Recent content by Melkhior

One document that can be enlightening is the "Guide to the Macintosh® Family Hardware, Second Edition", which is available from vintageapple.com ; it describes a lot of the pre-'040 hardware. Alongside it is "Designing Cards and Drivers for the Macintosh Family, 3rd Edition"; with both of them...

Probably, but beware the behavior of MLCC capacitors. Voltage derating with DC bias can be really bad. Here's a cheap 50V, 100nF 0805 datasheet (JLCPCB 'basic' so great for cheap projects!): https://yageogroup.com/products/Capacitors/part/CC0805KRX7R9BB104 Select "Capacitance change vs. voltage...

Mmm, never looked at the serial port in details. But AFAIK, if you're lucky, they will all be in the same place in the memory space - they are all going to be the same hardware in any cases (or at least SW-compatible as they might have reimplemented some of the Z80C30 in their homegrown chip)...

Even limiting yourself to '040-based system, video can't be reliably determined, as Macs are perfectly fine when not using the onboard video (which is model-dependent) but a NuBus or PDS card instead. E.g., my Quadra 650 is perfectly happy with no internal video connected and my custom...

There might be a reason for that, beyond the fact people with '030 design would not have minded the non-multiplexed bus. Quoting the section 1.1.2 of the '040 UM: So any design using the multiplexed mode is stuck with full MC68040 @ 5V - no cheap LC option and no path to low-power static 3.3V...

@Oliver_A NeXT or Mac or most others, the hardest part will always be the software. Amiga didn't use the MMU (that I'm aware), and most of the software people wanted to run was compatible with the MC68000 so didn't use the new instructions in the MC68020 - upgrading to a '060 was "easy" SW-wise...

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...