Can a single core AM2 Athlon64 run with DDR2-800?

[TomMe]

Apparantly only dual core AM2 CPUs officially support DDR2-800, but I was wondering if you can run memory at that speed with a single core AM2 Athlon64 3500+, or will you be forced to use DDR2-667?

Thanks.

 

[coolpurplefan]

Uh, as far as I can tell from benchmarks, there is no difference between socket 939 at 400 MHz and socket AM2 at 667 MHz or 800 MHz which leads me to believe the only reason socket AM2 exists is to introduce K8L later on. But, I can`t prove it.

I`ll put it to you this way. Since I`m so scared of dual core issues with X2s, I decided to get a socket 754 3700+ and I have 2GB of OCZ Platinum RAM. I got pretty good prices or both. So...

 

[JPH1121]

I doubt there is any point in running DDR2-800 on a single core CPU. There isn't really a tangible gain with twice the cores which would use twice the peak bandwidth...so relaly, I don't think there's a point to running your memory that fast. Tighten up the timings and you'll get better results.

 

[TomMe]

According to these and other charts, there should be an improvement with DDR2-800 over DDR2-667. Of course, those charts are for dual cores.

I see something similar here. They used an A64 3500+ with DDR2-800 memory, but I'm not sure if the CPU is a final model. Hence my question.

 

[the Chase]

Or buy the DDR2-800 memory and tighten the timings way up. You'll give up some memory speed but not as much as trying to tighten up with DDR2-667. Edit - I see your question. The DDR2-800 should run - but the IMC on the CPU may not handle the top speeds of the memory.

 

[TomMe]

Do you mean buy DDR2-800 memory, run it @ 667 and then tighten the timings? Otherwise I'm not quite sure what you mean.

Are there any DDR2-800 sticks with 5-5-5 timings out there that can run @ 667 with 4-4-4 timings?

 

[TomMe]

bump

 

[the Chase]

Originally posted by: TomMe
Do you mean buy DDR2-800 memory, run it @ 667 and then tighten the timings? Otherwise I'm not quite sure what you mean.

Are there any DDR2-800 sticks with 5-5-5 timings out there that can run @ 667 with 4-4-4 timings?

Actually just read some more threads on single core AM2 chips. One guy was running DDR2 - 800 at well over 1000Mhz so it looks like you can use DDR2-800 no problem. Depending on what divider you use you should be able to run whatever speed the memory and CPU can handle. Memory timings will play into this. You will have to see what is faster for you- say 4-4-4 timings at 800Mhz or 5-5-5 timings at say 1000Mhz or whatever the CPU speed x divider ends up running your memory at. Of course you have to have stability also so that will play into how tight/fast you can run the memory.

Edit- yeah if it was me for AM2 I would try to tighten the timings as much as I could say at 3-4-4-11 and use a divider that would run the memory slow enough to be stable. But you might find that if you loosen timings just a bit you might be able to "move up" 1 divider to run your memory somewhat faster. Not sure if it's worth the cost for DDR2-800 memory though. Overclocked DDR2-667 might perform almost as well for considerable savings.

 

[TomMe]

Originally posted by: the Chase
Actually just read some more threads on single core AM2 chips. One guy was running DDR2 - 800 at well over 1000Mhz so it looks like you can use DDR2-800 no problem.

I've been looking around but I can't find the thread you mention. And the search function only shows me threads from March and older.

Edit- yeah if it was me for AM2 I would try to tighten the timings as much as I could say at 3-4-4-11 and use a divider that would run the memory slow enough to be stable. But you might find that if you loosen timings just a bit you might be able to "move up" 1 divider to run your memory somewhat faster.

Hm, don't those charts I posted already show that DDR2-800 outperforms DDR2-667 at any timings? So why would I slow down the memory and tighten the timings, or am I missing something here?

Not sure if it's worth the cost for DDR2-800 memory though. Overclocked DDR2-667 might perform almost as well for considerable savings.

