Date: Sat, 14 Aug 1999 19:50:17 +0200 (CEST) From: Wilko Bulte <wilko@yedi.iaf.nl> To: rgrimes@gndrsh.aac.dev.com (Rodney W. Grimes) Cc: mike@smith.net.au, freebsd-stable@FreeBSD.ORG Subject: Re: On freezes in 3.2-Stable (fwd) Message-ID: <199908141750.TAA58960@yedi.iaf.nl> In-Reply-To: <199908141707.KAA05443@gndrsh.aac.dev.com> from "Rodney W. Grimes" at "Aug 14, 1999 10: 7:45 am"
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As Rodney W. Grimes wrote ... > > As Rodney W. Grimes wrote ... > > > > > > Er. The Intel AD450NX has 32 DIMM sockets. Unless someone starts > > > > making 2-chip DIMMs, I don't see how you would run 8GB in this box (and ... > > > supper honking driver that can drive 288 chips in the memory controller, > > > but then all the RAM chips would have to have larger data drivers to > > > handle that side of the bus. > > > > You could use buffered DIMMs I guess. Not really PC standard stuff though. > > If the memory controller was designed to deal with them, or > you use faster DRAM's themselves to compensate for the additional > delay that buffered DIMMS add. 6nS DRAM'S price difference would > probably be more than going from a clone MB to one like the AD450NX > that is designed for large memory modules. You obviously need to adapt the rest of your memory logic. The buffered memory module approach is what is often used in the higher-end server machines. Like what I see in the big Alpha boxes etc. > Also buffered DIMMS usually take care of the address line loading issue, > you may still have a problem with the databus drivers in the DRAM chips > being able to drive data back to the CPU. Buffering both the data and > address lines would push you close to needing 5nS chips. (The address > lines see one package pin of loading for each chip in the whole memory > array, datalines see one, two or four package pin of loading for each > DIMM in the array, dependent on single or double row, normal or low > density dimms.) Memory design is an art form. I know. I've seen memory boards being designed while I was in hardware design, but never got around to do it myself though. Wilko -- | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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