The beneficial legacy of the Commodore MAX Machine

The short-lived Commodore MAX Machine, aka Ultimax, aka VC-10, was a cost-reduced C64 with only 2k of user RAM, and no ROM at all:

(So, you needed a cartridge just to boot the machine: cartridge not included.)

In some sense it seems to be a predecessor of the C64, as we’re told the C64 cartridge port supports Ultimax mode, which is to say the cartridge is able to take over the entire memory space of the machine - and the unexpected benefit of that, to the user, is the possibility of freezer carts to take backups(!) and also unanticipated major hardware enhancement, like the present-day Ultimate line of cartridges for storage, network connectivity, software collections, realtime clock, memory expansion, and so on:

Most impressively perhaps, the back-in-the-day 20MHz SuperCPU:

Well, not really; the C64 did not exist at the time the MAX Machine came out.

Yes, it’s a bit confusing… the MAX has to be first, if the C64 is backward compatible with it. And yet it seems the C64 was very much an imminent product already, perhaps? (I did struggle with the wording, and missed that fix.)

Well, it’s pretty clear that the MAX Machine and the Commodore 64 share a huge amount of design. And there must have been a least a little bit of forward thinking going on there, since the MAX carts holding pin 8 low (which as far as I know makes no difference on the MAX) is what enables the G̅A̅M̅E̅ line on the C64.

The MAX was released in 1982-01 and the C64 eight months later, in 1982-08. Apparently the MAX was an independent design done in Japan. [max] Obviously some aspects of the design would be simiilar for any microcomputer designed around Commodore’s new chips, but being so similar as to be compatible seems to indicate a fair amount of co-ordination or re-use of the MAX design in the C64. It would be interesting to know just how this came about.

For freezer carts the key feature is actually to have N̅M̅I̅ (or possibly R̅E̅S̅E̅T̅̅) and a certain configuration of external memory available on the cartridge port; while G̅A̅M̅E̅ was certainly helpful here, it’s not clear to me that there might not have been other means to capture the flow of execution from an NMI had it not been there. So while I’ll agree that G̅A̅M̅E̅ was an important component in freezer carts, I wouldn’t go so far as to say that they couldn’t have been done if MAX compatibility mode hadn’t been included.

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