Author: Tom Kerrigan
Date: 15:42:47 06/13/00
Go up one level in this thread
On June 13, 2000 at 18:25:31, stuart taylor wrote: >On June 13, 2000 at 17:59:03, Tom Kerrigan wrote: > >>On June 13, 2000 at 17:27:45, Torstein Hall wrote: >> >>>On June 13, 2000 at 17:01:36, Tom Kerrigan wrote: >>> >>>>On June 13, 2000 at 15:55:24, Mogens Larsen wrote: >>>> >>>>>On June 13, 2000 at 15:41:51, Tom Kerrigan wrote: >>>>> >>>>>>No, Thunderbird is a few % faster than an Athlon at same MHz. >>>>>> >>>>>>Duron is exactly the same as Tbird, but with 1/4 the L2 cache (64k). >>>>>> >>>>>>-Tom >>>>> >>>>>I've just purchased an ordinary Athlon. What are the advantages and >>>>>disadvantages with a smaller cache size. BTW, are the L2 cache of the >>>>>Thunderbird and the Athlon fullspeed? >>>>> >>>>>Best wishes... >>>>>Mogens >>>> >>>>The Tbird and Duron both have on-die "full speed" L2 caches, but they are not >>>>that much faster than the old off-die caches. Most benchmark scores improve by a >>>>few percent, but nothing like when Intel moved the PIII cache on-die. >>>> >>>>The main benefit of the on-die cache is that it makes the processors much >>>>cheaper to manufacture. Another, less significant benefit is that the cache >>>>performance can now scale with the processor performance. >>>> >>>>-Tom >>> >>>Why was it so much more important for the PIII to get the cach on-die? >> >>Primarily because the PIII has a small L1 cache--16k or 32k, I can't remember >>which. But it relies heavily on the L2 cache, as opposed to the Athlon, which >>has a 128k L1 cache. >> >>Another thing is that Intel redesigned the PIII's L2 cache when they put it >>on-die, so the bandwidth is higher and the latencies are lower. AMD simply took >>their cache chips and splatted them on the processor die, so there's no reason >>for the on-die cache to be much better than the off-die cache. >> >>-Tom > >Therefore, is a normal Athlon with 512k L2 off-die cache still better than >thunderbirds 256 on-die L2 cache? (if I got the numbers right). And overall >is it superior to intel at the momment? >S.Taylor No. The cache is not blazingly fast, but it's fast enough to make up for being smaller. Overall, the Tbird (new Athlon) is slightly faster than the old Athlon. Also, the on-die cache is exclusive, meaning that data will either be in L1 or L2 cache but not both at the same time. AMD claims that this makes the on-die cache the equivalent of 384k of old off-die cache, although this claim is somewhat questionable... L2 cache size can have a big impact on the speed of your programs, but I think that for most programs, 128k is enough. Notice that the Celeron doesn't seem to be hurt much by its small L2 cache... -Tom
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