markv@kuhub.cc.ukans.edu (04/01/91)
In article <19620015@hp-lsd.COS.HP.COM>, davem@hp-lsd.COS.HP.COM (Dave K. Martin) writes: > I had posted this in c.s.a.emulations and haven't recieved any responses and > on reflection, it appears to be more hardware oriented, so here it is again. > > Why is 6-meg of fast ram the ideal configuration for an A-2000 with a > bridgeboard? Does it have to do with address conflicts on the Zorro buss > and the shared memory on the bridgeboard? The Bridgeboard grabs 2MB of Zorro II autoconfig space for itself. So if you have 8MB of fast RAM, you will have a conflict with the BB. >I'm asking since my A-2000 now has 6-meg of fast, 1-meg chip and an XT bridge. >What happens if I get another 2-megs of fast ram? Nothing? System slowdowns? > Frequent visits from the Guru? It depends I think. Depending on which board is in which slot (which affects the order the cards autoconfig in), you'll either get NO BB (because the RAM board has aready taken the whole address space, so the BB's autoconfig fails), or you get no RAM or 6MB RAM (not sure which, I think it depends on the board but I'm not a real autoconfig guru). With the 3000 or GVPs new cards, you can get RAM that autoconfigs outside the Zorro II space, so you don't have the 8MB space limit. > > thanks..... > > davem -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Mark Gooderum Only... \ Good Cheer !!! Academic Computing Services /// \___________________________ University of Kansas /// /| __ _ Bix: mgooderum \\\ /// /__| |\/| | | _ /_\ makes it Bitnet: MARKV@UKANVAX \/\/ / | | | | |__| / \ possible... Internet: markv@kuhub.cc.ukans.edu ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
dltaylor@cns.SanDiego.NCR.COM (Dan Taylor) (04/02/91)
In <19620015@hp-lsd.COS.HP.COM> davem@hp-lsd.COS.HP.COM (Dave K. Martin) writes: >Why is 6-meg of fast ram the ideal configuration for an A-2000 with a >bridgeboard? The BB shared memory is 1/2 Meg. You can have more than 6-meg, but compensating for that 1/2 Meg is tough. I suppose an A2091, with 1Meg, and a second with 1/2 Meg would do it ;-). Actually, I haven't been able to find out if the disk interface on the A2091 takes up ANY expansion space, although I'm sure the RAM on it will. Anyway, the 6-Meg number comes from the difficulty of find 1-1/2 meg expansion RAM. What happens if you overstuff the expansion space, is that the overflow devices, whichever they are, are ignored. Dan Taylor
daveh@cbmvax.commodore.com (Dave Haynie) (04/02/91)
In article <19620015@hp-lsd.COS.HP.COM> davem@hp-lsd.COS.HP.COM (Dave K. Martin) writes: >Why is 6-meg of fast ram the ideal configuration for an A-2000 with a >bridgeboard? It's the most autoconfig memory you can easily use on an A2000 and still have a bridgeboard installed. >Does it have to do with address conflicts on the Zorro buss and the shared >memory on the bridgeboard? ^^^^ That's "bus"; "Buss" is a fuse company, "buss" is what our grandparents did on dates, like "spooning"... The Zorro II implementation on the A2000 supports a total of 8.4MB of expansion space, divided up into an 8MB chunk and a 488K chunk. BridgeBoards require 512K of space, leaving 7.5MB of space left in the 8MB chunk. 6MB is the closest approximation to 7.5MB that makes sense to most designers. One of the problems is that autoconfiguration units can only be in powers of 2, between 64K and 8MB. So to get 4MB or 8MB, you only need one autoconfig unit. To get 6MB, you need two, and to get 7.5MB, you would need four. Each new autoconfig unit is extra hardware complexity, and as far as memory goes, each new one would get you less and less additional benefit. >What happens if I get another 2-megs of fast ram? You run out of configuration space. The last card in your system doesn't get configured. >davem -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "That's me in the corner, that's me in the spotlight" -R.E.M.
peterk@cbmger.UUCP (Peter Kittel GERMANY) (04/03/91)
In article <19620015@hp-lsd.COS.HP.COM> davem@hp-lsd.COS.HP.COM (Dave K. Martin) writes: > >Why is 6-meg of fast ram the ideal configuration for an A-2000 with a >bridgeboard? Does it have to do with address conflicts on the Zorro buss >and the shared memory on the bridgeboard? > >I'm asking since my A-2000 now has 6-meg of fast, 1-meg chip and an XT bridge. >What happens if I get another 2-megs of fast ram? Nothing? System slowdowns? >Frequent visits from the Guru? (Perhaps this should get included in the FAQs, so once again:) There is only one 8-MB address space to be distributed among all those autoconfig devices. If you spend all that space already for RAM, there is no room for further additions. A bridgeboard reserves 512 KB of autoconfig space, so it wouldn't fit in anymore. You wouldn't encounter an error, the BB simply would stay quiet, you *NEVER* could bring it to life! -- Best regards, Dr. Peter Kittel // E-Mail to \\ Only my personal opinions... Commodore Frankfurt, Germany \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk