Raspberry PI Co-Pro 6502 more memory?

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Muddyfunster
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Raspberry PI Co-Pro 6502 more memory?

Post by Muddyfunster » Wed May 15, 2019 5:50 pm

Hi all,

I've been recently expanding my master and i've added the RPI Co-processor to it. I love the possibilities that this opens up.

I understand how to switch cores and so on but one thing I was wondering is if it's possible to increase the memory on the 6502 core to 128k to allow running of games like Stunt Car Racer with the Co-Pro.

It might be that SCR wouldn't even utilise it (no idea but I was curious to experiment and try).

Is it possible to adjust how much memory each core has as a default ?

I might be barking up the wrong tree with this but I thought I'd ask.

Cheers,

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hoglet
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Re: Raspberry PI Co-Pro 6502 more memory?

Post by hoglet » Wed May 15, 2019 6:05 pm

The 6502 Co Pro already has access to 2MB of RAM using bank switching.

The 6502 memory map is spilt into 8K pages via a set of paging eight registers at &FEE0-&FEE7:
- the register at &FEE0 controls the mapping of 0x0000-0x1FFF
- the register at &FEE1 controls the mapping of 0x2000-0x3FFF, etc

Each paging register takes an 8-bit value, providing access to 8K x 256 = 2MB.

There is a variant of the Co Pro Conway Life implementation that uses this bank switched memory support much larger patterns. More on in the [viewtopic.php?p=153721#p153721]Conway Life Thread[/url]

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danielj
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Re: Raspberry PI Co-Pro 6502 more memory?

Post by danielj » Wed May 15, 2019 6:47 pm

The extra memory on the master is very different to the RAM on the coprocessor, so unfortunately it won't let you run things that were developed specifically to work with the master (like SCR). The coprocessor just uses the computer it's connected to for inout/output (display, keyboard, disks etc). Games have to be written to work with it specifically - the only one I know of is the copro version of elite!

Muddyfunster
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Re: Raspberry PI Co-Pro 6502 more memory?

Post by Muddyfunster » Wed May 15, 2019 8:56 pm

Got it, thanks guys.

Every day is a school day for me with the Beeb at the moment :)

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