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Loading dos high on a XT

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    Loading dos high on a XT

    Hallo allemaal,


    I expanded my XT with 128 KB of SRAM in the D- and E-area. For the schematics please see: http://www.baltissen.org/images/umb4xt.png
    Using the right UMB driver I managed to LOADHIGH various drivers like ANSI.SYS and my mouse driver. But it didn't work out for DOS. It seems that HIMEM.SYS is reponsible and that program won't work on a XT.

    My question: does anyone have an idea how I can persuade DOS to load itself high in my UMB memory?

    One idea of myself: emulating INT 15h in one or another way but then: how to tell DOS to load itself into the UMB area instead of the not-existing HMA area?


    Groetjes, Ruud Baltissen
    www.Baltissen.org
    With kind regards / met vriendelijke groet, Ruud Baltissen
    www.Baltissen.org

    #2
    Using PC-DOS 2000, USE!UMBS and DOSMAX I managed to load DOS in UMB memory with a self-made ISA ram card (similar to yours I think, but mine used two 64kb SRAM ICs and a 74LS138 )


    My videos:
    IBM PS/1 model 2011 restored and enhanced
    IBM PC Advanced Diagnostics Cassette load

    Comment


      #3
      Originally posted by nestor View Post
      Using PC-DOS 2000, USE!UMBS and DOSMAX I managed to load DOS in UMB memory with a self-made ISA ram card (similar to yours I think, but mine used two 64kb SRAM ICs and a 74LS138 )
      nestor, can you please provide more details?

      Here is my schematics for memory extension card. It allows mapping of up to 192 KiB memory (from 0C0000h to 0EFFFFh) to UMB, that can be enabled on 32 KiB block basis (depending on other devices that use high memory). It also adds memory in 80000h to 9FFFFh range (from 512KiB to 640 KiB), this could be disabled if needed.

      Hopefully your method will make it work too. Also it is interesting if it is possible to have "holes" in UMB.

      Comment


        #4
        Also, look at the 1Meg mod for the 5160 using 4 banks of 256K DRAM and replacing the mapping ROM. It gives the same 128K between D0000 and EFFFF without adding any cards.
        Reach me: vcfblackhole _at_ protonmail dot com.

        Comment


          #5
          I thought DOS already loaded high up in ram.

          The non-resident portion that is.

          Ok never mind never mind. I didn't post this.

          Comment


            #6
            Originally posted by Chuck(G) View Post
            Also, look at the 1Meg mod for the 5160 using 4 banks of 256K DRAM and replacing the mapping ROM. It gives the same 128K between D0000 and EFFFF without adding any cards.
            I can testify for this! The 1MegXT mod works great. I get the same results as Nestor Using PC-DOS 2000, USE!UMBS and DOSMAX. The only drawback I can see is that we haven't figured out how to make it work on any of the XT clones.

            Anyone with a True Blue IBM XT 5160 or 5155 interested in the 1megXT mod, let me know, either here or by PM. I can provide the GAL and Adapter for cost of shipping.

            Comment


              #7
              Originally posted by Chuck(G) View Post
              Also, look at the 1Meg mod for the 5160 using 4 banks of 256K DRAM and replacing the mapping ROM.
              I did the hack with an 8 MHz board. But my 10 MHz board has one big IC taking care of 90% of the functions of the board, including managing the DRAM. And that was the reason to build this card.
              An advantage of this card: it doesn't needed to be initialised. If you don't do that with the DRAM, you surely get a parity error the first moment you access it. That's what happened I used USE!UMBS the first time with my 8 MHz board. I solved this problem by letting my BIOS taking care of this. How did you solve it?
              With kind regards / met vriendelijke groet, Ruud Baltissen
              www.Baltissen.org

              Comment


                #8
                I don't remember, but ibmapc certainly would--or you can search for the 1Meg thread here.
                Reach me: vcfblackhole _at_ protonmail dot com.

                Comment


                  #9
                  Originally posted by RuudB View Post
                  I did the hack with an 8 MHz board. But my 10 MHz board has one big IC taking care of 90% of the functions of the board, including managing the DRAM. And that was the reason to build this card.
                  An advantage of this card: it doesn't needed to be initialised. If you don't do that with the DRAM, you surely get a parity error the first moment you access it. That's what happened I used USE!UMBS the first time with my 8 MHz board. I solved this problem by letting my BIOS taking care of this. How did you solve it?
                  Chuck wrote a little device driver CLEARMEM.ZIP
                  First line in config.sys(or one of the first before use!umbs.sys) would be "device=c:\clearmem.sys d000 2000" .
                  This will clear d000 thru efff (2000 paragraphs starting at d000), taking care of the parity error problem.

                  Here's the 1MegXT thread that Chuck reffed to. It's a little long but there's some good info in there.
                  Last edited by ibmapc; July 17, 2012, 10:21 PM.

                  Comment


                    #10
                    Originally posted by sergey View Post
                    nestor, can you please provide more details?
                    My memory extension card is very simple: a 74LS138 is used to chip-select a 64KB SRAM IC for D0000-DFFFF area and other 64 KB SRAM IC for the E0000-EFFFF area. That gives a 128 contiguous UMB memory, but the OS can't use them directly. Here enters USE!UMBS.SYS, a free driver that enables UMB using RAM in the D0000-EFFFF area. Once loaded, you can use loadhi and devicehigh to load drivers and trs in upper memory.

