jms@tardis.Tymnet.COM (Joe Smith) (02/13/90)
A question for Dave Haynie or other hardware types at CATS.
Now that I have installed the 1-meg Agnus, nothing is using the address
range at $C00000. Does the design of the BridgeBoard allow the shared
memory to appear at other than the auto-config range? In particular,
is it possible to have 1-meg of CHIP RAM, 8-megs of fast RAM, and run
the BridgeBoard at $C00000, all at the same time?
Is it feasable to change the address decode logic on the A2286 if it does
not support this?
--
Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com
BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms
PO Box 49019, MS-C41 | PDP-10 support: My car's license plate is "POPJ P,"
San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga speaks for me."daveh@cbmvax.commodore.com (Dave Haynie) (02/14/90)
In article <931@tardis.Tymnet.COM> jms@tardis.Tymnet.COM (Joe Smith) writes: >A question for Dave Haynie or other hardware types at CATS. >Now that I have installed the 1-meg Agnus, nothing is using the address >range at $C00000. Does the design of the BridgeBoard allow the shared >memory to appear at other than the auto-config range? In particular, >is it possible to have 1-meg of CHIP RAM, 8-megs of fast RAM, and run >the BridgeBoard at $C00000, all at the same time? No, the Bridge Board memory will always be autoconfigured. It is impossible to reliably locate any expansion card at $00C00000, because even if you were to hack it to do so physically, the OVR* signal you'd also have to hack isn't fast enough from the expansion bus on an A2000 to cause the extra memory to overlay the $00C00000 memory. And that overlaying feature won't even be there in the future. Second thing is, only 128K of Bridge Board memory is shared between the Bridge and the Amiga Bus, so you'd be wasting a great deal of effort for only a little extra memory. >Is it feasable to change the address decode logic on the A2286 if it does >not support this? You'd have to hack the configuration latch on the A2286 to force the "C0" address. Then cut away the SLAVE* signal, so the card wouldn't register a bus collision ($00C00000 space is reserved motherboard space, not expansion bus space). The memory couldn't be DMAed to, since the system would expect it to be on the motherboard and turn on the bus buffers at the wrong time. And it wouldn't work on the A3000. I'd recommend against it. >Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com -- 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
jms@tardis.Tymnet.COM (Joe Smith) (02/23/90)
In article <9663@cbmvax.commodore.com> daveh@cbmvax.cbm.commodore.com (Dave Haynie) writes: >In article <931@tardis.Tymnet.COM> jms@tardis.Tymnet.COM (Joe Smith) writes: >>is it possible to have 1-meg of CHIP RAM, 8-megs of fast RAM, and run >>the BridgeBoard at $C00000, all at the same time? > >No, the Bridge Board memory will always be autoconfigured. >Second thing is, only 128K of Bridge Board memory is shared between the Bridge >and the Amiga Bus, so you'd be wasting a great deal of effort for only a >little extra memory. I would not call 4 megabytes "only a little memory". I am refering to the instructions on the A2058, which say that if you have a fully populated board with 8 megabytes of expansion RAM and want to run a Bridge Board, you have to change the jumper so that the memory board uses only 4 megabytes. Several hundred dollars of memory chips suddenly made unuseable. That's what bugs me the most about the current implementation of the Bridge Board plus Commodore memory boards. The interaction of the two wastes a lot of the address space. -- Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-C41 | PDP-10 support: My car's license plate is "POPJ P," San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga speaks for me."