Re: Using large DRAM modules inside the C64

From: Gábor Lénárt (
Date: 2005-10-11 12:53:54


I think it's quite compilcated to work with refresh in this case. I've
tried to use SRAM module, which is much easy, since you haven't need
refresh :) Also with a little battery it's possible to use SRAM as
some storage, because in stand-by mode it won't forget content with using
only a very low current from the battery. And nowdays SRAM is not expensive
at least ... It's not too hard to replace 6510 CPU with some 65816, and
all of the SRAM can be addressed directly by 65816 "mapped" above the
base 64K (which is the internal memory map of the base c64 of course).
At least I had a plan to do this, but I hadn't got enough time ever ;-(
I had also plans to think about clock 65816 faster than the original clock
of C64's 6510 with using some "wait states" when generating addresses to
the first 64K of memory (C64's original memmap) to much with the original
timing of the 6510. But when addressing "above" 64K, these wait states
can be avoided, so it would be faster (also the bus timing can be relaxed,
even VIC cycles should not disturb the CPU when addressing memory above 64K,
since it's the SRAM which should be done through an "internal" bus which
only connects the SRAM with the CPU and nothing to do with eg VIC. sure
it would require some additional stuffs to do it). 

Is it a very crazy idea, or can it be done at least?

- Gábor

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