Athlon 64 Question

[jaylow]

I have begun to research the Athlon 64's and... I have a question that I'd like answered... with some more research I could probably find it... but if someone could just lemme know... that'd be terrific... mmmkay!

OK... so we got the Athlon 64 FX's and the newer Athlon 64 3700+ and 3800+... my question is... what is the real difference between let's say... the 3700+ and the FX 53 or whatever it is... they both run at 2.4 GHz and both have 1 MB L2 Cache... is the core the difference? Please lemme know!

 

[TheRod]

Athlon 64 3700+ = Socket754, SINGLE-CHANNEL memory controller, 1024K of cache
Athlon 64 3800+ = Socket939, DUAL-CHANNEL memory controller, 512K of cache
Athlon FX-53 = Socket939, DUAL-CHANNEL memory controller, 1024K of cache

Et voilà!

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[jaylow]

So you have to pay a couple hundred extra dollars to get dual channel eh... me and my roomie have the exact same configurations on our systems... yet he has a GB of dual channel where I have only 512 MB of single... the only game I see a difference in is Everquest... We play a lot of other games and the performance is the same. I guess it's nice to have dual! (I know dual is good... I just wish it wasn't so expensive!)

 

[TheRod]

I guess it's nice to have dual! (I know dual is good... I just wish it wasn't so expensive!)

DUAL-CHANNEL is not the best thing on earth. In fact, DUAL-CHANNEL was introduced fo Intel P4, because this architecture is dependant of the memory bandwidth. If you chack Athlon XP benchmarks with single or dual channel setup will see that there is not much difference in performance. The AMD architecture is less dependant on the memory bandwidth.

The new Athlon 64 CPU's come in 2 flavor : single-channel (Socket754) and dual-channel (Socket939), of course, dual-channel boost a bit the performance, but check the A64 rating, 3700+ vs 3800+, this mean only a few percentage increase in performance. So, if you can't live with a single-channel A64 system, is that you don't understand how this influence performance.

The AMD PR for A64 is clear, you get +100 (or +3%) with DUAL-CHANNEL compared to single channel. The only reason you pay a premium for dual-channel it's because AMD have yet to release slower AMD64 for the S939 platform.

But some readmap shows that by the end of 2004 (or early 2005), AMD will have Athlon 64 from 3000+ to 4000+ for the socket939 platform.

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[johy99]

Great post. Loved reading it.

Also, just wanted to add this. AMD FX-51, which is socket 940, but requires registered memory (expensive), dual channel support.

AMD FX-53 is available in both socket 940 and socket 939 (both at 2.4 Ghz frequency). The socket 940 requires registered memory (like the FX-51), dual channel for both.

Thanks

 

[TheRod]

Thaks!

I didn't mention Socket940, because I consider this platform only interesting for workstations and servers. AMD porbably wanted to please Socket940 owner with the FX-53 for this platform, but I doubt they will release FX-55 on socket 940.

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[P4Man]

>The AMD PR for A64 is clear, you get +100 (or +3%) with
>DUAL-CHANNEL compared to single channel.

Ahem, not quite. Remember S939 chips only have 512 Kb versus 1024 Kb for identical clocked and (almost identically) PR-rated S754 chips. Now 512 Kb doesn't make a world of difference either, but your 3% gain for dual channel is a bit off.. Dual channel offsets 512 Kb less cache *and* boosts PR ratings with some meaningless 3%... considering newcasttle versus clawhammer there is difference of 200 PR points for 512 versus 1024 Kb cache (same clock, both single channel), it seems dual channel does a bit more: 200 extra PR point + 3 %

= The views stated herein are my personal views, and not necessarily the views of my wife. =

 

[TheRod]

Oups! You are right I forgot that...

But, if we check performance numbers of the 3500+ vs the 3200+ with only 512K of cache even with a PR difference of 300, the performance difference between both CPU is about 5%. In fact, in non-memory bandwidth sensitive benchmarks the 3200+ is not slower than the 3500+ (see MAYA, 3Dstudio). the 3500+ DUAL-CHANNEL shine in games.

So, it's hard to say that the DUAL-CHANNEL gives a specific boost... So, I should correct my statement and say that the DUAL-CHANNEL gives between 1 and 5 percent increase.

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