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Old 31 May 2020, 23:37   #23
roondar
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Join Date: Jul 2015
Location: The Netherlands
Posts: 1,959
Quote:
Originally Posted by VladR View Post
Yeah, I definitely didn't realize that. I'm still new to the Amiga thingy and keep getting confused about all those terms, as I didn't spent last 3 decades reading up on all those terms.
Ah yes, I do apologise for not making that clearer. Yes, fast memory (and ROM for that matter) can be accessed by the CPU without impacting the Blitter or the CPU being impacted by DMA. The A500 normally has no fast memory though, so for that platform it would not matter.

Even the "trap door" memory expansion on the A500 is not actually fast memory, but something called "slow memory". That is the worst of both worlds: slow memory can't be used by the custom chips (because it isn't chip memory)*, but it is slowed down by DMA on the chip memory bus

*) note that even here there are caveats: from a certain revision onwards, the A500 contained a version of Agnus that can access (some or all of) trap door memory as chip memory. Confusion all around then
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