1mb chip ram with aca500plus on rev5 motherboard

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  • Hello,


    I have my aca500plus connected to a rev 5 motherboard. I have an amram-x 512kb expansion, and an 8372A Fat Agnus and decided to give upgrading to 1mb chip ram a try.


    I have cut JP2 and soldered the top pads as per instructions on the net. According to what I'm reading all I should need to do now is turn the amram-x to "off" and it should be detected as chipram. However the aca500plus lists the ram as "unavailable" when I do this, when I turn it on and boot the Amiga it sees the ram as built-in (forget the exact term) and boots fine. I have _not_ cut the line near the trapdoor (EXRAM) because I from what I read the off/on switch on the Amram-x should take care of that.


    However, I am having some issues with the upgrade as it seems that SysTest (crashing) and other utilities designed to check memory are finding errors. I was hoping to confirm the proper settings for this configuration so I can 100% rule out a configuration problem and move on to hardware troubleshooting. I am wondering what the various ram options should be set to? Currently they are (with the ram switch ON - because OFF == aca500plus doesn't see ram)

    • $C0/Trapdoor RAM: disabled
    • 7M Fast RAM: max
    • 1M Chip RAM expansion: built-in

    I read somewhere that I might need to make a modification related to the ROM (apparently EPROM based ROM chips require extra wiring), but I am not 100% sure what to do about this since my ROM is technically coming from the aca500plus.


    Any help or insight you could provide would certainly be appreciated. Thank you!

  • I have cut JP2 and soldered the top pads as per instructions on the net.

    You've already done too much. This modification is not required any more with the ACA500plus. Please revert it to original and keep the 512k memory expansion switched on. The ACA500plus will then offer 1MB Chipram mapping.



    I read somewhere that I might need to make a modification related to the ROM

    Ignore that - all Kickstart versions ever available are finding more chip ram automatically.

  • Jens thanks. So, to be clear, on a rev 5 motherboard all that needs to be done to get 1 meg of chipram is to:


    - replace Fat Agnus 8371 with an 8372A,

    - switch on the chipram option and turn off $C0/Trapdoor RAM in expert settings


    Can I suggest that you make a note about this in the Wiki? As far as I can see it's not documented, and it might help out anyone in my situation in the future.


    Edit: One last question, would there be any problem on the aca500plus with flashing the DiagROM so I can test the memory expansion I have?


    Thanks very much.

  • - switch on the chipram option and turn off $C0/Trapdoor RAM in expert settings

    No need to mess with $c0 memory, as the ACA500plus provides that. The ACA500plus just maps the trapdoor expansion to $08.0000, making it available as Chip Ram if the Agnus is the right version.


    So the only modification is really to insert the 8372a Agnus, and only if you like it better in hardware than in software, make the required changes for letting it start in PAL mode (it will launch in NTSC mode on a Rev.5 board if you just insert it).


    Can I suggest that you make a note about this in the Wiki?

    It's in the product description, advertised as an outstanding feature: 1MByte chip ram without soldering, and even without opening the computer in many cases (Rev.6 boards have almost all been shipped with the 1M Chip ram Agnus). We have lots of customers who ask how this is possible without soldering, and who give emotionally-positive feedback about this very feature after they've seen it work for the first time. I wonder if people may see it as redundant/unnecessary information if it's mentioned in the Wiki again.


    Edit: One last question, would there be any problem on the aca500plus with flashing the DiagROM so I can test the memory expansion I have?

    Any Kickstart is fine. I haven't tried the DiagROM myself, but I see no reason why it should fail. Worst thing that can happen is that it does not work, and you need to do a reset or power cycle.

  • Thanks for the clarification Jens your time is appreciated!


    I did read the wiki, several times. I even tried to search for "chipram" to make sure that I wasn't missing something. I think that the wiki would benefit from a bit of additional clarification so that folks like me are _absolutely clear_ how to set up their aca500plus in this scenario.


    Could you please clarify for me the three settings I mentioned earlier:

    • $C0/Trapdoor RAM
    • 7M Fast RAM
    • 1M Chip RAM expansion

    For a 1meg chip ram setup, what *exactly* would these be set to? I am not sure what you mean by "No need to mess with $c0 memory"... does this mean I leave it as default, turn it off, etc? So you providing the exact options for a know-good 1meg chipram config would help folks experiencing problems (like bad memory) rule out aca500plus config as the reason.


    Thanks very much!

  • Could you please clarify for me the three settings I mentioned earlier:

    $C0/Trapdoor RAM
    7M Fast RAM
    1M Chip RAM expansion

    Press F1 in the startup menu, and this will automatically be set if you have an ECS Agnus and a 512k trapdoor expansion.

  • Jens, can you explain this part when you said:


    "make the required changes for letting it start in PAL mode (it will launch in NTSC mode on a Rev.5 board if you just insert it)."


    Isn't the IC 8372A PAL/NTSC ??


    What changes are you talking about?

  • We have them in stock, but they're not in the shop. Give me an hour; need to take a photo and make a product description.


    Edit: Check the shop now; item added.

  • Yes i see it! :thumbup:


    This is great so I can buy all in the same place.


    Today I'll submit my order of it + one beautiful ACA500Plus :love:


    Thank you Jens!


    EDIT: order submited!

    Please send me a newer Agnus from 1991 or later :saint:

    Thank you again Jens. :thumbup:

  • Please send me a newer Agnus from 1991 or later

    I have no control over that; sorting the chips by date code would mean a lot of extra labour that can't possibly be paid by the symbolic amount that we charge for these chips. Besides, the part number is the same, and after 29 years, one year difference in production date should not make a difference at all.