Subject: Re: VIA VP2 chipset
To: None <current-users@NetBSD.ORG, port-i386@NetBSD.ORG>
From: David Jones <>
List: current-users
Date: 02/01/1998 20:59:28
Greg A. Woods wrote:
| If I can find ECC SDRAM DIMMs (though I have not yet even found a
| manufacturer that makes them yet), I'll use them, but at the moment it
| seems 64MB (x72bit) EDO DIMMs are the best you can find, at least hear
| on the open market in Toronto.  If anyone has any comments on the
| improved memory bandwidth of SDRAM over EDO with the VP3 I'd be most
| interested....

Why do you need ECC?

SDRAM DIMMs are fairly common, at least in Ottawa.

In general, SDRAM bandwidth is limited to 66 MHz, whereas EDO maxes out
at 40-50 MHz.  However, the row access time (tRAC+CAS latency 3) for SDRAM
is longer, so random accesses don't perform as well.  SDRAM is best for
cache controllers that can look ahead and schedule their accesses.

The Intel-100 spec is coming out.  This spec clarifies CLK-to-Q delays
for SDRAMS, and will result in 100 MHz SDRAMs (current 100 MHz SDRAMs
don't have a good enough CLK-to-Q delay, so they are run at only 66 MHz.)
So you might want to wait a year.

Then again, wait two years.  At that point SLDRAM will be out, with
600 MHz transfers from CPU to memory.