CRONEJP@UREGINA1.BITNET (Jonathan Crone) (03/23/88)
With all the recent talk about the new amiga models and the discussion of
the 68020/68881 board from Commodore the same question keeps coming
to mind.
What happens to the A2000's 68000 when the 68020 goes in?
I know that the logic on the 86pin connector provides for the coprocessor
board to steal the system from the 68000 (I think thats right isn't it??)
but does the 68020 run everything in the system or is the
68000 run as a I/O processor like in some maxi-desktop systems that i've
seen running un*x???
does it not make sense to have the 68000 operating in this fashion????
after all if you're to be running AMIUNX <------- My nomination for the
name of the new unix...
it doesn't make sense to have the 68020 waiting on I/O
so why not have the 68000 as a I/O hound or something....
(I know that with the current Amiga O/S the 68000 isn't stuck waiting on
I/O but with two 68XXX 's under the hood the A2500 could sure make the
MacII look like a slug.
This of course is just my opinion....
jpc
====================================================================
Jonathan P. Crone
Vice President, AURA, (Amiga Users of Regina Associated.)
(Regina, Sask. Canada ) (eh???)
CRONEJP@UREGINA1.BITNET
....rutgers!mimsy!uunet!mcl!cronejp
come on now.... does ANYONE give a damn about what i have to say?
====================================================================CRONEJP@UREGINA1.BITNET (Jonathan Crone) (03/23/88)
With all the recent talk about the new amiga models and the discussion of
the 68020/68881 board from Commodore the same question keeps coming
to mind.
What happens to the A2000's 68000 when the 68020 goes in?
I know that the logic on the 86pin connector provides for the coprocessor
board to steal the system from the 68000 (I think thats right isn't it??)
but does the 68020 run everything in the system or is the
68000 run as a I/O processor like in some maxi-desktop systems that i've
seen running un*x???
does it not make sense to have the 68000 operating in this fashion????
after all if you're to be running AMIUNX <------- My nominaaion for the
name of the new unix...
it doesn't make sense to have the 68020 waiting on I/O
so why not have the 68000 as a I/O hound or something....
(I know that with the current Amiga O/S the 68000 isn't stuck waiting on
I/O but with two 68XXX 's under the hood the A2500 could sure make the
MacII look like a slug.
This of course is just my opinion....
jpc
====================================================================
Jonathan P. Crone
Vice President, AURA, (Amiga Users of Regina Associated.)
(Regina, Sask. Canada ) (eh???)
CRONEJP@UREGINA1.BITNET
....rutgers!mimsy!uunet!mcl!cronejp
come on now.... does ANYONE give a damn about what i have to say?
====================================================================lel@wuphys.UUCP (Lyle E. Levine) (03/24/88)
In article <8803222026.AA06299@jade.berkeley.edu> CRONEJP@UREGINA1.BITNET (Jonathan Crone) writes: > >What happens to the A2000's 68000 when the 68020 goes in? >I know that the logic on the 86pin connector provides for the coprocessor >board to steal the system from the 68000 (I think thats right isn't it??) > >but does the 68020 run everything in the system or is the >68000 run as a I/O processor like in some maxi-desktop systems that i've >seen running un*x??? The system will be controlled by EITHER the 68000 or the 68020. Period. To change this (I believe) would entail a large redesign of both the 2620 board, and the Amiga motherboard. As I recall, Andy once mentioned that you can disable the 2620 at boot time to allow one to use just the 68000 if desired. This was a VERY GOOD IDEA!!! Thanks Commodore! (This is still true,... isn't it?....) >I/O but with two 68XXX 's under the hood the A2500 could sure make the >MacII look like a slug. What with the MAC II's sluggish OS and lack of the Amiga's custom chip set, I'd bet on the amiga anyway! Also, the 68881 is asynchronus, so you should be able to use a 25MHz chip (independent clock Andy?) for the math coprocessor. >This of course is just my opinion.... > > >jpc > >==================================================================== >Jonathan P. Crone ^^^^^^^^^^^^^^^^^ Before our site got it's posting fixed, I got a letter from someone about a plotting program of mine. Was that from you? As I recall, our mailer was also fritzed and I couldn't respond. Your name sounds familiar. ========== IBM is a Division of Sirius Cybernetics Corporation "their fundamental design flaws are completely hidden by their superficial design flaws." - "So Long And Thanks For All The Fish" Lyle Levine: Paths -> ihnp4!wuphys!lel uunet!wucs!wuphys!lel
