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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: trekiej on May 15, 2016, 06:01:24 AM

Title: Amiga 500 REU
Post by: trekiej on May 15, 2016, 06:01:24 AM

I was wondering if it was possible to build an REU that would go into the memory slot of an A500.
It could have an 8 meg ram and work like an the C64 version.
It would also need to use some chip ram to work.

Title: Re: Amiga 500 REU
Post by: Matt_H on May 15, 2016, 06:25:56 AM

These exist, sort of. The trapdoor can only address an additional 512K so to get more RAM an additional adapter was necessary, e.g., http://www.bigbookofamigahardware.com/bboah/product.aspx?id=1015.

Then there's always the side expansion port, which can address the full 8MB directly.

Title: Re: Amiga 500 REU
Post by: trekiej on May 15, 2016, 06:32:12 AM

I hope you do not mind me saying, the C64 would look at the C64 memory to see if the cpu gave it a command. The REU would act on it then.

AdRAM 540 is a cool product.

Title: Re: Amiga 500 REU
Post by: Linde on May 15, 2016, 02:13:32 PM

I think the advantages the C64 REU way of moving/copying RAM via DMA to arbitrary locations diminish with the Amiga since it already has a blitter. If you just need big RAM on a small bus you'd rather use some sort of bank switching mechanism.

Title: Re: Amiga 500 REU
Post by: trekiej on May 15, 2016, 05:12:22 PM

I guess it is possible to do a lot of things with Hardware and Software. I feel the next part is finding out if it will perform well enough.
It would be interesting to see if Serializing the trapdoor expansion could be a way to expand an Amiga.

Title: Re: Amiga 500 REU
Post by: bbond007 on May 16, 2016, 01:18:57 AM

Quote from: trekiej;808494

I was wondering if it was possible to build an REU that would go into the memory slot of an A500.
It could have an 8 meg ram and work like an the C64 version.
It would also need to use some chip ram to work.

That how "Expanded" vs "Extended" memory worked on the DOS PC.

It was really only good for certain programs that knew how to take advantage of that type of RAM.

Its an Amiga, so you can take total control of the system and utilize that RAM for something, but it would take a major hack job to get the OS to understand how to use it as memory heap.

Title: Re: Amiga 500 REU
Post by: trekiej on May 16, 2016, 02:50:23 AM

Rom upgrade or added driver sounds like the answer.

Title: Re: Amiga 500 REU
Post by: psxphill on May 16, 2016, 07:58:56 AM

Quote from: trekiej;808494

I was wondering if it was possible to build an REU that would go into the memory slot of an A500.
It could have an 8 meg ram and work like an the C64 version.
It would also need to use some chip ram to work.

Yes, you would need ram and a dma controller.

If you did it in a reasonably large fpga you could have it do something funky like decompress video and convert it to ham and then dma it into chip ram to be displayed.

The cpu would likely get starved though.

Title: Re: Amiga 500 REU
Post by: trekiej on May 16, 2016, 04:53:42 PM

Sounds like timing could make it complicated.

Title: Re: Amiga 500 REU
Post by: Thorham on May 16, 2016, 05:17:39 PM

Apart from ease of installation there are only drawbacks to an approach like this.