I sat down and put some thought into this and this is just a wild guess.
CPU code names:
Apple’s first RISC project (based on the Motorola 88000 RISC): Jaguar, Tesseract
PowerPC 602: Galahad
PowerPC 603: Wart (King Arthur’s trusty aide) PowerPC 603e/603+/603ev: Stretch, Valiant PowerPC 603et: Goldeneye
PowerPC 604: Zephyr
PowerPC 604e: Helm Wind
, Sirocco, Twister PowerPC 604eq: Mach 5
Mac code names:
Power Mac 8600 and 9600
: Kansas, Montana
Mac code name:
Montana – Macintosh Classic IIMontana – Power Macintosh 7300
7600 – Power Macintosh 7600
^ I tend to trust Apple Confidential more than Wiki.
The case its in might
Your machine ID: 68
= 7600, 7500 (Machine ID for 8500/8550 is 69
Your case is physically dated: January 1996
Your CD drive is from: May 1996
Your CPU card is from roughly March 1996.
Your motherboard is from 1995.
So yours might have been put together in early 1996.
The 8500/8550 came out in late 1995. I think this rules out an 85XX proto unless they were planning really far ahead. Even then, why not use a motherboard from an 85XX series?
7600 came out in April 1996 = Could be 7600 proto. It originally had 604, but for a short bit did get a 200Mhz 604e. Could a dual 604e been planned ahead? I sorta doubt it and why the tower case? And this machine would have been put together just as the machine was released. Timing is not right.
9600 debut: Febr 1997 = Given that development time can take years and the dual CPUs did come out day one for the 9600...
Note: The machine ID of the 9600 is 67, the 8600 103 - even though they came out at the same time. Implies the 9600 was in development longer maybe? (Machine IDs are not always sequential) 8600 did not have dual CPU, 9600 did. Also the 9500 ID is 67 which is older of course. Why did Apple carry this ID over? The motherboard of the 9600 is very different than the 76/7500 or for that matter the 85XX but very similar to the 9500.
My conclusion, which is very much to be taken with a grain of salt:
The 9500, which debuted in May 1995 and was code named Tsunami, got dual 604e processor upgrades later in August of 1996 @ 180Mhz. So my guess is this machine was either a test bed for dual CPUs that ended up in the 9500 or its a very early concept for a 9600. Or both
. Keep in mine during this same time, the Manhattan/PowerExpress Manhattan project was going on. Those would be G3 projects. So development was going in 100 different directions. As for the code name Montana, I am sure that by the time this dual card was made, Montana (9600) was well into planning and development. It would be out in about a year but I bet no main logic board was finalized, but dual CPUs - probably green lit and planned. So Apple probably started developing dual CPU cards/software as part of the planning for the 9600 and for software developers to get early setups to develop on. And I bet this is why the 9500 also got dual CPUs late in the game, granted at a "reduced speed" as to not compete with the soon to be released 9600, but still to keep Apple ahead of the competition and sales revenue. Probably a push from marketing. Not to mention Apple could finally say they have a dual CPU system. That also means, unless I am forgetting something, this may be one of the very first dual processor setups Apple made!
In early 1996, no dual processor setup was sold by Apple yet.