2x1GB vs 4x1GB ---> What good does 4-way interleaving do for AM2

[bachus_anonym]

As some of you sure know, filling all 4 DIMM slots with 512MB or 1GB modules triggers 4-way interleaving - as opposed to 2-way interleaving with only 2 DIMM slots populated with dual rank modules. This scenario potentially opens up a window of opportunity for some gain in memory performance.

On Socket939, running 4 DIMMs mostly required Command Rate 2T in order to not only achieve some decent OCs but even to fire your system up. But that on the other hand had some impact on performance drop, which destroyed any gains 4-way interleaving gave us. It was very noticeable in benchmarks but less in games.

Now, since SocketAM2 requires Command Rate 2T anyway, there is a chance that finally on this platform 4-way interleaving can give somewhat of a boost. Today I've been messing around with 4x1GB memory config on my SocketAM2 platform, running mostly SuperPi 32M, 3DMark2001 and 3DMark03. Those are the results I got so far and SuperPi 32M comparisions are particularly interesting


2x1GB @ DDR2-966 8-4-4-4.0-2T --> SPi32M 25:01 ------ 4x1GB @ DDR2-966 8-4-4-4.0-2T --> SPi32M 24:41


2x1GB @ DDR2-966 8-4-4-4.0-2T --> 3DM01 & 03 ------- 4x1GB @ DDR2-966 8-4-4-4.0-2T --> 3DM01 & 03


At DDR2-966 I got a nice 19s boost in SuperPi 32M Also 3DMark03 got 50 points extra, not that much though. Then there is 3DMark2001 that needs to be looked at a bit differently, due to a variation in CarLow. I might actually rerun this one...


2x1GB @ DDR2-1080 8-4-4-4.0-2T --> SPi32M 26:44 ---- 4x1GB @ DDR2-1080 8-4-4-4.0-2T --> SPi32M 26:11


Whoa, 33s shaved in SPi32M I did that comparo 3 times and got same result +/- 2s. This is something very interesting to see as it appears that the higher memory clock the bigger gain from 4-way interleaving. This is only my speculation, though.

I did not have enough time to run 3D at DDR2-1080 yet but I expect some good stuff as well. I will also run WinRAR benchmark, couple games and 2 more other benches. But it looks like getting 4 modules is definetely a way to go for SPi32M benchers on SocketAM2.

[eva2000]

interesting for 32M too on AM2

[bachus_anonym]

interesting for 32M too on AM2

Your case (2x1GB vs 2x512MB) is different as in both scenarios you're still on 2-way interleaving, even on Intel as far as I know. So, I would not get overly excited about those gains you think of, that 2x1GB would give you compared to 2x512MB. But you will have to try it yourself to see and believe On AMD 2x1GB does not speed things up as far as 32M go. I don't think Intel platform is much different.

[^don.k's^]

Nice boost, does OC decrease using 4 sticks ? I mean, if you get 1200mhz with 2 sticks and 1100mhz with 4 sticks...

Regards!

[bachus_anonym]

Nice boost, does OC decrease using 4 sticks ? I mean, if you get 1200mhz with 2 sticks and 1100mhz with 4 sticks...
Regards!

Hey man! Well, hard to say... Both 2GB kits I used hit the 32M and 3D stability ceiling at DDR2-1100 and DDR2-1140 @ 2.5v respecively. Then as you can see, with 4 sticks I max out at DDR2-1080 @ 2.5v. So, there is a loss but very little from what it appears. I'd bet more volts will fix that but I did not get around to vdimm mod yet

[dogsx2]

Great work b_a. Keep testing. This is the kind of info we need.

When I asked this question in this thread: http://www.xtremesystems.org/forums/...d.php?t=105348, no one thought it would do any good. You have shown that it does make a difference. Is it worth the price of another 2 GB set of ram? That's not what this forum is about, it's about adding hardware that will give faster benches and fps.

Thanks

[JNav89GT]

bah
you beat me to it!
I had the same theories on this and just haven't had the time or ram inhouse to test.
Good job bacchus. I know for AM2 this is an area where we will look to performing better. My thoughts are with XP-64/Vista that 4gb will probably be like 1gb was for XP. So it will be an area where users that expect power and performance migrate towards . Compariing to 939 I think that's really where the gains are, and why AMD is coming into DDR2 at about the right time I think.

[^don.k's^]

Do they get hot as hell ? Ive tried 4x8000ul sticks, cpu went up to 75º, and sticks were burning, REALLY, i'd have burned myself if i were touched'em for longer than 1 second...

[nn_step]

not to sound like an ass or anything but for the most part Can't you run T1 on your DDR2 Memory? Because I know I can

[Tonucci]

Good job man, now i wanna see this kind of test with Conroe aswell .

ps: any pics nn step ?

[RyderOCZ]

not to sound like an ass or anything but for the most part Can't you run T1 on your DDR2 Memory? Because I know I can

on AM2 you can only run it to about DDR800ish...on Intel....its all 2T from the get go.

Nice work Bachus...very thorough...when I get more time I will read the whole thing...hehe

[GSKILL TECH]

very nice job Bachus
try sandra you will see 4 dimm bandwidth is about 200 more than 2 dimm