rowen@mips.com (Chris Rowen) (05/04/91)
> From: appel@Princeton.EDU (Andrew Appel) > Subject: Cache query > > Is the data cache on a Magnum-3000 write-through or write-back? And why > is it so small? The cache is write-through, but with 8 deep write buffer and good DRAM page-mode smarts so that it writes at 1 word/2 cycles (67MB/s) much of the time. Write-buffer stalls are rare (order of magnitude: 1% effect) in most application domains. It is small because 1) a comparatively fast memory system, and 2) decreasing marginal return on cache size. 64KB + 64KB caches instead of 32KB + 32KB caches would yield 5-8% in SPECmarks. This would be roughly a wash in price-performance of the machine. In addition, there are now some excellent integrated cache RAMs for the R3000 at this density which save power, board space and nanoseconds. Chris Rowen - I speak for myself, etc. - rowen@mips.com 928 Arques Ave. Sunnyvale CA 94088