daveh@cbmvax.commodore.com (Dave Haynie) (05/30/91)
In article <595.2842FE8C@busker.fidonet.org> DAN.BENDIKSEN@f601.n105.z1.FIDONET.ORG (DAN BENDIKSEN) writes: >I was wondering if there is any advantage to using static column rams that >are faster than 80ns, and if so, what is the best speed, and the fastest >speed that will still give you improved performance. No, faster memories won't do you any good. That's not how memory works. The speed of the memory cycle is determined by the memory controller, RAMSEY in this case. The speed of the memory device itself will determine whether the memory system actually acts like a memory system all the time, but it has no impact on how fast that memory system goes. RAMSEY drives a 240ns cycle/120ns burst at 16MHz, 200ns cycle/80ns burst at 25MHz. If the memory chip is fast enough, the system works, if not, it fails. -- 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.
DAN.BENDIKSEN@f601.n105.z1.FIDONET.ORG (DAN BENDIKSEN) (06/01/91)
>The speed of the memory cycle is determined by the memory controller, >RAMSEY in this case. The speed of the memory device itself will determine >whether the memory system actually acts like a memory system all the time, >but it has no impact on how fast that memory system goes. RAMSEY drives a >240ns cycle/120ns burst at 16MHz, 200ns cycle/80ns burst at 25MHz. If the >memory chip is fast enough, the system works, if not, it fails. >-- >Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" Ok then, is it possible to increase the speed of the A3000 beyond 25 mhz? Or, would it be possible to increase the speed of RAM accesses. I am most interested in the possibilities of running an 040 at >40 mhz. One other thing... The chip RAM speed. Does the CPU still access it at 7.14 mhz, or has chip RAM also been increased to 25 mhz for CPU accesses? Dan Bendiksen. -- DAN BENDIKSEN - via FidoNet node 1:105/14 UUCP: ...!{uunet, reed}!glacier!busker!601!DAN.BENDIKSEN INTERNET: DAN.BENDIKSEN@f601.n105.z1.FIDONET.ORG
daveh@cbmvax.commodore.com (Dave Haynie) (06/03/91)
In article <618.28484461@busker.fidonet.org> DAN.BENDIKSEN@f601.n105.z1.FIDONET.ORG (DAN BENDIKSEN) writes: > >The speed of the memory cycle is determined by the memory controller, > >RAMSEY in this case. >Ok then, is it possible to increase the speed of the A3000 beyond 25 mhz? >Or, would it be possible to increase the speed of RAM accesses. I am most >interested in the possibilities of running an 040 at >40 mhz. The A3000's motherboard/system bus will go at either 16MHz or 25MHz, period. Nothing is expected to run at any other clock speed. A coprocessor device that goes faster than the motherboard should have its own private memory and/or cache and sync-up to the motherboard, like an A2000 coprocessor device does. Zorro III bus devices can run about as fast as they like, though when they access the A3000 motherboard, the transaction speed is limited by the A3000 motherboard clock. >One other thing... The chip RAM speed. Does the CPU still access it at 7.14 >mhz, or has chip RAM also been increased to 25 mhz for CPU accesses? No, the CPU access speed is the same, just 32 bits wide rather than 16 bits wide as on the A2000 and A500. It doesn't make sense to refer to Chip RAM access as "7.16MHz" or "25MHz", since they really doesn't say anything about what's happening. The CPU always runs at 25MHz (in a 25MHz system), it just takes waits states when accessing Chip RAM. The Chip bus is synchronous to Agnus. It runs a 560ns cycle, consisting of two 280ns memory accesses, one of which the CPU can use if the blitter, copper, or video fetch don't lock it out. The only way to let the CPU in for more cycles is to double the memory speed during the CPU access window. That would require a 140ns cycle and a faster Agnus. That's not quite attainable yet. When 60ns DRAMs become as cheap as 80ns, that may be something to consider. Software has done more for system performance that this would, anyway, by moving as much as possible into Fast RAM. Fast RAM will always be faster than Chip to the CPU, no matter what you do. As of 2.0, the only things that go in Chip RAM are those that have to go in Chip RAM. -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "This is my mistake. Let me make it good." -R.E.M.