I think the OP said this was in a Centris 650. Didn't the Centris have a 25MHz bus? The Quadras were pretty much identical to the Centrises but with a 20 to 25 MHz bump for the 610 and a 25 to 33 bump for the 650.Actually, interesting point here: I don't see a crystal on that board, and the board was in a Q650. The PDS slot in that machine is going to be running at 33mhz.
Again, totally not going to rule out it being an '040 acellerator, but it's a very weird one if that's what it is.
Yep, according to Everymac.com, the Centris 650 has a 25MHz bus/CPU and the Quadra 650 has a 33 MHz bus/CPU. So this could be an early clock doubling CPU upgrade, but I agree with Gorgonops, it would be worth at least turning it over and counting the pins. Also, check along the top edge of the heat sink.
The 68040 has its part number printed on the top edge and often, folks would attach the heat sink so as to leave that labeling visible.
As to whether a PDS CPU upgrade **needs** an extension/control panel or not, I had a conversation in which I was told that one of the early daughter board upgrades on the 128K/512K used some trick in bus arbitration to shut down the host CPU, but in that case, the upgrade has full access to all of the original CPU's pins. So I could go either way. Sure seems like the Turbo040 and such are active whether you load Daystar's software or not, but my memories are old and crumbly.
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