A pair of 25Mhz Motorola 68NC040 processors. While the 68LC040 lacked an inbuilt FPU and the 68EC040 lacked both FPU and MMU, the 68NC040 lacked FPU, MMU, and CPU to come in as the cheapest 25Mhz processor on the market in 1991.
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i got to tinker with one of these once, and while its original low cost makes it historically interesting, unfortunately Mac OS always had compatibility issues when run without a CPU, so i'd recommend upgrading it if you get a vintage Mac with an NC installed
What the hell were Moto engineers thinking here? The lengths that OEMs had to go through to make heat sink solutions for this chip was ridiculous and most of them wound up overheating. Ugh.
I had to do some googling to find out what the one in the picture was for. It was a terminator for multi-cpu systems. I was like where the hell is the die in that thing.
If you wrap some wire around and sew in a ferrite bead, you can activate the Core Cache mod. It proved not very popular back then because it was destroyed once it was read from
Later these would be sold as NPUs (No Op Processing Units). Adding a nop accelerator allowed the 68040 to offload nop processing allowing it to do nothing far faster than an unaccelerated Mac
intel sold what literally amounted to this as part of the RapidCAD 386 -> 486 upgrade, it included a dummy FPU for the 386's FPU socket to just sit there and return that a FPU was present. the actual FPU was part of the main CPU package.
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engr 2: [looks at coconut donut in his hand] "oh! I know!"
Bad news! You think this is a joke (it is), but check out what an Intel 80487 actually was: https://en.wikipedia.org/wiki/X87#80487