Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!clyde.concordia.ca!nstn.ns.ca!news.cs.indiana.edu!samsung!usc!sdd.hp.com!wuarchive!ukma!psuvax1!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: 32 bit memory??? Keywords: 32 bit memory is there really a difference???? Message-ID: <19109@cbmvax.commodore.com> Date: 19 Feb 91 14:34:46 GMT References: Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 34 In article undrground!bryanh@amix.commodore.com (Bryan Harpel) writes: >> the special chips, but you Really Want 32-bit for other ram if you have >> higher than 68000 cpu. There is an important difference here. > I am about to buy 32 bit ram for my GVP Accel. board. I was curious >about 1 thing, I can only afford to get the 2 meg version as of now. >Will it run slower than if I got the 4 meg version, or is two megs of 32 >bit enough to help out the 68030's BURST mode? That depends completely on the GVP's design. Some designs require 4 MB chunks to support burst mode, others work in smaller chunks, like the A3000's memory system. This depends on the kind of memories, the size of memories, etc. Unless anyone around here specifically knows the GVP memory board's specifics, your best bet would be to call GVP. Using memory chips, it works out something like this. There are three kinds of "special" memory modes which can be used to support burst mode: page mode, static column mode, and nybble mode DRAMs. Nybble mode looks just like the 68030 burst mode, so it hooks up with practically no extra "magic". However, at least when I was working on the A2630, you could only get nybble mode parts in 1 bit packages. So, for a 32 bit bus, the minimum "bank" of memory would come out at 4MB, but we had to support 2MB. So no burst. On the A3000, we use static column memories to run burst mode. Static column and page mode memories are very similar in many respects, especially in the fact that they don't naturally support burst mode. So you need additional, fast logic to get them to coexist with burst mode. The high integration of the A3000's memory controller made this a reasonable thing to do. >Bryan Harpel -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "What works for me might work for you" -Jimmy Buffett