Date: Tue, 22 Jul 1997 23:02:39 +0200 From: Stefan Esser <se@FreeBSD.ORG> To: freebsd-hardware@FreeBSD.ORG Cc: owner-crp@tssc.co.nz Subject: Re: Best Pentium / PPro Message-ID: <19970722230239.56696@mi.uni-koeln.de> In-Reply-To: <199707211016.DAA20983@silvia.HIP.Berkeley.EDU>; from Satoshi Asami on Mon, Jul 21, 1997 at 03:16:22AM -0700 References: <3.0.32.19970721101544.006c0e1c@mailhost> <199707211016.DAA20983@silvia.HIP.Berkeley.EDU>
next in thread | previous in thread | raw e-mail | index | archive | help
* Any comments with DIMM (10ns) vs EDO SIMM (60ns) memory, it seems like the * 10ns DIMM is not worth the extra money due to the PCI bus speed ?? Be careful with those numbers! The SDRAM modules are not *that* much faster than EDO, in reality. The reason is, that while the 60ns specified for "normal" DRAMs is the row access time (time from the row address being stable and clocked into the RAM chip) until data is available, while the 10ns in case of the SDRAM is the data rate at which you can read further values after waiting much longer (say 60ns :) for the first data to arrive ... In fact, SDRAM seems to allow 5-1-1-1 clock reads at 66MHz, while EDO-RAM needs 4-2-2-2. This means that on average 5% of the memory reads that are not covered by the secondary cache are going to take 8 instead of 10 clocks with SDRAM. You will see a difference, if your application accesses large blocks of memory (much more than fits into the cache). In typical system benchmarks (CPU bound) SDRAM seems to give at most a 1% to 2% improvement over EDO. Regards, STefan
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19970722230239.56696>