RE: 16 MB REU clone
Date: 2001-09-01 06:53:35

Hello Ruud

>IMHO a 8237 is a generic DMA handler on itself. Very 
>roughly said, the REU
>is equivalent to two 8237's plus a refresh mechanism. 
>Unfortunately the registers don't match :(

True, but the 8237 an Intel chip. Brand loyalty aside, the problem is what
glue is needed to make it work. Have you got a circuit with it configured as
a 65xx bus compatible module. If it takes 5+ chips then one might as well
build their own controller...

>replacement for it or use something 'simple' like GEOS-RAM.

except much faster, point taken though - an REU is much more complicated
that a DMA engine, but the VHDL core for  DMA transfers could be written in
portable way.

>64HDD uses a PC-motherboard as core of the desig. It 
>sounds very logical to
>me to use its onboard DMA in the first place. And if you have other
>DMA-ideas, I still would use the 8237 as there is enough 

To access the PC's DMA capability needs either ECP if using an LPT port (for
a *blinding* 2.4Mbyte/s) or a PC card. I honestly cannot see too many people
plugging a hacker's wirewrapped card into their new 1.3GHz PentiumIV
computer (believe me, that's what some people are using to serve data to the
C64...). This makes using the on-board features unlikely.

- Nick


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