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Haze
Reged: 09/23/03
Posts: 4394
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Re: Update
11/27/17 12:11 AM


> > > Edit: Wow, West Story seems to be running slower than what it should be. Does the
> > PCB
> > > have inadequate hardware, or was that just a result of the hackers messing with
> the
> > > code?
> >
> > The bootleg hardware is indeed less powerful. The original Seibu hardware
> apparently
> > used DMA to buffer the video RAMs (as all later Seibu games do). The bootleggers
> > didn't implement that and instead hacked up the 68000 code to laboriously copy out
> > the video memory in software.
>
> That's crazy. Will MAME be able to reproduce this behavior correctly?

It's not really complex, except for the possible waitstates / delay the DMA might cause periodically if you want to be 100% spot on with the timing.

A lot of other bootlegs have a 2nd copy of sprite ram and code to transform sprite lists from one format to another too, obviously this takes CPU cycles to do. Then you have bootlegs of bootlegs which do that, but where it's been confirmed on the PCB that the 2nd copy of spriteram isn't even the one that gets used (and infact, the ram doesn't exist, the code copies to nowhere)

All good fun







Entire thread
Subject Posted by Posted on
* DU: Blood Bros. SmitdoggAdministrator 11/26/17 08:19 PM
. * Update SmitdoggAdministrator  11/26/17 09:11 PM
. * Re: Update BrianT  11/27/17 01:02 AM
. * Re: Update AJR Hacker  11/27/17 03:03 AM
. * Re: Update Haze  11/27/17 01:11 AM
. * Re: Update Haze  11/27/17 07:45 PM
. * Re: Update SmitdoggAdministrator  11/27/17 01:05 AM
. * Re: Update Kitsune Sniper  11/26/17 09:19 PM
. * Re: Update AJR Hacker  11/26/17 11:15 PM
. * Re: Update Kitsune Sniper  11/26/17 11:33 PM
. * Re: Update Haze  11/27/17 12:11 AM
. * Re: Update Kitsune Sniper  11/27/17 12:27 AM

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