lphillips@lpami.wimsey.bc.ca (Larry Phillips) (02/25/90)
In article <1827@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes: >I've heard that they take 2M out of the autoconfig space. > >Is this true? >Why? >Isn't the shared RAM only 128K? And doesn't the autoconfig protocol >provide for a minimum size of 64K? Unless there is something I'm missing >(quite likely), the Bridgeboards should only take 128K, not 2M. When was the last time you saw a 1 meg or 512K add-in board for a 2000? If it's going to use the memory address space, it effectively eats a 2 meg chunk in terms of real-world products anyway, even if it only needs 128K. -larry -- Gallium Arsenide is the technology of the future; always has been, always will be. +-----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca -or- uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 -or- 76703.4322@compuserve.com | +-----------------------------------------------------------------------+
blgardne@esunix.UUCP (Blaine Gardner) (02/25/90)
I don't own a Bridgeboard, but may need to get one in the future. I've
heard that they take 2M out of the autoconfig space.
Is this true?
For both the XT and the AT versions?
Why?
Isn't the shared RAM only 128K? And doesn't the autoconfig protocol
provide for a minimum size of 64K? Unless there is something I'm missing
(quite likely), the Bridgeboards should only take 128K, not 2M.
Does the Bridgeboard actually USE 2M of space (for a 640K computer?), or
was it just easier to build it this way?
--
Blaine Gardner @ Evans & Sutherland 580 Arapeen Drive, SLC, Utah 84108
Here: There: (My Amiga running uucp)
blgardne@esunix.UUCP blaine@worsel.UUCP
{decwrl, utah-cs}!esunix!blgardne utah-cs!caeco!i-core!worsel!blainenavas@cory.Berkeley.EDU (David C. Navas) (02/26/90)
In article <1827@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes: >I've heard that they take 2M out of the autoconfig space. > >Is this true? I have heard similarly. >Why? >Isn't the shared RAM only 128K? And doesn't the autoconfig protocol >provide for a minimum size of 64K? Unless there is something I'm missing >(quite likely), the Bridgeboards should only take 128K, not 2M. There are something like four modes of addressing the BridgeBoard. Remember that Intel structure ints are "backwords", that IBM bitmaps are interleaved, etc. The different modes of addressing are accomplished via using additional address lines, so you need at LEAST four times the autoconfig space. >Does the Bridgeboard actually USE 2M of space (for a 640K computer?), or >was it just easier to build it this way? My guess is that it was easier to build it this way... I would have rather had some global register settable to one of the four transfer modes -- but there is an efficiency cost/speed problem, as well as a re-entrant question. [Which might have been avoided with tc_Switch/tc_Launch, but oh well...] >-- >Blaine Gardner @ Evans & Sutherland 580 Arapeen Drive, SLC, Utah 84108 >Here: There: (My Amiga running uucp) >blgardne@esunix.UUCP blaine@worsel.UUCP >{decwrl, utah-cs}!esunix!blgardne utah-cs!caeco!i-core!worsel!blaine David Navas navas@cory.berkeley.edu "Think you can, think you can't -- either way it's true." Henry Ford
jms@tardis.Tymnet.COM (Joe Smith) (02/26/90)
In article <1827@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes: >I don't own a Bridgeboard, but may need to get one in the future. I've >heard that they take 2M out of the autoconfig space. >Isn't the shared RAM only 128K? And doesn't the autoconfig protocol >provide for a minimum size of 64K? Unless there is something I'm missing >(quite likely), the Bridgeboards should only take 128K, not 2M. The problem appears to be in that current memory expansion boards are 2M, 4M, or 8M, and must start on a 2M boundary. Which means that the smallest chunk of autoconfig addresses that can be allocated to a given board is 2M. When the Bridge Board gets 128K, the remaining 1920K is unusable. Too bad there isn't a way to make an Amiga memory board appear to the system as 3/4, 7/8, or 15/16 of its full size, so that the rest of the address space can be allocated to something else. (DEC did that with their smaller PDP-11 systems for years.) -- 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) (02/27/90)
In article <946@tardis.Tymnet.COM> jms@tardis.Tymnet.COM (Joe Smith) writes: >In article <1827@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes: >>I don't own a Bridgeboard, but may need to get one in the future. I've >>heard that they take 2M out of the autoconfig space. >>Isn't the shared RAM only 128K? And doesn't the autoconfig protocol >>provide for a minimum size of 64K? Unless there is something I'm missing >>(quite likely), the Bridgeboards should only take 128K, not 2M. Last I heard, BridgeBoards actually need 512K of memory. They only have 128K of actual shared RAM, but it's mapped differently at 0k, 128k, and 256k offsets from the configuration base. One mapping sends stuff straight through, one adjusts words from big to small endian ordering, and one mingles the bits of two words to make one longword (an operation called "skiggling" in a really weird computer language I once heard about), the idea being an assist to graphics translation from bitplanes to packed pixels. The final 128k chunk apparently has some I/O and control stuff in it. That's what they actually need; I have no idea if a BridgeCard actually requests 512K of space or it it's really asking for 2 megs. In the former case, you'd still be out of luck adding 8 megs of RAM, but 7 megs should work OK. >Too bad there isn't a way to make an Amiga memory board appear to the system >as 3/4, 7/8, or 15/16 of its full size, so that the rest of the address >space can be allocated to something else. (DEC did that with their smaller >PDP-11 systems for years.) It would be nice, but there's no way autoconfig can handle that; the memory grain a board responds to is pretty hardwired. Some memory boards can be set to subsets of their normal memory. But most 8 meg boards only support 2, 4, or 8 meg sizes (the ASDG design also does 6 megs). >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
blgardne@esunix.UUCP (Blaine Gardner) (02/27/90)
From article <1164@lpami.wimsey.bc.ca>, by lphillips@lpami.wimsey.bc.ca (Larry Phillips): > In article <1827@esunix.UUCP> blgardne@esunix.UUCP (Blaine Gardner) writes: >>I've heard that they take 2M out of the autoconfig space. >>Why? > > When was the last time you saw a 1 meg or 512K add-in board for a 2000? Well the ASDG 2M board sitting in my 2000 can handle .5M, 1M or 2M. :-) But I guess that's not the real point is it? It takes 2M whether it needs it or not. I guess the question I really should have been asking is why isn't that 128K mapped into the "other" autoconfig ($E00000) instead of our precious 8M of RAM space? Peripherials like drive controllers autoconfig in the $E00000 range, why not the Bridgeboard? -- Blaine Gardner @ Evans & Sutherland 580 Arapeen Drive, SLC, Utah 84108 Here: There: (My Amiga running uucp) blgardne@esunix.UUCP blaine@worsel.UUCP {decwrl, utah-cs}!esunix!blgardne utah-cs!caeco!i-core!worsel!blaine