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IBM EGA Card Memory Expansion Boards

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    #31
    Originally posted by maxtherabbit View Post
    In preparation for this, I pulled out my IBM EGA and stuck it in my 5150. It works, but checkit is showing memory errors between 0A0000h and 0A001Eh. There appear to only be 8 memory ICs on the EGA, but I don't recognize the part numbers. Also do not know which one would correspond to this range. I've attached a photo. Any thoughts?
    See [here].

    Comment


      #32
      Originally posted by maxtherabbit View Post
      There appear to only be 8 memory ICs on the EGA, but I don't recognize the part numbers.
      [ATTACH=CONFIG]59465[/ATTACH]
      inmos databook 1986

      www.bitsavers.org/components/inmos/Inmos_Data_Book_1986.pdf

      Page 2-15 (Page 82 of the PDF)
      IMS2620 High Performance 16Kx4 Dynamic RAM
      DESCRIPTION
      The IMS2620 16K x 4 bit dynamic RAM is fabricated
      with INMOS' advanced Double Poly N-MOS technology
      and utilizes advanced circuit techniqes to achieve high
      performance, low power and wide operating margins.
      Multiplexed addressing and common data I/O allow the
      IMS2620 to be packaged in an 18-pin, 300-mil wide
      plastic DIP with JEDEC standard Pinout.

      Comment


        #33
        Originally posted by modem7 View Post
        See [here].
        I'll be damned! So there is no problem at all, good thing I didn't break out the desoldering gun yet.

        Comment


          #34
          Originally posted by gslick View Post
          inmos databook 1986

          www.bitsavers.org/components/inmos/Inmos_Data_Book_1986.pdf

          Page 2-15 (Page 82 of the PDF)
          IMS2620 High Performance 16Kx4 Dynamic RAM
          DESCRIPTION
          The IMS2620 16K x 4 bit dynamic RAM is fabricated
          with INMOS' advanced Double Poly N-MOS technology
          and utilizes advanced circuit techniqes to achieve high
          performance, low power and wide operating margins.
          Multiplexed addressing and common data I/O allow the
          IMS2620 to be packaged in an 18-pin, 300-mil wide
          plastic DIP with JEDEC standard Pinout.
          Excellent, thanks. Good to know they are JEDEC standard 16kx4 DRAMs in case I ever do have an issue with one

          Comment


            #35
            Originally posted by maxtherabbit View Post
            I'll be damned! So there is no problem at all, good thing I didn't break out the desoldering gun yet.
            And CheckIt is reported to do something similar for the IBM PS/2 Display Adapter when a monochrome VGA monitor is connected.

            Originally posted by maxtherabbit View Post
            Excellent, thanks. Good to know they are JEDEC standard 16kx4 DRAMs in case I ever do have an issue with one
            Some compatible chips shown at the bottom of [here].

            Comment


              #36
              Yeah I already tagged that eBay listing for 40x MB81416s that you linked earlier in the thread. I'll have plenty of spares after building the expansion card

              Comment


                #37
                I ended up ordering this pin header for the project
                https://www.digikey.com/product-deta...SAM1058-32-ND/

                According to my measurements, it should be almost perfect and better yet it's a stock item at digikey

                Comment


                  #38
                  For the memory chips, the best deal I found were these

                  Comment


                    #39
                    IBM EGA + Memory Expansion Boards

                    https://www.ebay.com/itm/184209901469

                    Comment


                      #40
                      Originally posted by maxtherabbit View Post
                      I ended up ordering this pin header for the project
                      https://www.digikey.com/product-deta...SAM1058-32-ND/

                      According to my measurements, it should be almost perfect and better yet it's a stock item at digikey
                      I can now confirm this header fits perfectly in real life. Mouser also stocks it, ignore their incorrect description and just trust the part number.

                      Comment


                        #41
                        20200321_155517.jpg20200321_155554.jpg20200321_155903.jpg20200321_162218.jpg


                        thanks to ab0tj for a great design! I went off reservation with my standoffs, just used some crap I had lying around so I didn't have to drill out the expansion PCB

                        notice how the expansion board has a tiny amount of bowing? might want to pull the standoff holes away from the pin header by just a fuzz, like a couple thou

                        Comment


                          #42
                          Awesome! I'm glad to see it worked for you. I think I might need to rebuild mine but with the same header you used. Yours has much better fitment than mine.

                          Comment


                            #43
                            I built one of these a few weeks ago. Worked perfectly first try!

                            The mounting holes are just a hair off, but my mounting screws still make it. I didn't make any adjustment to the layout. I don't have a bend issue with all the dram's sitting flush. The mounting holes are only a minor issue, so the board is perfectly usable, and I have extras here.
                            Attached Files

                            Comment


                              #44
                              I managed to get an original NOS EGA expansion card from a friendly chap who had scored some from Computer Reset. Thought I might chime in to help with whatever info I can add.

                              The male pin headers are approximately 0.4" / 1cm tall, from the PCB surface to the tip of the pins. That's about 0.3" / 8mm of actual mating surface, with the height of the plastic shroud consuming the ~0.1" remainder. It's a 64-pin header in 2x32 arrangement. When you're looking at the component side of the card, with the header along the right edge of the card, pin 1 is the top right corner. Odd pins on the right side, even pins on the left.

                              FWIW, my expansion card came with a plastic guide installed over the pin header. It looked, at first, like a female-to-female coupler, but there are no contacts in it -- just plastic. Might just be there to protect the pins from getting bent in shipping. (Nice touch!)

                              The standoffs have a 1/2" board-to-board spacing. That is, if you snapped the expansion card on to the EGA card, it would be 1/2" between the PCB surfaces. The expansion card holes are roughly 4.65mm in diameter, give or take a bit due to measurement error. My calipers say the neck of the standoff (where it rests in the PCB when installed) is about 3.6mm. NOTE: The EGA card side of the standoff is smaller in diameter.

                              Best I can tell, the standoff holes are 3.5" C-to-C on the left side of the board, and it looks like 5.6" from the standoff center to the center of Pin 1 of the header. Pin 1 center is about 0.3" from the top board edge, and the opposite side stand-off center is about 0.2" from the top board edge.

                              Board size is roughly 6.125" x 3.9". That ought to be enough of the critical dimensions to help anyone designing their own, or modifying a design for the best fit.


                              Now a question -- mine looks to have been reworked quite a bit. Seems factory. My board is stamped "6480099XM".

                              In addition to the typical yellow 10u/16v tantalum caps at C17, C18, and C19, there are three additional tantalum caps on the back side of the board -- one bodged in on the rails running down around dead center of each "bank" on the left and right sides of the board, and one on the bottom left (looking at the solder side, header on left.) They are labeled "15-20" and orange in color.

                              There are a couple 100n ceramic caps on the bottom left, and a whole cluster of 15p black film(?) caps on the top of each bank, soldered to the chip pins.

                              It also appears the positive rail has been cut, where it runs from the pin header to the bottom edge of the board. A ferrite choke has been installed in-line between the two new ceramic caps.

                              Anyone seen this before?

                              Comment


                                #45
                                The above sounds close to the one I got from someone who got them from Computer Reset. Mine has some hand written part numbers on it. My expansion card only seems to detect 192kb of memory.
                                when I run the IBM advanced diagnostics memory test, I get error 030201. I've replaced that module and moved others around in that bank but still get the error.
                                Does yours do the same?
                                You do not have permission to view this gallery.
                                This gallery has 2 photos.
                                I have a Major in Post-Apocalyptic Economics.
                                Wanted: Any PC-Compatible Reciprocation Dingle Arm

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