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Interesting. True, I was thinking of how separate instruction/data contexts would have provided a sort-of 32MB address range (like the pdp-11). I knew it wasn't actually 31-bits, 1GB in the early 80s would have been even greater overkill. The Sun 3/60s we had access to at UEA, I think were...

I just wanted to read up on that again. http://www.bitsavers.org/pdf/sun/sun2/800-1185-01_2-120_CPU_Engr_Sep84.pdf In modern terms, a Context is like the ASID bits on a MIPS R3000: it allows multiple page tables to be present on the system and to switch between them by changing the context...

OK - compromise: on a 68000, you need contiguous memory at the CPU level :) ! Interesting. I suppose VISA means the "V8" memory controller chip, which contains a subset of the HMMU? I searched for the ROM listing, haven't found it yet. Yes, that's what I'm talking about. I think that it's...

Hi folks, So, I have tried to use the dosdude1 patcher and of course, it hangs because it has an AM28F010, which, as per this comment, needs 12V to program it. Gosh. I can't believe it's even possible to buy a flash chip that needs 12V any more and I had completely forgotten that the original...

That’s the important thing! Just wondering, what would stop it working on Panther? Is the OS that different?

I think I’ve figured out how an MMU can map discontiguous RAM at eg 64MB offsets and then run 24-bit mode System 6. It’s not too trivial, but this is how I’d do it. You set up 16MB worth of page tables (you only need 16MB/32kB=512 entries). To create the page table entries that map the rest of...

Pretty sure that the V8 memory controller on the LC and LCII make sure non-contiguous 4MB (or 2MB on the LC) and SIMM DRAM appear contiguous, because the LC has a 68020. It can’t use an MMU to do that. Also pretty sure the LCII ROM is almost exactly the same as the LC ROM and therefore doesn’t...

Throwing my weight of naivety and ignorance into the mix of this. My understanding is that for some Macs, particularly in the ≥68030 eras, but also going up to the PPC era (e.g. PowerBook 1400), non-contiguous RAM was handled both by custom chips and the MMU. But let's start with the Mac Plus...

Unexpected, since it has FireWire! I would expect so. Dazzle has to get the video data rate to somewhat below 12Mbits/s as it's a USB 1.1 device: pretty heavy compression. And I have the original installation CD! It's Mac OS 8.6 compatible! Wooh! Undoubtably! I do have a Canon MV500i DV...