen to work to give me 2MB; my other 1MB modules will not be seen by the system regardless of which memory adapter I use.

                              I'm using the wrong memory and I have an unrealistic expectation of how much memory I can install into this PC-AT. I have boxes and boxes of 256MB SIMMs but none are 9-chip. I might try a few of them later tonight after work just to see if they might work, for curiosity's sake. If they do, I'll be able to potentially increase my expanded memory to 3MB.

                              Thanks for all the help so far, folks. I feel close to finally solving this 13 year mystery!
                              Last edited by ArchieX; March 14, 2016, 02:16 AM. Reason: forgot link