jtb@dhw68k.cts.com (John Gibbons) (11/13/89)
Due to all the recent postings about Amix and the 2500UX, I was wondering if
it would be possible to run Amix (when it is released) on a stock amiga 2000.
Or at least a 3 meg 2000? I was under the impression that the reason this
wouldn't be the case is the lack of an MMU for the 2000. And as far as I know
the only way to get an MMU is to buy an A2620. This is a little too much
money for me to even consider, especially seeing the price of 32 bit ram.
Now of course cbm or even a third party source could come out with a MMU
only card (is this possible? I would imagine so, but you people know better).
This would allow the 2000 to run amix, assuming again, that the MMU is the
only thing standing in it's way.
So I would really apreciate it if someone could let me (and the rest of the
net) know the whole scoop.
One more thing, if it IS possible to run it on a 2000 with a hypothetical
MMU card, why not make one? Please? Pretty Please? etc..
Thanks..
--
John Gibbons
Internet: jtb@dhw68k.cts.com UUCP: ...{spsd,zardoz,felix}!dhw68k!jtb
//
\X/ "Amiga makes it possible!" "Atari. we almost did it right!" daveh@cbmvax.UUCP (Dave Haynie) (11/21/89)
in article <27562@dhw68k.cts.com>, jtb@dhw68k.cts.com (John Gibbons) says: > Due to all the recent postings about Amix and the 2500UX, I was wondering if > it would be possible to run Amix (when it is released) on a stock amiga 2000. > Or at least a 3 meg 2000? I was under the impression that the reason this > wouldn't be the case is the lack of an MMU for the 2000. Nope. It's not the memory, it's mainly, but not exclusively, the MMU. > Now of course cbm or even a third party source could come out with a MMU > only card (is this possible? I would imagine so, but you people know better). No, for several reasons. The MMU translates CPU addresses (logical) into memory or I/O addresses (physical). In order for it to achieve this feat of magic, it must sit in-between the CPU address bus and the rest of the system. So now you'll say "fine, why not just move my 68000 up on to this hypothetical MMU card". Second problem occurs here -- the MMU is a coprocessor device, like the FPU. So it responds to CPU space commands, which the 68000 can't generate. So in order to hook it up, you'd have to install it as a peripheral device, which would be pretty messy. Then you'd have to install some trapping software to emulate all the MMU instructions. And just when you thought you were working, along comes problem number 3 -- virtual memory. AMIX depends on demand paged virtual memory. The 68000 isn't capable of handling page faults -- it's bus error exception stack isn't large enough to support instruction restart or continuation. So you'd at least have to install a 68010. And finally, AMIX pretty much counts on a 68020 or 68030 I suspect (I am the hardware guy here, but I'm pretty familiar with what can go wrong with software on these things). It's not only 68020-specific instructions you have to worry about, but 68020-specific exception frames and other ugly things. Which brings you to the realization that you'd better have a 68020 or 68030 to run AMIX. You're also going to want it to run at a useful speed, which is another reason to want a fast 68020 or 68030. > John Gibbons -- Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Too much of everything is just enough