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Thread: 2megs ChipRAM on rev.6a Amiga 500 Motherboard

  1. #21
    djos's Avatar
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    Well put, I suspected this was the case but wasn't 100% sure.

    I use the expansions from kipper as they are true auto config fast ram.
    500 w/ KS1.3/3.1, 1Mb Chip-Ram, CF-IDE w/4MB Fast-Ram, FDD Selector, HxC RevC Floppy emulator Amiga 600 w/ KS1.3/3.1, 2Mb Chip-Ram, 1GB CF-HDD 1200 w/ KS3.1, ACA1220 26Mhz 128MB w/ RTC, 4GB CF-HDD, Roland MT-32 MIDI Synthesiser 64 w/ 1541 Ultimate-II + Tape Adapter, JiffyDOS, 1541 Disk Drive, 1531 Datasette, Flyer Net Modem

  2. #22

    Default Agnus chip info

    I think that I have some info on those 2MB AGNUS chips...

    The 318069-03 a 2MB AGNUS that is a two in one chip with a pin that sets NTSC or PAL. It is just like the 318069-02 1MB AGNUS that comes with the REV6a A500

    318069-16 1MB AGNUS A2000 (PAL)
    318069-17 1MB AGNUS A2000 (NTSC)
    318069-18 2MB AGNUS A3000 (PAL)
    318069-19 2MB AGNUS A3000 (NTSC)

    These four chips replaced the318069-02 and 318069-03 and were system specific.....and if you use one of these four chips, the board needs a little reworking....
    http://www.amigawiki.de/doku.php?id=dearts:agnus&s[]=agnus&s[]=reworks&s[]=pdf

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    Do we have the info needed to make similar mod to Amiga 2000 machines?

  4. #24
    8 Bit Dreams DjCook's Avatar
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    indded, useful info, does anybody tested it and found to be working?

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    @sjamaan, the big book of amiga hardware has this: Agnus (2MB) 8375 R0 318069-18 A500+ (PAL), A600 (PAL) but you have it as the PAL Agnus 3000. I previously picked up the 318069-03 as per original post (and prepared to do the minor jumper changes as described. With the 4 chips your listed, is any modification needed? Also, can you clear up the -18 conflict?

  6. #26
    Jack of Many Trades, Semi-Master of Some thebajaguy's Avatar
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    A500 Rev 8 motherboard, which supports both an A500 and A500+ out-of-box configuration, ONLY uses the 390544-01 or -02 2MB Agnus. This was the first Agnus with the radical pin out change from the 8372A variants in the Rev 6 A600, and the Rev 6.x A2000 and the B version in the A3000. they also went back to PAL/NTSC specific chips. If you have an A500 Rev 8, you can add the necessary parts (512K of 256x4 RAM to the mobo, 74-series logic chip, a 1M trapdoor expansion, clock parts, and a few misc resistor/cap parts present on a factory A500+) and get a 2MB ChipRAM A500+.

    The 8575 series from 318069 versions -16 to -19 have the classic 8372A/B pin out again - they are spares for former 8372A/B uses. (16/17 are for A2000 Rev 6.4/6.5 1MB replacements for the 8372A, but there is a jumper you need to add - see the A2000 specs for that rev-up past 6.3). The -18 and -19 PAL and NTSC A3000 2MB versions of the chip, intended for the A3000, and are PAL/NTSC specific now, and also require the same mod depending on the host and PAL/NTSC.
    Last edited by thebajaguy; 4th November 2017 at 03:48.
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    Just wondering if anyone can help, I've got an A500 rev 6A system that's had the 2 meg chip ram mod performed unsuccessfully. It has the 318069-03 Agnus, the jumpers are all set correctly, and there are four GM71C4400CJ60 RAM chips (1meg x4 60ns,on SOJ to DIP adapters) in U20-U23. It gives a black screen on Kickstart 3.1, and Diagrom gives a flashing assortment of colors on the screen. Running a Vampire V2 the system was loading and recognized the memory but was glitchy.

