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A500 (r6a) 1MB CHIP RAM Modification: Caution dialup users: excessive H/W pr0n!

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  • #31
    Worked a treat.




    Also solved my boot menu problem on 2.04 ks.
    A1200 1D.1/Apollo 1240 68040/45Mhz/32MB -White
    A1200 1D.4/68020/Blizzard 1200/4MB - Black

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    • #32
      As I am too lazy to flounder in my C= books, can someone confirm me the Agnus 8372A have two CAS lines, but only one RAS?

      I think that's what stops using the A501 as 512kb slow-fast RAM...
      _______________

      Or, pondering what I'm pondering, can other brave soul swap the CASL to CASU lines on the trapdoor pins and run a wire from Gary's A21 pin to the cut-down JP7A? This will fool the Amiga to force the trapdoor memory to act as slow-Fast while the motherboard will have the full 1Mb chip RAM.
      Last edited by rkauer; 22 August 2010, 22:38. Reason: language kixing
      David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
      16 Amigas at home
      3x C= 64
      1 VIC-20
      8 PC (argh) at least one is an AROS/Amithlon unit

      Comment


      • #33
        @TheoryBoy

        Great Stuff


        @thread

        Just to officially confirm, I have an 8375 - 318069-10 Agnus (2MB capable) Agnus working directly in my A2000 rev 6 (only 1MB at the moment though )

        So this confirms its a "drop in" component for all the PLCC Agnii based machines (except A500+)


        @rkauer

        My friend, I do beleive the EXRAM signal (JP7A) from gary is used to bank the trapdoor port.

        Because the onboard (unpopulated ram sockets) are tied to the trapdoor port to get the extra 512kb slow you would need assert a Garry Address and MultiPlex EXRAM (JP7A) for when Agnus is LOW.

        Now I am pretty sure you are correct with the Agnus port not having enough RAS lines for a second 1MB - I also think that your ponder of swapping out the LCAS UCAS signals to the trapdoor port and a little A21 asert - you could get the 512KB, buuuuuut, if the lcas/ucas are not cut from the port (and then implemented with jumpwire this will cause issues with the existing 1MB of ram.

        Hmmmm pondery ponders methinks =)
        Flux Mastah' Zee
        50 L337 1'M W1R3FR4M3

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        • #34
          I was thinking hard on the matter last two days, and two things are known: the EXRAM signal from Gary is necessary to the Amiga know there is something hooked to the trapdoor connector, as then the Amiga puts that expansion in the slow RAM address. This is transparent to the system.

          The device commonly have the same RAS & CAS lines as the Amiga chip RAM. Look in the slow RAM expansions: they all just use a multiplexer and two TTL buffers! So it's only a matter of redirecting the c00000 address to the expansion connector again after doing the 1Mb chip hack on the motherboard to have 512kb FAST RAM and activate it automagically!
          David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
          16 Amigas at home
          3x C= 64
          1 VIC-20
          8 PC (argh) at least one is an AROS/Amithlon unit

          Comment


          • #35
            I like what I am reading...

            I wonder how that would work though with the 8370 (half meg) Agnus?
            Flux Mastah' Zee
            50 L337 1'M W1R3FR4M3

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            • #36
              I think that will not work at all when using a 512kb-only Agnus. But since I have at least 3 8372A-equipped A500 here...
              David Bradley made Ctrl+Alt+Del, Gates turn it mandatory
              16 Amigas at home
              3x C= 64
              1 VIC-20
              8 PC (argh) at least one is an AROS/Amithlon unit

              Comment


              • #37
                Update

                because guildserver hosting is currently suspended - I have uploaded these images

                The basic overview



                JP2


                JP7A
                Last edited by rkauer; 6 February 2011, 02:47. Reason: trying to make pictures show.
                Flux Mastah' Zee
                50 L337 1'M W1R3FR4M3

                Comment


                • #38
                  Originally posted by Zetr0 View Post
                  Update

                  because guildserver hosting is currently suspended - I have uploaded these images

                  The basic overview



                  JP2


                  JP7A

                  I cant see the pics
                  OS4Depot http://www.os4depot.net/ - Its like Aminet for OS4!
                  RunInUAE http://cshandley.co.uk/ - No NextGen Amiga should be without this!

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                  • #39
                    no pics here either

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                    • #40
                      how strange - I ca see them here =/

                      heres some thumb-links (click to zoom)

                      Modification Diagram


                      JP7A


                      JP2


                      are these functioning okay?
                      Flux Mastah' Zee
                      50 L337 1'M W1R3FR4M3

                      Comment


                      • #41
                        Yes they are, however the original postings "lost" every picture I remember this thread with pictures. It was a nice hack-thread.
                        Proud on the classics: A1000-A500-A2000-A600-030-A1200 PPC -A3000D(basic)-A4000D(060)
                        Mac Mini 1.45 ghz 1 G RAM MORPHOS 2.6
                        Pentium 3 1.4 ghz 512 sdram AROS

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                        • #42
                          Thanks my friend,

                          I do have the original pics somewhere, I will dig them up when I get time and upload them again.
                          Flux Mastah' Zee
                          50 L337 1'M W1R3FR4M3

                          Comment


                          • #43
                            Originally posted by Zetr0 View Post
                            how strange - I ca see them here =/

                            heres some thumb-links (click to zoom)

                            Modification Diagram


                            JP7A


                            JP2


                            are these functioning okay?
                            I can see these ones Zeets
                            OS4Depot http://www.os4depot.net/ - Its like Aminet for OS4!
                            RunInUAE http://cshandley.co.uk/ - No NextGen Amiga should be without this!

                            Comment


                            • #44
                              Got a Rev 5? JP2 re-jump is done as per Z-man's tutorial, BUT there is no JP7A.

                              No problem, just look at where the trapdoor expansion plugs in & cut a track as shown here:



                              Obviously you'll need an 8372A Agnus for this to work

                              PZ.

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                              • #45
                                @Fingerz

                                I missed this update!! Great stuff!!

                                A point to note though - an 8371 is also 1MB compatible for chip, its the 8370 thats only 0.5MB (512KB Chip only)
                                Flux Mastah' Zee
                                50 L337 1'M W1R3FR4M3

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