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Old 15 April 2019, 21:35   #1
x56h34
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A500 rev 6A, motherboard 1MB chip ram, question about slow ram expansion.

Hi guys,

I own an Amiga 500 revision 6A unit that I have converted to 1MB chip ram by soldering additional 512k of ram directly onto the motherboard.

The slow ram expansion port is now empty.

If I were to buy and put a 512k ram card in there, would that work and show up as additional slow memory (making the grand total ram 1MB chip, 512k slow), or would it be undetectable?

My Agnus is the 1MB version.


Thanks,

x56h34


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Old 15 April 2019, 23:32   #2
zipper
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No, the same address space is used. Needs further modding.
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Old 16 April 2019, 00:39   #3
AmigaHope
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Quote:
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No, the same address space is used. Needs further modding.
To be more accurate -- the same physical address lines are used. You can hack further expansion for the $C0 Ranger memory block but you will have to run extra wires (probably to Gary) to do that.

That said, slow mem is... slow. The only reason to have it really is for compatibility with software that is hardcoded to use the Ranger address space, but the few bits of software that are badly-programmed this way pretty much all have WHDload patches.
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Old 16 April 2019, 08:59   #4
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To be more accurate -- the same physical address lines are used.
The same physical address lines are always shared between chip ram/slow ram banks, but to be even more accurate, the RAS lines overlap for the trapdoor and the second bank on the motherboard.
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Old 16 April 2019, 14:44   #5
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You could get your 6A to a grand total of 1 MB chip and 1.5 MB slow with Chris' or Pete's 2 MB ram expansion boards/mods, but you would have to undo your onboard ram mod first. That is why you should socket the chips for easy removal if you want to undo things later on.

http://eab.abime.net/showthread.php?t=93130

http://eab.abime.net/showthread.php?t=85395

If you for some reason need 2 MB chip ram in rev 6A you would need a fatter Agnus and then do this:

http://www.rasterline.com/images/ami..._2MEG_CHIP.jpg
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Old 16 April 2019, 17:37   #6
x56h34
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Thanks for your replies everyone.

OK, so not possible. Further modifications needed for any kind of RAM slot use. Good to know.

I really don't need more than 1MB chip ram, as this A500 is intended to stay in stock configuration mode, for simple retro gaming needs.
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Old 25 April 2019, 17:27   #7
AmigaHope
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If you can find one, I'd stick an RTC card there. (There do exist cards that just just had the RTC, or you can remove the RAM from an A501)
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