jbell@grofe.DEC (Jeff Bell) (12/20/85)
Most people agree that cacheing is a good way to improve the performance of scalar machines. Does anyone have information on the use of caches in vector machines? Has anyone ever built a cached vector machine? How much bigger does it have to be to get a reasonable hit rate. Jeff Bell ARPA: jbell%tallis.DEC@decwrl.ARPA UUCP: ....!decwrl!tallis!jbell [replace this line with your favorite disclaimer]
brooks@lll-crg.ARpA (Eugene D. Brooks III) (12/24/85)
As for the Cray series, the clock speed is just too fast to build a cache. The vector registers are used for explicit caching. Take note that in the Convex C1 where the clock speed is slow enough to allow a conventional cache, the vector functional units bybass the cache. This done to keep vector operations from flushing the scalars out of the cache.
rchrd@well.UUCP (Richard Friedman) (12/24/85)
In article <125@decwrl.DEC.COM>, jbell@grofe.DEC (Jeff Bell) writes: > Most people agree that cacheing is a good way to improve the performance > of scalar machines. Does anyone have information on the use of caches > in vector machines? Has anyone ever built a cached vector machine? > How much bigger does it have to be to get a reasonable hit rate. > > Jeff Bell > ARPA: jbell%tallis.DEC@decwrl.ARPA > UUCP: ....!decwrl!tallis!jbell > The Alliant FX/8 and the IBM 3090 (370-XA) are chached vector machines. (Virtual memory). As a result, both Alliant and IBM are looking at new algorithms that take the cache in mind. With these machines it is possible to be computing thru the cache faster than the cache can be filled from real memory. The result is that after some problem size the performance is degraded. New algorithms (FFT, LINPACK etc) must be devised that "strip mine" the problem so as much as possible can fit into the cache. ...Richard Friedman [rchrd] Pacific-Sierra Research 2855 Telegraph #415, Berkeley CA 94705 (415) 540 5216 USENET: {lll-crg,ptsfa,hplabs}!well!rchrd -- ...Richard Friedman [rchrd] Pacific-Sierra Research 2855 Telegraph #415, Berkeley CA 94705 (415) 540 5216 USENET: {lll-crg,ptsfa,hplabs}!well!rchrd