Subject: Re: Cyberstorm (and Amiga cache)
To: None <amiga@NetBSD.ORG>
From: Michael van Elst <firstname.lastname@example.org>
Date: 03/26/1996 00:46:45
email@example.com (Jeffrey William Davis) writes:
>at a finite speed! Clocked at 40MHz, the DRAM subsystem is able to process
>all accesses immediately without any kind of delay (zero wait state).
At 40MHz the CPU can request a longword in 25ns, this requires at least
20ns DRAM. Do you still believe that the Warpengine has zero wait states ?
The fastest reasonable burst cycle is probably a 2-1-1-1 burst. At 40MHz
this yields a possible memory bandwidth of 128MByte/s but the WE memory
system just delivers about 50MByte/s.
>The reason L2 cache is so prevalent in the PC realm (and others) is due
>to the clock doubling, high CPU clock rates, and generally exceeding the
>DRAM technology of today. For example, a 166MHz bus speed on a system
>with 3 clocks/access would require 18ns minimum speed RAM to run at full
No CPU in a PC uses a 166MHz bus. The fastest Pentiums use 66MHz
on the bus and often have waitstates on L2 cache accesses.
Michael van Elst
"A potential Snark may lurk in every tree."