Re: UltiMax schematics

From: Marko Mäkelä (
Date: 2008-11-28 13:32:02


On Fri, Nov 28, 2008 at 06:58:08AM -0500, Bil Herd wrote:
> Yes, the C64 and C128 have a 'max mode where most of the resources
> like memory and ROM are disabled.

Right, everyone here should know that asserting -GAME enables the Ultimax
mode, where only the I/O chips and the low 4k RAM are mapped and the
upper 8k addresses are mapped to -ROMH.

What I meant to say is that if the "CIA" and "CIA PLA" lines are to be
shorted on Max cartridges, it should be safe to short the corresponding
lines in the C64 cartridge port as well.  Is this the case?

I seem to remember that some early 8k game cartridges from Commodore Japan
are actually Ultimax cartridges.  If memory serves, these would include
Gorf, Slalom, Jupiter Lander, and Radar Rat Race.  (Most or all were likely
ported from VIC-20.)  Can you confirm any of this, Bil?


> Bil
> -----Original Message-----
> From: [] On Behalf Of Marko Mäkelä
> Sent: Friday, November 28, 2008 3:16 AM
> To:
> Subject: Re: UltiMax schematics
> On Fri, Nov 28, 2008 at 08:27:18AM +0100, wrote:
> > Sorry, no offence meant. But AFAIK it is the first time I encountered a
> > computer where some internal logic is activated by inserting a
> > cartridge.
> If homebrew counts and if your definition of "internal logic" covers GPIO,
> I have an example: Someone hacked an Atari VCS 2600 to contain a number of
> games built-in.  If no cartridge was inserted, you'd choose from the
> built-in games.  Cartridges were detected by cutting one of the ground
> contacts on the connector.  All known cartridges would connect all ground
> contacts together.  If no cartridge is inserted, the cut ground contact
> would be floating (or pulled up by a resistor).
> That said, I'd like to see evidence too.  Shouldn't the known UltiMax
> game cartridges work on a regular C64 as well?
> 	Marko
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