Clocking for maxium memory speed

[Netopia]

Greetings all!

I'm going to start with a lot of explanation and then a basic question at the end.

I have an application that is incredibly disk intensive. It looks up combinations of items from a fairly complex database. Disk based queries were just too slow, so I decided to move the database (it's static... for lookups only) to a RAM drive.

VERY dramatic difference. Somewhere around 40 times faster.

So... the machine I use has a Q6600 on a P35-DS3L mobo with 8GB DDR2 6400 RAM with 7Pro for the OS. Previously, I'd not really overclocked this particular machine much. I had it at around 2.8GHz, but hadn't really looked at the overclocking in any detail. I upped it to 3.2GHz and everything was nice and stable.

SO... doing some investigating, I realized that I was running the memory at half the speed, or at least asynchronously. I changed that so that it was running synchronously and with that alone got about a 14-15% speed increase.

The program, unfortunately, is single threaded, so it only uses one core, but it doesn't max that one core out, so it still isn't CPU bound, it appears to still be bottlenecked soley by data access speed.

My question is this. Could I switch to a set of DDR2 1066 modules and run the memory in a mode that ups the memory to that speed while not stressing or overclocking the rest of the machine farther than it already is? Heck... I'd even be willing to reduce the OC on the CPU if I could get even faster I/O with the memory.

Right now, I'm cranking work out at about 45 times faster than a stock machine in the normal configuration (spinning disks) does, but if I could crank the memory from 800 to 1066 and get another 33%, that would have me around 60 times the speed. What took an hour done in a minute!

So... is this doable? Can I simply plug in DDR2 1066 sticks, change the ratios and get the memory to run at those speeds? Would I be able to do that and keep the memory synchronous with the CPU?

Thanks in advance for any and all replies,

Joe

 

[fffblackmage]

Yes, as long as the mobo supports DDR2-1066, it shouldn't be a problem. However, I think you'd be then limited by the FSB. If the FSB isn't as fast as the memory, you'd probably have a bottleneck.

I'm not certain this is how it works, but I always though that with dual channel memory, 2x DDR2-800 is like having a single uber stick of DDR2 running at 1600MHz. At that speed, you need at least a 1600MHz FSB to make full use of that bandwidth though.

Assuming that's kinda how it works, you'd probably see a lot of trouble trying to bump up the FSB that high with a quad core processor.

Hopefully, someone will provide more insight on this.

 

[BenchZowner]

High memory frequencies with low FSBs are often bottlenecked by the FSB.
You should max out your FSB and clock the mems as high as possible at that FSB and use the lower multipliers of your processor to keep the CPU's overclock close to what it is now.

400MHz FSB should be doable on your config ( with the appropriate NorthBridge voltage & cooling )

 

[DrMrLordX]

If he's willing to switch mobos, there are cheap G31 boards out there that will hit 480 mhz FSB.

Zap reviewed one such board here:

http://forums.anandtech.com/showthread.php?t=269319

 

[Netopia]

I'm already at 400MHz FSB (8 * 400 for 3.2GHz).... stock cooling. I thought that's what the Q6600 and PC 6400 were supposed to be set at for optimum.

Hmmm.... I think I'm ok with the FSB going no further, just the internal speed of the ram disk needs to be increased. There are a ton of lookups within the database before the data comes back, so perhaps the 400MHz FSB is fine. As I said before, moving from a 200MHz FSB to a 400MHz FSB did give me a 14% improvement, so it made some difference, though the memory was running at 800MHz in both situations.

Joe

 

[Netopia]

If he's willing to switch mobos, there are cheap G31 boards out there that will hit 480 mhz FSB.

Zap reviewed one such board here:

http://forums.anandtech.com/showthread.php?t=269319

It's a work machine, so I don't want to take it out of production, just boost its performance as much as possible. In a weird turn of events, Zap and I are on three forums together and I never thought about just asking him his thoughts! DOH!

Joe

 

[DrMrLordX]

Well in that case, just ask him . . . he'll set you on the proper course. Better than I could, anyway, since my s775 knowledge is a tad limited.

edit: you might also want to look into tightening the timings on your RAM instead of overclocking it to see how that affects your RAMdisk performance. Not sure what the motherboard's BIOS will allow, of course, but it's worth looking into it.

 

[Zap]

Joe, what's the budget and how long downtime can it suffer?

You're on the right track for optimizing the hardware you have. If you can only do minimal downtime, then perhaps consider swapping in a high end Core 2 Duo/Xeon. You said the software is single threaded. Core 2 Duos seem to be able to hit higher FSB than Core 2 Quad, especially old Kentsfield cores. Just make sure the mobo chipset has good cooling. Pop in a Xeon E3110 or Core 2 Duo E8200/E8400 with some DDR2-1066 and crank those bus speeds.

If you can suffer a bit more downtime and have a bit more budget, and since you have reason to believe that more memory/bus bandwidth = greater performance for the RAM drive, go with a socket 1366 setup. With triple channel DDR3-1600, you can TRIPLE dual channel DDR2-800 bandwidth.

 

[Netopia]

Downtime available is near zero, as is budget.

Is there a way I could test the memory at 1066 (not current modules) and keep the CPU FSB at 400 or whatever is best?

I tried bumping the FSB just a bit, up to 410, and the machine crashed within a couple of minutes. I don't want to stress things too much, as this is a company machine and they aren't willing to pay for extra cooling et al.

Joe

 

[Zap]

You should have higher memory multipliers, so yes you can run RAM above bus speeds. As I mentioned, Kentsfield cores didn't like high FSB too much, so no suprise that it crashed.

Why not just leave "well enough" alone? sounds as if you've already significantly increased performance just by going to the RAM drive. If anyone complains about performance to you, just throw your hands up in the air, sigh really loudly and complain about not having the IT budget for upgrading.

 

[fffblackmage]

I think I've tried running ram above FSB speeds just to see if that did anything for performance. Don't think it did.

 

[Netopia]

Why not just leave "well enough" alone? sounds as if you've already significantly increased performance just by going to the RAM drive. If anyone complains about performance to you, just throw your hands up in the air, sigh really loudly and complain about not having the IT budget for upgrading.

Great Point! It's the inner tweaker inside of me that wants every last minute amount of whatever I'm trying to get. But your logic is sound!

I'm done!

Joe