From: COPLIN, Nicholas. (
Date: 1999-11-19 02:35:26

Thanks for the information so far....

I downloaded a few core 6502 emulator codes yesterday and compiled to see if
its all worth while.... C-only coding examples give ~3Mhz emulation on a
P100 - probably not enough benefit to justify the pain... so will have to
find/code an assembler core... internet searching sounds easier than
coding... in my mind need 20Mhz benefit with a P100 (or 486/100) to making
worth while.....

I was thinking 8255 as they might save on real estate and the DMA access
need only be 1MHz (else trouble syncronising....).  Descrete buffers may
also do the trick....  I was thinking of even being lazier and doing it with
two/three LPT ports (old PC bus is ~7.xxMhz)

The other thought was to go straight to a 40pin "plug to the 6510 socket"
and thus not have to worry about port 0000/0001 and D000-DFFF area.....
mmm.... 1Mhz comms along a 30cm ribbon cable?!?!?

Step 1 i think is to identify the core emulator's speed.

- Nick

> -----Original Message-----
> From:	Marko Mäkelä []
> Sent:	Thursday, 18 November 1999 22:27
> To:
> Subject:	RE: C64 DMA
> On Thu, 18 Nov 1999 wrote:
> > The make sure evrything goes smooth, you put some NOPs behind the
> > instruction in case the timing is not quit right.
> I have never understood this.  I've seen unnecessary NOPs in the bank
> switching code of cartridges and in some other places.  It is hard to
> believe that there could exist a latch having a long enough propagation
> delay (over 300 ns) for an approach without any NOPs to fail.
> > The Z80 starts at $0000, its reset-address, the first time it is
> > activated. The rest is the same as with the 6510.
> According to the Programmer's Reference Guide, in the Commodore CP/M
> cartridge, the Z80 addresses do not directly correspond to 6510 addresses.
> I think it was off by $1000 ($1000 in the C64 memory would be $0000 in the
> Z80 address space).
> > I did not completely understand the above.
> I did.  He is planning to use the C64 for I/O of another computer system
> (this is just what accelerator cartridges do).  One Finnish guy asked
> about this in comp.sys.cbm recently; maybe you could co-operate with him?
> I think it's quite possible to use the cartridge port for write-only
> access to all of the RAM (maybe expect $d000-$dfff) and I/O.  By default,
> all other memory areas expect $d000-$dfff are write-through (when you
> write, the value will go into RAM), and by using the -GAME and -EXROM
> lines appropriately, you could perhaps be able to enable the RAM at
> $d000-$dfff for writing.  Add a wire running into the 6510's CHAREN
> output, if you cannot figure out any better solution.
> 	Marko
> -
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