Re: How hardware accelerators deals with $0/$01

From: Per Olofsson <magervalp_at_fastmail.fm>
Date: Fri, 27 Oct 2017 05:15:24 -0400
Message-Id: <1509095724.1989913.1152771320.4704E3E1@webmail.messagingengine.com>
On Thu, Oct 26, 2017, at 09:58 PM, Jesus Cea wrote:
> According to that if 6510 $0/$1 is CHAREN=HIRAM=LORAM=0, you have a flat
> 64 Kbytes internal RAM if GAME=1 (default if not cartridge) but you will
> have I/O at $D000-$DFFF if GAME=0 (and EXROM=1, default if floating).
> 
> In this mode there are external ROMs mapped in and I don't know if the
> VIC-II can see them,

Yes, in Ultimax mode the external ROMs are visible to the VIC-II.

> but if GAME is only zero when accessing $D000-$DFFF
> in a CPU access cycle, we get just what we want.
> 
> Is this the holy grail I was looking for?.

Back when I had a SuperCPU I didn't have a logic analyzer. Now I have a
logic analyzer, but I sold my SuperCPU. So I have no way of confirming
it, but afaict that's the way you have to do it - flip /GAME for half a
cycle when writing to $Dxxx.

-- 
  Per Olofsson
  magervalp@fastmail.fm

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Received on 2017-10-27 10:00:02

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