daveh@cbmvax.UUCP (Dave Haynie) (03/25/88)
in article <8803222026.AA06299@jade.berkeley.edu>, CRONEJP@UREGINA1.BITNET (Jonathan Crone) says: > What happens to the A2000's 68000 when the 68020 goes in? Good question! > I know that the logic on the 86pin connector provides for the coprocessor > board to steal the system from the 68000 (I think thats right isn't it??) It's not really stealing. The Coprocessor card asks the 68000 for the bus, via a signal called Bus Request. A bit later, the 68000 responds with a signal called Bus Grant, which is basically saying, "I'm cool, just wait for the end of this cycle". This is really the same way all 68000 DMA works. At the end of this cycle, the 68000 protocol says that you assert a signal called Bus Grant Acknowledge, and remove your Bus Request. This is something that the Coprocessor card could do, and is in fact what all the expansion bus DMA devices do. Such DMA device will be in charge of the system until it drops Bus Grant Acknowledge, at which point the 68000 or another DMA device may get the bus. The trick is that, while Bus Grant Acknowledge is active, no other card can get the bus. So if your CPU slot card took the bus that way, no other DMA could take place. On the CPU bus there's another acknowledge signal, called BOSS. If a CPU card activates that signal, it shuts only the 68000 off. The Bus Grant from the expansion bus now goes to the CPU card's Bus Grant line, and the CPU card's Bus Grant line is now an input to the expansion bus arbitation logic. So hard disks and things can request the bus from the 68020 or whatever you've got installed in there. > but does the 68020 run everything in the system or is the > 68000 run as a I/O processor like in some maxi-desktop systems that i've > seen running un*x??? With the A2620 card, we let you kick the 68000 back in on system reset, for testing software and things, but you can't dynamically switch it. The motherboard logic supports dynamic switching between the two, so it would be possible to design a card that let both CPUs run at the same time. That's more complicated, and we didn't really have room for it in the current 68020 board design. > does it not make sense to have the 68000 operating in this fashion???? > after all if you're to be running AMIUNX <------- My nomination for the > name of the new unix... It might make sense, if you could keep the 68020 on it's board most of the time. If it had to go offboard to talk to any motherboard resources very often, it could actually be a loss, since arbitrating between the two busses does take a finite amount of time. > it doesn't make sense to have the 68020 waiting on I/O > so why not have the 68000 as a I/O hound or something.... No one's waiting on I/O around here, bud! We're interrupt and DMA driven, so you only go service the I/O when there's something there to service, at least for the most part. While one tasks "waits" for I/O, the CPU's off doing something else, if there's anything else useful to do. > (I know that with the current Amiga O/S the 68000 isn't stuck waiting on > I/O but with two 68XXX 's under the hood the A2500 could sure make the > MacII look like a slug. That's OK, we intend to anyway. Though I will admit I think the Mac II has a neater case. > This of course is just my opinion.... > jpc > Jonathan P. Crone -- Dave Haynie "The B2000 Guy" Commodore-Amiga "The Crew That Never Rests" {ihnp4|uunet|rutgers}!cbmvax!daveh PLINK: D-DAVE H BIX: hazy "I can't relax, 'cause I'm a Boinger!"
daveh@cbmvax.UUCP (Dave Haynie) (03/26/88)
in article <525@wuphys.UUCP>, lel@wuphys.UUCP (Lyle E. Levine) says: > What with the MAC II's sluggish OS and lack of the Amiga's custom chip > set, I'd bet on the amiga anyway! Also, the 68881 is asynchronus, so > you should be able to use a 25MHz chip (independent clock Andy?) for > the math coprocessor. There's a spot on the A2620 board for a clock module that goes into the 68881/68882 clock input. So you can run it however fast your math chip can handle it. I've got a 68881 running at 25Mhz in the lab as we speak, the other one was in the system on the display floor at CeBit, though it didn't really do any math with it. > Lyle Levine: Paths -> ihnp4!wuphys!lel > uunet!wucs!wuphys!lel -- Dave Haynie "The B2000 Guy" Commodore-Amiga "The Crew That Never Rests" {ihnp4|uunet|rutgers}!cbmvax!daveh PLINK: D-DAVE H BIX: hazy "I can't relax, 'cause I'm a Boinger!"