Prices around here are about the same for 667 4-4-4 and 800 5-5-5, so my choice would be easily made considering 800 is faster anyway.

Thanks for your help so far!

 

[the Chase]

The thread was in a different forum - will try to find and link. The graphs you linked to were pretty close in perf. and if you turn up the res. in the game benchies you will probably see no dif. at all. But yeah, if you can find DDR2 800 memory with decent timings for the same $ as DDR2 667 then the choice is easy. It always seemed in the past the a64 arch. liked tighter timings at the expense of speed...Some of the benches coming out now seem like it's a toss up depending on the application whats best- timings or speed. It all depends on the memory you end up with, what CPU speed your shooting for, with what divider you have to use to hit that CPU speed at certain memory timings. Lots of combinations possible.

 

[the Chase]

Here is a quick comparo of different memory speeds and timings- http://www.techpowerup.com/printreview.php?id=/Mushkin/XP2-5300 - bah- thats on a P4 system....srry.

And the thread on memory it came from- http://forums.anandtech.com/messageview...atid=27&threadid=1869594&enterthread=y

 

[the Chase]

Here's the link. It's actually DDR1000 that he's running on a AM2 3000+ at 1122Mhz!! Apparerntly the memory controllers on AM2 can handle any memory speed that you can through at it. So the only limit really is how high the memory is rated for/can clock to. http://www.xtremesystems.org/forums/showthread.php?t=100814&page=3

Edit- it also shows the various memory timings he was able to achieve at the different memory speeds.

 

[TomMe]

Hm..after looking around a bit on the web, I'm beginning to think that JPH1121's advice is well justified and that there is little point in running @800 over 667 for a single core. The t-break preview shows marginal differences, sometimes even better for 667.

It took me a while but I finally understand what you are saying the Chase. You meant buying DDR2-800, and decreasing speed as I tighten timings. But if with single cores DDR2-800 is on par with DDR2-667, it seems rather useless to do so.

I think I'll be going with a good set of DDR2-667 sticks at a good price! Thanks for all your help!

 

[A554SS1N]

If you want to overclock, it'll be handy having DDR2 800Mhz over 667Mhz so that the RAM divider(?) can be kept the same.

 

[TomMe]

Not sure if I'll be overclocking, maybe just a bit if I have performance problems.

Hm, what do you mean by keeping the RAM divider the same? I'm still learning..

 

[A554SS1N]

Originally posted by: TomMe
Not sure if I'll be overclocking, maybe just a bit if I have performance problems.

Hm, what do you mean by keeping the RAM divider the same? I'm still learning..

Well, I assume it's a divider still with DDR2 - might be a multiplier. Anyway, the way I've read it, with DDR frequencies and for example DDR400MHz memory, runs at 200MHz, and the motherboard bus is 200MHz, so it's said to be '1:1' (I think) in terms of a ratio. Now, the memory frequency is got from the motherboard bus (people call it FSB), and to overclock a CPU, the FSB needs to be increased, which would mean the memory speed would need to increase at the same ratio. Most memory can't increase much, especially if the FSB needs to increase a lot, so a divider is used on the ratio, i.e. for example, 1:2, to halve the memory speed relative to FSB speed. The problem is, it's not always possible to get the RAM running at a good divider that gives either a RAM speed that's not too slow, or one that exceeds the rated frequency of the RAM, so to get better RAM performance, faster RAM can be used that is rated at higher frequencies, so when you overclock, the memory can stay at a better divider, or at 1:1.

I'm not sure I've got it all right, I'm a bit hazy on it myself, but theres a good link here that might explain it: http://en.wikipedia.org/wiki/Athlon_64

Hope that helps!

 

[TomMe]

Sorry for the late reply.. Tried to find the time to read that all, haven't finished it yet but looks very interesting. I ordered some Corsair 512MB DDR2-667 XMS sticks for a good price though. I'd rather wait to buy 2GB DDR2-800 or higher when prices drop and timings are tighter.

Thanks for the info!