Re: PC-card (4)

jbevren_at_starbase.globalpc.net
Date: 2001-04-13 15:58:29

On Fri, 13 Apr 101 g.baltissen@hccnet.nl wrote:

> Hallo Bogax,
> 
> > I've never used the thing and perhaps I misunderstand what you're
> > saying, but you shouldn't need two 8237s.
> > Memory to memory is done with two DMA channels, channel 0 is the
> > source and channel 1 is the destination.
> 
> Found the section so you were right, thanks!
> 
> But now the bad news:
> The the 8237 needs FOUR cycles for every single operation. A DMA of one 
> byte from memory to memory  would cost eight cycles. OK, even when running 
> on 1 MHz it still is a better performance then when the CPU had to do the 
> job. But you can forget the real 1 MHz performance the REU can run. Until 
> now I haven't found an idea to speed things up except using 2 IC's. But 
> this only would permit 256KB/sec.

Remember: the 8237 will be clocked from the ISA bus, which runs at
8mhz! ;)


> 
> Anyone has ideas?
> 
> Groetjes, Ruud
> 
> http://Ruud.C64.org/
> 
> 
> 
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