Snial
Well-known member
Well, that's an idea! One of the interesting things about a RISC CPU like the M88K is that JIT emulators should work well on ARM64 CPUs, because so many instructions have a 1:1 mapping. That's not the case in historical Mac CPU jumps as they've always been CISC to RISC or RISC to CISC where there's usually a 1:several instructions mapping. For example, 68K to PPC often involves multiple instructions to achieve a 68K addressing mode. And PPC to Intel often requires multiple instructions to handle PPC 3-operand instructions. And both kinds of emulation involve multiple instructions to handle flags (or the lack of them).I feel like with 3D printing and homebrew hardware being so affordable these days, that we could actually make functional versions of these design studies. Also ... that would have to be an 8 cm Mini-CD version of the CD 300, wouldn't it?
M88K to ARM64 is more straight-forward. And in this design, because it's earlier, mixed-mode execution is far more simplified, which means it's easier to handle too. You could probably get an SBC-based CPU to emulate an M88K (which in turn has its own Davidian-style 68K emulator) at 25MHz or 40MHz. A 400MHz ARM64 could do that (e.g. the latest Beaglebone or any R-PI, but I'd want a bare-metal emulator not running on top of Linux).
It'd also be interesting to develop a scaled down ADB styled keyboard, perhaps with keycaps and spacings matching the PB2400. Looking at my MBA M2 keyboard, it's a 63 key keyboard (because there's no function keys). But if one wanted to be even more radical, you could create a semi-chordal keyboard with far fewer keys. For example, 3x3 keys in the middle with 1x3 'shift' keys on the left + 1x3 'shift' keys on the right. Then, with 18 keys (and at least 6 shift options) you can generate at least (12*3*2)+15=87 key codes.