    Using the 68000 the system seems to run for a few seconds before stopping, the floppy drive will spin up and read a couple of tracks - then activity stops.

    I'm not seeing any errors from the CPU - no halt, reset or bus error, and there is activity on the address and data bus until a few seconds into loading when the activity stops.

  8. #28
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    Quote Originally Posted by Dipski View Post
    Just wondering if anyone can help, I've got an A500 rev 6A system that's had the 2 meg chip ram mod performed unsuccessfully. It has the 318069-03 Agnus, the jumpers are all set correctly, and there are four GM71C4400CJ60 RAM chips (1meg x4 60ns,on SOJ to DIP adapters) in U20-U23. It gives a black screen on Kickstart 3.1, and Diagrom gives a flashing assortment of colors on the screen. Running a Vampire V2 the system was loading and recognized the memory but was glitchy.

    Using the 68000 the system seems to run for a few seconds before stopping, the floppy drive will spin up and read a couple of tracks - then activity stops.

    I'm not seeing any errors from the CPU - no halt, reset or bus error, and there is activity on the address and data bus until a few seconds into loading when the activity stops.
    The Ram you acquired from SIMMS might be EDO* or something similar - I'd just grab some real 514400 DRAM DIP chips, they are usually dirt cheap!

    *I'm not even sure if Fast Page DRAM ram would be compatible
    Last edited by djos; 17th April 2018 at 10:56.
    500 w/ KS1.3/3.1, 1Mb Chip-Ram, CF-IDE w/4MB Fast-Ram, FDD Selector, HxC RevC Floppy emulator Amiga 600 w/ KS1.3/3.1, 2Mb Chip-Ram, 1GB CF-HDD 1200 w/ KS3.1, ACA1220 26Mhz 128MB w/ RTC, 4GB CF-HDD, Roland MT-32 MIDI Synthesiser 64 w/ 1541 Ultimate-II + Tape Adapter, JiffyDOS, 1541 Disk Drive, 1531 Datasette, Flyer Net Modem

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    Thanks for the reply. They were indeed taken from a working SIMM - the chips are Fast Page DRAM, the pinouts are identical to the 514400 DIP chips and the specs are the same.

    When the mod was done they couldn't find DIP package chips at a sensible price, I found some but have to wait for up to 8 weeks shipping. They don't seem to be in great abundance any more, if you know anywhere that has them dirt cheap please let me know

    As the specs of the chips currently on the board are the same and it should work, I'm worried that I'll end back at square one but if nobody has encountered any issues with the mod then I imagine it must be an issue of some kind with the memory.

  10. #30
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    Quote Originally Posted by Dipski View Post
    Thanks for the reply. They were indeed taken from a working SIMM - the chips are Fast Page DRAM, the pinouts are identical to the 514400 DIP chips and the specs are the same.

    When the mod was done they couldn't find DIP package chips at a sensible price, I found some but have to wait for up to 8 weeks shipping. They don't seem to be in great abundance any more, if you know anywhere that has them dirt cheap please let me know

    As the specs of the chips currently on the board are the same and it should work, I'm worried that I'll end back at square one but if nobody has encountered any issues with the mod then I imagine it must be an issue of some kind with the memory.
    Hmm, you are right, they have gotten very hard to find for a decent price!

    The most likely issue is some of the chips did not survive being removed and re-soldered. I assume you used a heat gun or hot air station to remove them?

    PS, Hi Dave
    Last edited by djos; 18th April 2018 at 01:39.
    500 w/ KS1.3/3.1, 1Mb Chip-Ram, CF-IDE w/4MB Fast-Ram, FDD Selector, HxC RevC Floppy emulator Amiga 600 w/ KS1.3/3.1, 2Mb Chip-Ram, 1GB CF-HDD 1200 w/ KS3.1, ACA1220 26Mhz 128MB w/ RTC, 4GB CF-HDD, Roland MT-32 MIDI Synthesiser 64 w/ 1541 Ultimate-II + Tape Adapter, JiffyDOS, 1541 Disk Drive, 1531 Datasette, Flyer Net Modem

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