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Old 27 July 2021, 00:00   #1
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Join Date: Feb 2019
Location: Zurich
Posts: 26
A600 1MB memory card showing up as 512kB?

I recently acquired a really crusty old A600 and have been making it work. It came with a AMPRO6001 trapdoor memory module, which had been badly mauled by the Varta battery (accurséd be their name...).

After removing the battery and lots of cleaning, it actually doesn't seem too bad. However, when I connect it to me A600 it appears as 512kB of 'graphics RAM' (I take it that's chip RAM). AFAICT this memory module is supposed to be 1MB. It looks like it's completely dumb, with no autoconfig ROM or memory mapping logic, and according to the memory map it should appear at the hard-coded address range of 0x100000-0x200000.

I've traced through the address and data lines and they all seem to be connected to the obvious places. I've cleaned all the contacts, too.

What could be wrong here, and how can I diagnose it? Does anyone know of a bootable bare-metal memory tester, memtest86-style (it's hard to test arbitrary address ranges when AmigaDOS is living in random bits of it...)?
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