RE: Article PC-card
Date: 2001-02-25 20:51:51

Hallo Nick,

> >Yes. But also tristates the address- and databus. And that is something
> that
> >does not happen with the PC-bus. And I'm very sure not even wanted.

> That's right, you don't want it... then 8237DMA controller is on the PC 
> mainboard and though the CPU is tri-stated, it controls read/writes 
> from/to IO/MEM.... if the concept is to have a PC card plug into the C64, 
> then someone has to be awake to make the transfer else a DMA controller 
> will be needed between the two.

I'm sorry, either you do not understand it, or I don't understand what you 
wrote. So for sure I repeat everything:
- the IOCKRDY line is to halt the CPU and nothing more. The CPU stops 
processing but address- and databus reamin active. My comment was that the 
6502 has this feature as well. But the trouble was that this input could 
not be used as it was not connected to the expansionbus.
Marko commented to use the DMA-input which resulted into my comment that 
this input could _NOT_ be used as using this input would not only result in 
stopping the CPU but also tristating the address-and databus. The IOCKRDY 
input was meant to be used by slow memory or I/O. You surely don't help the 
poor slow device by tristating the databus during a read....

As I understand, you say that we need a DMA controller before we can use a 
PC card? Why? The MGP card for example does not use DMA. And As I already 
said, it run fine with my C64 from 1989 on. DMA is only needed with 
floppies, harddisks and networkcards, at least for the PC. I already proved 
that the C64 doesn't need one for a IDE-disk (OK, speed is not "je-van-het" 
but...). I don't see any reason why it should not work for a 360KB floppy, 
for the 1.44 I have my doubts.

Groetjes, Ruud

This message was sent through the cbm-hackers mailing list.
To unsubscribe: echo unsubscribe | mail

Archive generated by hypermail 2.1.1.