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1MB on XT Macine

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    1MB on XT Macine

    Is there any purpose to installing the full 1MB that the 8088 can address on a PC XT/5150? Or is 640KB really the maximum that your computer will actually use?

    #2
    Spreadsheets, databases, etc. that use EMS might use it.

    You can have a RAMdrive.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

    Comment


      #3
      You'll never get 1MB of RAM conventionally addressed (i.e. not EMS or other bank-switching schemes) on an 8088/8086 PC-compatible because some portion of the address space is permanently set aside for BIOS and video adapters.

      However, there are ways that allow you to reclaim areas in the top of the address range, say Dxxxx and Exxxx addresses for RAM.

      Comment


        #4
        Originally posted by willmurray461 View Post
        Is there any purpose to installing the full 1MB that the 8088 can address on a PC XT/5150? Or is 640KB really the maximum that your computer will actually use?
        Using more than 640K (without adding an EMS board) requires additional hardware and software, and the list of programs on 8088 that can benefit from it is very small. For an 8088-class system, 640K is more than acceptable.
        Offering a bounty for:
        - A working Sanyo MBC-775 or Logabax 1600
        - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

        Comment


          #5
          Also see chestnut. Doesn't require additional boards in a 5160.

          Comment


            #6
            True, but I wrote additional hardware, and chestnut requires a hardware mod. These are out of the realm of novices, which the OP's question betrays him as.
            Offering a bounty for:
            - A working Sanyo MBC-775 or Logabax 1600
            - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

            Comment


              #7
              Originally posted by Trixter View Post
              True, but I wrote additional hardware, and chestnut requires a hardware mod. These are out of the realm of novices, which the OP's question betrays him as.
              Hmmmmmmm...
              PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

              Comment


                #8
                This Thread is an excellent write up for the 1 Meg XT Mod. that Chuck(G) referenced in his "chestnut" written by forum member pcdata76. It is still somewhat involved, but pcdata76 makes it pretty clear without needing to read through the entire thread that I started years ago.

                If you are serious about this mod, I can provide a programmed GAL.

                Greg

                Comment


                  #9
                  I don't need 1MB of RAM. I was just curious if it had any practical applications since I had an extra RAM expansion card lying around.

                  Comment


                    #10
                    Well, now you have your answer.

                    The need for more RAM was largely due to the popularity of Lotus 1-2-3 on the PC XT. Handling large spreadsheets by paging to slow hard disk was a real bottleneck. The best way was to use an EMS card, originally called "LIM" for the "Lotus/Intel/Microsoft specification". Other applications used it as well. For example, I've got an XT with an Intel Aboveboard 2MB installed and much of the MSLANMAN networking software will install in the EMS memory.

                    Comment


                      #11
                      Originally posted by Stone View Post
                      Hmmmmmmm...
                      Okay, I should backtrack on that one, given that he just restored a 3270 PC. No disrespect meant. What I meant was "novice in this area". Generally, anyone asking "is 640k the maximum your computer will use" is generally not prepared for the answer, either in configuration effort or in tracking down software that might actually use more than 640k via any means.
                      Offering a bounty for:
                      - A working Sanyo MBC-775 or Logabax 1600
                      - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

                      Comment


                        #12
                        Some software did have the ability to map extra memory into the 640k-704k region at the cost of not being able to use EGA or VGA graphics. It was beneficial for Desqview and DOS databases.

                        Comment


                          #13
                          I have a card with software that can extend DOS, reach to either 704K or even 896K:

                          http://www.vcfed.org/forum/showthrea...Expansion-card

                          http://www.vcfed.org/forum/showthrea...-card-for-5170
                          PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

                          Comment


                            #14
                            Sure, there were even one or two "almost PC" clones that populated the space between 0xA0000 and 0xB0000 with RAM giving 704K--and a couple "not even PC-ish" that used almost the entire 1MB space for RAM (video was handled by serial I/O). There's no absolute reason for 640KB other than IBM's convention. Plain MS-DOS runs fine on any of these.

                            Comment


                              #15
                              A while back someone had mentioned that it was possible to load DOS 5 in to an upper memory block on an 8088 similar to how it is loaded in to HMA on a 286. Of course that assumes an add on card or motherboard modification is mapping RAM in the upper memory area. Never tried that myself, and usually DOS 3.3 or 3.31 is a better fit for an 8088/8086 class machine anyway.

                              Practically speaking, loading a mouse driver, part of a network stack, or resident utilities in to an upper memory block can sometimes be handy while keeping conventional 640k free for applications.

                              Comment

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