Linux and L2 Cache; Sempron vs. Athlon
by Kristopher Kubicki on August 18, 2004 2:29 AM EST- Posted in
- Linux
Conclusions
The first conclusion we came to without even really running any benchmarks. Primarily, the lack of 64-bit addressing on the Sempron 3100+ probably makes a bit of sense; the A64 2800+ and the Sempron 3100+ are both budget oriented processors - it is very unlikely anyone will utilize more than 4GB of memory on either processor. The real payoff of the Athlon 64 processors (the onboard memory controller) is found on both the Sempron and Athlon 64.
We also noted in our analysis that the Sempron 3100+ scored very similar performance marks to the Athlon 64 2800+; and it should. Both processors utilize 1.8GHz clock speeds and 130nm production, but the Sempron 3100+ only runs on half the L2 cache of the 2800+. Again, the only major functional differences we noticed between the two processors was the lack of 64-bit operation (with a few exceptions). That being said, at least on Linux, we cannot vouche for AMD's PR rating since the Athlon 64 3000+ lead the Sempron 3100+ in every single benchmark. AMD states the PR rating only compares the Sempron to the Celeron product line, but since Intel dropped the GHz rating on the Celeron chips months ago, that seems like a moot point.
On a cost analysis, the Sempron 3100+ packs a lot of punch for $130. We lose 64-bit addressing and the additional cache for $20 when compared to an Athlon 64 2800+, but as we saw in our benchmarks the cache only provided significant advantages on database and encoding applications - not something most people generally use a budget CPU for anyway. If you're looking to limit yourself to 32-bit computing on the Linux desktop, the Sempron 3100+ cannot keep up with an Athlon 64 3000+ or even a 2800+. However, the 10% cost savings between the 2800+ and the 3100+ is much better than the 2 to 5% decrease in performance we saw between the two processors.
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KristopherKubicki - Saturday, August 21, 2004 - link
Aces options actually degrade performance on our test machine.Kristopher
KristopherKubicki - Saturday, August 21, 2004 - link
I am not making these up... really.Xeon 3.6GHz EM64T, 1GB DDR2-400, TSCP 1.8.1
=================================================================
linux:~/work/tscp181 # /opt/gcc-mainline/bin/gcc -v
Reading specs from /opt/gcc-mainline/lib64/gcc/x86_64-suse-linux/3.4.1/specs
Configured with: ../configure --enable-threads=posix --prefix=/opt/gcc-mainline --with-local-prefix=/usr/local --infodir=/opt/gcc-mainline/share/info --mandir=/opt/gcc-mainline/share/man --libdir=/opt/gcc-mainline/lib64 --libexecdir=/opt/gcc-mainline/lib64 --enable-languages=c,c++,f77,objc,java,ada --enable-checking --enable-libgcj --with-gxx-include-dir=/opt/gcc-mainline/include/g++ --with-slibdir=/lib64 --with-system-zlib --enable-shared --enable-__cxa_atexit x86_64-suse-linux
Thread model: posix
gcc version 3.4.1 20040508 (prerelease) (SuSE Linux)
=================================================================
-O3 -funroll-loops -frerun-cse-after-loop -march=nocona
Nodes per second: 388145 (Score: 1.596)
-O2 -funroll-loops -frerun-cse-after-loop -march=nocona
Nodes per second: 365722 (Score: 1.504)
-O3 -funroll-loops -frerun-cse-after-loop
Nodes per second: 378021 (Score: 1.555)
-O2 -funroll-loops -frerun-cse-after-loop
Nodes per second: 365722 (Score: 1.504)
-O3 -march=nocona -funroll-loops -fomit-frame-pointer -ffast-math -fprofile-arcs
Nodes per second: 311526 (Score: 1.281)
-O2 -march=nocona -funroll-loops -fomit-frame-pointer -ffast-math -fprofile-arcs
Nodes per second: 299173 (Score: 1.230)
-O2 -funroll-loops -fomit-frame-pointer -ffast-math -fprofile-arcs
Nodes per second: 279724 (Score: 1.150)
-O3 -funroll-loops -fomit-frame-pointer -ffast-math -fprofile-arcs
Nodes per second: 299173 (Score: 1.230)
Matthew Daws - Saturday, August 21, 2004 - link
Not true. These options are on at least GCC 3.2.2, and on the P4 system I have access to (it's a university computer) I get 422K nodes/sec using the above compiler settings from Ace's.--Matt
KristopherKubicki - Saturday, August 21, 2004 - link
Matthew Daws: Again, he is using GCC 3.4.1 which has huge optimizations and is something we havent moved over to yet.Kristopher
ThePlagiarmaster - Saturday, August 21, 2004 - link
Oops, forgot, MS says 1st half 2005 now for Win64. So we can expect it in June...ROFL. Still the Semprons will be eaten for lunch then by next xmas by 64bit chips that are only $20 more right now. Then again, AMD could just solve the problem by turning on 64bit for Semprons :)Plag
Matthew Daws - Saturday, August 21, 2004 - link
Kris,Sorry to keep harping on here. But if you look over at Ace's:
http://www.aceshardware.com/forum?read=115094123
You'll find the compiler options you need to get much better results (I'm getting 291K now, on a 2GHz celeron). The general opinion is that TSCP favours the P4 without some careful compiler work. The Athlon numbers, with stock compiler options, are probably OK. But the P4 numbers in the older article seem very low...
--Matt
ThePlagiarmaster - Saturday, August 21, 2004 - link
I'm having a hard time with any recommendation of the sempron over 64bit cpus that are only 10% more (we're talking like $20 here). Nobody will use more than 4gb with these. Thats a given. However, the 64bitness can't be overlooked. Look at the examples AMD has already showed (recently for example). That panorama filter they showed with 57% improvement in speed, and the other thing in the same news post showing 47% improvement. AFAIK neither of these were using more than 4GB. This is with a BETA Win64!http://www.amd.com/us-en/Corporate/VirtualPressRoo...
These are only two examples of TONS that will be on the way shortly (immediately following the OS from MS that is). Intel is now backing this stuff too. Expect more 64bit ports, especially with MS finally getting off the collective ARSES and saying windows64 will be done this year (nah, I say jan/feb...but the point's still valid). This stuff is coming (encryption shows HUGE benefits, and zipping too with nowhere near 4GB), why cut yourself from the game for $20? If $20 is going to break your bank, you have no business buying a PC. Spend it on your kids diapers or shoes instead...LOL
Plag
Matthew Daws - Saturday, August 21, 2004 - link
Kris,I found the following in the source file main.c for TSCP 1.8.1:
/* Score: 1.000 = my Athlon XP 2000+ */
Checking, this means that the author gets circa 243K nodes/sec with his Athlon XP 2000+. I think, in light of this, that my numbers seem correct and yours seem way of base.
Cheers, --Matt
balzi - Saturday, August 21, 2004 - link
Helloooo.. !!!! am I using a mute account??is there any answer to the muddle of benchmark graphs.. please humour me by actually saying something.. Even 'I couldn't be stuffed fixing them' would be good.
thanks
PrinceGaz - Friday, August 20, 2004 - link
40-bit physical address space is 1TB, the 48-bit virtual address space allows for a range of up to 256TB. I think that should be sufficient for the lifetime of the Opteron / Athlon 64.