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Old 08 November 2019, 14:46   #1
Sim085
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Is bottom expansion slot just for a clock board on an A500 rev5 with 8371 agnus?

Given the Agnus 8371 agnus supports 512K of RAM, and given a rev5 A500 board already comes with 512K of RAM onboard, then does it mean that such a machine, unmodified, would only support a clock board in the bottom expansion slot?
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Old 08 November 2019, 14:57   #2
hooverphonique
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It supports 512K of chip ram, but also slow ram, so you can put the traditional A501-style 512K expansion board in such an A500.
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Old 08 November 2019, 16:01   #3
AmigaHope
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Originally Posted by hooverphonique View Post
It supports 512K of chip ram, but also slow ram, so you can put the traditional A501-style 512K expansion board in such an A500.
Yup, the trapdoor was basically created for the A501, which was released at the same time as the A500. To the best of my knowledge C= did not release a clock-only expansion.

And this led to the evil practice of games authors assuming that any expansion memory would be located at the $c0... "Ranger" memory address range. It was so bad that even many later A500s that shipped with an ECS Agnus would use the A501 as Slow ranger memory by default.
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Old 09 November 2019, 15:59   #4
Sim085
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So when we say that Agnus is 512KB or 1MB or 2MB it means the amount of addressable ChipRAM only? If the Agnus is 1MB and in total on board and through bottom expansion slot there is a total of 2MB than 1MB can be addressed as ChipRAM and the rest will become slowRAM? is this correct?
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Old 09 November 2019, 17:34   #5
hooverphonique
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So when we say that Agnus is 512KB or 1MB or 2MB it means the amount of addressable ChipRAM only?
Yes.
Quote:
Originally Posted by Sim085 View Post
If the Agnus is 1MB and in total on board and through bottom expansion slot there is a total of 2MB than 1MB can be addressed as ChipRAM and the rest will become slowRAM? is this correct?
Yes and no. To address more than 512K slow ram, you also need a Gary-adapter, and possibly a cpu adapter.
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