more RAM , how?

[motorollin]

HellCoder wrote:
If we can connect a PPC/PCI/USB to our amiga, why hasn't someone made a hardware thing to expand our chipmem ?Just a thought.

The 2MB chipmem limit is a limitation of the Amiga's custom chips. If you wanted more chipmem, you would have to replace the custom chips with new versions which supported more RAM.

PPC cards, PCI busses and USB controllers are not subject to this limitation as they do not rely on the custom chips (except to load driver software or libraries, which are small enough to fit in 2MB chipmem or can be coded to use fastmem).

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moto

[motorollin]

Piru wrote:

If you wanted more chipmem, you would have to replace the custom chips with new versions which supported more RAM.

It should perhaps also be pointed out that there is no such custom chips available.

Of course :-)

Piru wrote:
2MB is the chip memory limitation in hardware. WinUAE can have upto 8MB "chip" memory, though.

Yes but then you have to use Windows  :-P  :-P  :-P  :-P  :-P

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moto

[motorollin]

If I understand correctly, this is basically a paging file? So the custom chips fill up the 2MB physical RAM chips, then when they require more memory some pages of RAM are moved to a file, thus freeing up chip RAM. Is this right? Could the memory pages be swapped in to fast RAM instead to make it faster? Presumably the ROM would have to be patched to make use of the page swapping rather than just refusing to run the application when no physical chip RAM is available.

Is any of this actually possible?

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moto

[motorollin]

Interesting. So there would be hardware in between the custom chips and the memory which can tell when the first bank of 2MB chips is full, then automatically switches to the second bank?

If the custom chips are addressing the same memory range no matter what bank was being used, how would the controller know which bank the required page is on?

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moto

[motorollin]

HellCoder wrote:
Perhaps you could say,.. Paula has map one, and Denise map two giving them both 2 MB each ?

That would seem to be cleaner. Is it only Paula and Denise who address chipmem?

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moto

[motorollin]

So who's gonna build this thing then? I want 128MB of chipmem :-)

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moto

[motorollin]

Because it's there :-)

Also, there are still some games which need 2MB of chipmem, so have to be run with no startup-sequence.

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moto

[motorollin]

Piru wrote:
There are other problems aswell: Software gets pointer to allocated memory (say above 2MB). Software pokes the address of the memory to custom chip register. The problem here is that the higher order bits are just ignored, so the chip (and thus the hw sniffing the address lines) has no way of knowing which bank it should access.

That's kind of what I was getting at when I said:

motorollin wrote:
If the custom chips are addressing the same memory range no matter what bank was being used, how would the controller know which bank the required page is on?

Piru wrote:
Forget it.

Forgotten :-)

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moto