Radius Rocket disabled MMU... anyone knows why?

[GeekDot]

Hey gang,

After many moons of waiting on my todo-stack, I finally repaired my Radius Rocket. Runs fine and all...

..but there's one strange thing I came about when doing nastier things than running MacBench: It claims not having an MMU (while the installed 68040/25 certainly has one) - the 'mmu ' Gestalt return-code is empty.

I'm not the first one stumbling across this, like this guy in 1999... and it looks like there are some more 040 accelerators not providing MMU functionality.

A quick measurement showed they're asserting /MDIS ("MMU disable", pin S6, pulled high)... anybody every heard why they did that? 

I was under the impression that a Rocket is a completely "sandboxed" Q9x0 minus I/O and own bus.

 

[Trash80toHP_Mini]

That is a strange one. With full RAM loadout support on board, PMMU might not have been required a/o interfered with Appletalk over NuBus? Since it was intended for use in multiples along with the Host board under RocketShare. I'm not sure where paged memory might be supported, but I can imagine any number of ways support might bomb the system.

The accelerators listed in you link would likely have similar conflicts?

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From the RAMDoubler 1.6.2A Updater Read Me:

Accelerators that do not support Apple's Virtual Memory are not compatible with RAM Doubler.  These accelerators which lack a MMU (M=emory Management Unit) include:
- Radius Rocket
- Fusion Data System's TokaMac
- Mobius Speedster 040
- Applied Engineering Transwarp
- MicroMac Carrera

Similarly, non-accelerator hardware add-ons that are not compatible with Apple virtual memory may have problems with RAM Doubler as =
well; all third-party PowerBook display cards, notably the Envisio display adapters, are not compatible with RAM Doubler.

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