From: Bil Herd (bherd_at_idsbusiness.com)
Date: 2008-11-28 17:25:24
Yep, a goodly number of cartridges were Max cartridges. Freddy Bowen used to keep a generic cartridge (cant remember if it had a zif socket or not) and a grabber hook type jumper cable for grounding the /GAME line. That was actually the first piece of C64 technology I witnessed my first week when he popped the cover and grounded the line.
That line was in part responsible for the Z80 in the C128, every cartridge up until the Magic Voice had either a hard ground or no ground, what the MV did was to detect the reset vector of the 6502 and ground the /GAME line on the fly and substitute it's own reset vector (and probably interrupt vectors as well). It was a clever way of having the first say but unfortunately the MV cartridge knew nothing about how to set up the MMU and switch to C64 mode. Since the Z80 would boot from $0000 it would take a look at the cartridge "safely" and initialize to C64 mode and then take a flying fling at the reset vector.
Cant remember the CIA's, I'd have to look at a schematic.
Quiz: What Japanese engineer is most associated with the Max or Game machine?
Bil
-----Original Message-----
From: owner-cbm-hackers@ling.gu.se [mailto:owner-cbm-hackers@ling.gu.se] On Behalf Of Marko Mäkelä
Sent: Friday, November 28, 2008 7:32 AM
To: cbm-hackers@ling.gu.se
Subject: Re: UltiMax schematics
Bil,
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?
Marko
>
> Bil
>
> -----Original Message-----
> From: owner-cbm-hackers@ling.gu.se [mailto:owner-cbm-hackers@ling.gu.se] On Behalf Of Marko Mäkelä
> Sent: Friday, November 28, 2008 3:16 AM
> To: cbm-hackers@ling.gu.se
> Subject: Re: UltiMax schematics
>
> On Fri, Nov 28, 2008 at 08:27:18AM +0100, ruud.baltissen@apg.nl 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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>
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>
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