Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!spool.mu.edu!samsung!zaphod.mps.ohio-state.edu!maverick.ksu.ksu.edu!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: <19086@cbmvax.commodore.com> Date: 18 Feb 91 17:55:31 GMT References: Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 40 In article anderson@mrcnext.cso.uiuc.edu writes: >Friend says that there really isn't such a thing as "32-bit" memory. "Friend" needs some memory lessons. >Everyone always says, "you have to get some 32bit mem. if you're going >to buy an '030 board or else it'll crawl... etc." That's true. What "32 bit memory" refers to is the width of the data bus going to the memory system. The 68030 can transact with 8, 16, or 32 bit memory systems. But, all things being equal, it must hit an 8 bit memory system 4 times as much as a 32 bit system to do the same work. So, for the same speed memory system, a 32 bit memory system is roughly twice as fast as a 16 bit memory system. On Amigas, there's more difference than that, however. No one makes fast 68030 bus style 16 bit memory boards. All the 16 bit memory boards are Zorro II bus boards or "sits on the 68000 socket" hacks. In either case, these are 16 bit memory board designed for a 7MHz 68000. The 32 bit memory systems are all faster, in addition to being wider. >but he says that the only difference is the size (ie: 1x8, 256x4...) >and the refresh speed (ie: 80ns, 100ns...). No. Memory _chips_ themselves come in different packages. These packages are generally either 1 or 4 bits wide, though some new DRAMs come as wide as 16 bits. You shouldn't be too concerned with the width of the chip. I can build a 32 bit wide memory system from thirty-two 1-bit-wide DRAMs, eight 4-bit-wide DRAMs, or for that matter, two 16-bit-wide DRAMs. The speed rating, 80ns, 100ns, etc. is the access time, not the refresh time. Access time is a general indicator of how fast that part can be run. The memory board design, not the memory chip itself, determines how fast the memory actually is run. >-Beej -- 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