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Never realized they had done that - from the '040 timing diagrams, it doesn't seem to cost anything in performance though a lot of external hardware will need to capture the address rather than just use the live version as in non-multiplexed mode... this could add quite a bit of hardware, though...

All the 80s 68k workstations were built to be the fastest 68k machines. The personal computers (Mac, Amiga, ST, QL, whatever) were the ones built to be cheap. Workstation vendors were all looking for low latency memory, DMA everywhere, etc. My personal favorite, Sun, did have a 0-latency MMU for...

Agreed. The MC68060 is nice and all, but the lack of some integer instructions is a problem for old codes. The support package is nice, but unlike the FPU support package, the performance impact is significant [1]. A nice soft-core in a FPGA would be a great thing to have. But... The only...

To verify you do have a problem, you can take a pointer to the FP value, cast it to something integer, and then display as hex. Then you can compare the hex values between implementation. One issue will be which FP you use. FP32 and FP64 are supposed to be IEEE-compliant but rounding might...

It's possible - I just don't know of any implementation doing it in "normal use". As I mentioned, Sun-2/3's "boot mode" sort-of does it, but in practice it's not really separate address spaces as there's no "overlap": the PROM always use the addresses from when it's mapped by the MMU, it's just...

It's a feature of the reference MMU defined with SPARC V8; V7 systems (sun4, sun4c) only use variants of the Sun-style MMU (inherited from the suN1, sun2 and sun3), while V8 systems (sun4m, sun4d) use a more conventional MMU and a hardware page walker. And for completeness, the offshoots: sun3x...

Not in "normal" use, but sort-of in "boot" mode. When the PROM first starts running on a Sun-2/3, a bit in a hardware register is set to "boot mode". While this bit is set, FC=6 accesses (Supervisor Program) are directed to the PROM itself, rather than memory. The Sun-2/3 can't bypass the MMU...

Which is neat. But Sun must have realized it was a bit overkill in the Sun-2 implementation which you look at; in the Sun-3, the two fields (Supervisor and User) were removed to have only one for both. They also simplified the permission bit a lot, going from 6 to 3 (if you count valid). They...

Normally, JLCPCB needs the gerber files (to make the PCB), a BOM (bill of material, the list of components you need), and a placement file (so the pick-and-place machine places the components in the right place for soldering). In my repo, the required files for the PCB should be in IIci_ATX.zip...

At the time (Feb'23), the command history says $24.75 for 5 populated boards, including custom/duties to France. No memory how that translated into euros at the time. Yes, they did all the SMD stuff (passives, the gate, the small switch), I bought the actual connectors for both sides from...

Adapter: depending on where you live, might be faster/cheaper to just make your own. My version is here; other people have rolled out different solutions. Mine is mostly SMD (had them done by JLCPCB), I soldered the two connectors by hand (There's a picture). It has a power-good led and a small...

First, my bad, should have written "68000" in the paragraph you answer to, not "68k". Though my point (you need contiguous memory at the hardware level) also apply to fully MMU-less 68020 (from the '030 onward, the MMU is used). As for the LC and LCII, the easiest way it to quote Apple's...

Pretty sure it's not the case for the 68k based systems. Non-contiguous addresses visible from software is a massive pain (as all those who tried to increase the amount of memory in those old systems quickly find out). Much easier to make memory contiguous in hardware. ... so the memory *is*...

IIRC, RAM Doubler required a MMU. You can do a lot more magic when you have a MMU :-)

The Plus (and all those using 68000, plus the MMU-less II and the original LC) don't deal with non-contiguous memory very well because they expose the physical address of the hardware directly to the software. In theory, you could use discontinuous area for RAM, but allocating and deallocating...

Not quite the same use case, but might be helpful anyway: I never found pins to expand a socket on the usual sites, but I did find some on AliExpress. I was looking to convert a '040 PGA socket (available on Mouser) from regular to V (they have another 3 pins, the socket is unobtainium). A...

Not in the OS Open Firmware is designed to be embedded in the machine itself (in ROM, Flash, whatever) to initialize the machine hardware and then be able to boot it into an operating system - it runs before the OS. Some (most) of that stuff is in actual binary machine code (PowerPC for Apple...

It's an open standard for a boot system, namely IEEE 1275. It was originally developed by Sun as OpenBoot for their own systems when they introduced SPARC (as a replacement for the 68k used in previous systems). It has nothing to do with PCI originally, as the first systems with OpenBoot were...

Just to avoid searching for the wrong thing: the IMS G300 isn't a transputer, it's a "Color Video Controller" (read: video DAC) and would have made a high-resolution device (max 1280x1024 for some). It was made (designed, rather) by INMOS, and manufacturd by SGS Thomson. So don't expect...

Still the best reference. The thing to understand - and that is far from obvious - is that pipelining is expensive in area. Whenever a pipeline stage is cut in half to boost frequency, it means that all signals have to be registered in the middle (the value of the signal has to be captured into...