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Any vintage Apple buffs that can explain the ARM logo on this Macintosh Processor Upgrade Card (PowerPC 601 PowerMac, circa 1994)? I know Apple & VLSI were seed investors in ARM. Do old PowerPC chipsets have an embedded management core? mastodon.social/media/6DXjn70N

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@projectgus That looks like a NuBus card - possibly an upgrade card for an older 68k Mac? Then it's probably more something like some custom glue logic thing, and not a CPU in whichever form.

@galaxis it is indeed for upgrading a 68k Mac to a PowerPC. You're probably right, I'm just wondering why it has an ARM logo on it.

An earlier prototype has much the same chips, but no big ARM logo.

archive.org/stream/MacWorld_94

I think VLSI were the first ARM licensee - there could be an ARM in there, and given the label, I think there must be. Perhaps needed to setup the board for the PPC to boot.

@galaxis @projectgus

@EdS @galaxis Nice find!

Doing some kind of early boot configuration sounds plausible to me.

@projectgus @EdS According to web.archive.org/web/2002081715 it was possible to switch between the PPC and the m68k CPU with a reboot, so there must have been some pre-boot toggle to decide which CPU to power up - can't have been both on the bus.
The MacWorld image designates the chip as "040 bus adapter and cache controller", which sounds plausible (the card seems to have brought a Mac PPC ROM, but had to talk to memory and periphereals over the 68040 CPU bus).

@galaxis @EdS Good thinking.

My understanding is you could run a software tool in Mac OS to change it, which I'm guessing flips a bit in some non-volatile storage somewhere. I noticed the ROM stage of the Mac double-reboots (two chimes) the first time after installing or removing the card...

@galaxis @EdS I do, although I was found this cleaning it up to sell it as I couldn't think for a use for it...

It is tempting (albeit super fiddly) to change plans and try to poke around inside of it instead, though...

From Twitter comes a few clues:

Apple not the designer for these, Daystar.

A "real" PowerMac 6100 of the same era has no VLSI chips at all. images.esellerpro.com/2131/I/5

Similar era 68K Macs have lots of VLSI chips but nothing marked ARM.