Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!sun-barr!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: RAMs for the A3000 Message-ID: <21893@cbmvax.commodore.com> Date: 24 May 91 16:48:37 GMT References: <1991May17.170845.8740@informatik.uni-erlangen.de> <21813@cbmvax.commodore.com> <1991May22.174606.30987@kuhub.cc.ukans.edu> Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 41 In article <1991May22.174606.30987@kuhub.cc.ukans.edu> markv@kuhub.cc.ukans.edu writes: >> First of all, there's no such thing as a "SIPP".The name refers to the part's >> physical configuration. >Yup, but I beg to differ. A SIMM of course is a little baby PC board >with RAM and an itty-bitty edge connector. SIPPs do exist, some PCs >use them. I have seen SIP parts in use before, of course. Like the Amiga video hybrid, Single In-line package. I haven't seen anything like that in RAM, but I don't spend much time with PClones either. SIMMs are apparently the most popular "add-it-yourself" form of memory; I've seen these on PClone, Macs, Suns, and even some Amiga add-on boards. >Also, Burst in general (on any machine) does not require SC parts, only the >3000 because of its design. That's absolutely true. With slightly faster memory and/or a faster clock to work with, we (Greg, actually) could probably have managed to support burst mode with page mode memories. >Other techniques (Interleaving, faster DRAMs, Nybble mode DRAMs, etc) can be >used to speed up DRAMs enough. SC of course is uniquely appropriate for >supporting bursting in particular. Actually, Nybble-mode memories are the most "natural" at supporting burst cycles, since the 68030 burst cycle is essentially the same kind of cycle as a DRAM's nybble-mode. Burst mode starts with a address for the first longword, but the next three use an assumed address that are sequential, MOD 4, from this base address. Nybble-mode memory works just the same way. Static column, on the other hand, requires an exact address for every word, which the RAMSEY chip creates. However, you need more nybble-mode (because it's generally only in "x1" packages) or interleaved memory (because it counts on banks) to support burst, while using a smart RAM controller and static column (or page mode, if the timing worked out), you can get by with only a single bank. No DRAM is fast enough to support 68030 burst at 25MHz without some kind of special mode or interleave techniques. -- 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.