                    To load DOS itself in UMB, I use DOSMAX. It is a free driver to load DOS in UMB memory.
                    My videos:
                    IBM PS/1 model 2011 restored and enhanced
                    IBM PC Advanced Diagnostics Cassette load

                    Comment


                      #11
                      Originally posted by nestor View Post
                      Here enters USE!UMBS.SYS
                      IIRC I got the software from the developer himself in 1991. But just out of curiousity I searched the internet for it but couldn't find it. If there is interest, I'll put it on my site so others can download it. FYI, my version includes the source code.

                      To load DOS itself in UMB, I use DOSMAX.
                      I found DOSMAX17.
                      One question: how does your CONFIG.SYS and AUTOEXEC.BAT look like?
                      With kind regards / met vriendelijke groet, Ruud Baltissen
                      www.Baltissen.org

                      Comment


                        #12
                        Originally posted by RuudB View Post
                        IIRC I got the software from the developer himself in 1991. But just out of curiousity I searched the internet for it but couldn't find it. If there is interest, I'll put it on my site so others can download it. FYI, my version includes the source code.


                        I found DOSMAX17.
                        One question: how does your CONFIG.SYS and AUTOEXEC.BAT look like?
                        I found USE!UMBS here: http://cd.textfiles.com/cream/cream06/utility/ (look for use_umbs.zip file)
                        It comes with the source... the only thing that I will improve (if and when I have time) is command line options for specifying UMB memory ranges. Now it's just hard coded.

                        Comment


                          #13
                          Originally posted by sergey View Post
                          the only thing that I will improve (if and when I have time) is command line options for specifying UMB memory ranges.
                          I already was working on a version that checks the memory itself. Not handy but I simply didn't think about the command line option. I only thought about when seeing the DOCs that goes with DOSMAX yesterday evening. From next week on I have time, so could you do me a favour and point me to an URL or give me instructions how I can check the command line using assembly?
                          Many thanks! Results will be freeware of course.
                          With kind regards / met vriendelijke groet, Ruud Baltissen
                          www.Baltissen.org

                          Comment


                            #14
                            Originally posted by RuudB View Post
                            I already was working on a version that checks the memory itself. Not handy but I simply didn't think about the command line option. I only thought about when seeing the DOCs that goes with DOSMAX yesterday evening. From next week on I have time, so could you do me a favour and point me to an URL or give me instructions how I can check the command line using assembly?
                            Many thanks! Results will be freeware of course.
                            The command line (anything after DEVICE=...) is passed with the driver initialization call to the driver. The address to command line is stored in the request header starting from offset 12h (decimal 18 ), it is a 4-byte pointer with segment and offset. See this (look for "driver initialization call").

                            You'll need to implement parsing of the command line (validate its correctness, translate ASCII/hex to binary). Discussed in other thread 2M-ABIOS/2M-XBIOS floppy BIOS extension has a code for parsing device driver's command line. The source code can be found here (note: comments in the code are in Spanish). Perhaps this can be used as an example of command line parsing.

                            The USE!UMBS comes with memory auto-detection utility (TEST!UMB?!), but it looks not very reliable, e.g. it might report VGA memory or shared memory of an Ethernet card as UMBs, but I doubt anyone will want to use this memory for UMB purpose. So I don't think it is a great idea to implement auto memory detection in the driver itself.

                            Comment


                              #15
                              I'm with sergey, auto-detection would be prone to misidentify unusable UMB RAM and honestly, the few people that are interested in using UMB in XT know exactly the amount and location of the UMB blocks.

                              Here are the contents of my actual AUTOEXEC.BAT / CONFIG.SYS files:

                              Code:
                              @ECHO OFF
                              SET COMSPEC=C:\COMMAND.COM
                              SET PATH=C:\DOS
                              SET TEMP=C:\DOS
                              LH C:\DOS\MOUSE.COM
                              LH C:\DOS\DOSKEY.COM
                              Code:
                              FILES=30
                              BUFFERS=20
                              COUNTRY=034,850,C:\DOS\COUNTRY.SYS
                              DOS=UMB,HIGH
                              DOSDATA=UMB
                              DEVICE=C:\USE!UMBS.SYS
                              DEVICE=C:\APPS\DOSMAX\DOSMAX.EXE /R+ /N+ /P-
                              DEVICEHIGH=C:\DOS\SETVER.EXE
                              DEVICEHIGH=C:\DOS\DISPLAY.SYS CON=(,,1)
                              DEVICEHIGH=C:\APPS\2M\2M-XBIOS.EXE A:4 B:0 /13
                              SHELL=C:\APPS\DOSMAX\SHELLMAX.COM C:\COMMAND.COM C:\ /E:256 /P
                              Last edited by nestor; July 19, 2012, 10:35 AM.
                              My videos:
                              IBM PS/1 model 2011 restored and enhanced
                              IBM PC Advanced Diagnostics Cassette load

                              Comment

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