Autoset RAM frequency

[AmberClad]

I asked this in Motherboards and over at HardForum a while ago, but didn't get a satisfactory answer in either case.

The (possible) issue: I noticed recently that my board is running my DDR2-800 at 800 MHz...even when there's no OC on the CPU. My understand of RAM and FSB is a little murky, so correct me if I'm wrong, but I thought that the CPU is unable to use the additional bandwidth if the RAM frequency is higher than the FSB. So DDR2-800 is supposed to run at DDR2-533 speeds with an non-OCed CPU. Something about synchronous vs asynchronous operation.

Is there any benefit to the board trying to run it at 800 MHz? Any potential issues?

The board also seems to be overvolting the RAM slightly (1.84V) under Auto settings. Should any of these things be cause for concern?

 

[JustaGeek]

FSB and the Memory Bus use the same clock.

In order to make both bus speeds more "independent", there is something called the "Memory Divider", or DRAM/FSB Ratio.

In my case, I set my FSB frequency at 325MHz (actually I set it in BIOS at 1300MHz, since that is the "quad pumped" speed for the Intel FSB, but divided by 4 it gives you the "base" FSB speed). That's the hard part, since all that works with the Multipliers and Ratios.

Anyway, with the 325MHz "base" FSB speed, and 16/13 DRAM/FSB ratio, the Memory Bus speed will reach 400MHz, and then it will be multiplied by 2 for the 800MHz DDR (Double Data Rate) memory speed.

In your case, if you set the memory speed on Auto, and the memory is recognized by the Motherboard as DDR2 800 (through the memory SPD chip), the memory divider will be set Automatically by the Motherboard.

If your FSB is 266MHz, and the RAM speed is 800MHz, the board will automatically set the Memory Bus divider at 3/2.

266MHz FSB x 3/2 Divider = 400MHz Memory Bus x 2 DDR = 800MHz Memory speed.

The "Memory" tab in CPU-Z will show you the FSB: DRAM ratio.

Hope this helps.

 

[AmberClad]

Thanks for the reply :thumbsup:! First answer to the various threads I've made about this question that has made sense.

Unfortunately, the memory tab under CPU-Z is completely blank. I noticed that issue quite a while ago, but didn't really think much of it before. I'll probably ask about that on the CPU-Z forum when their server comes back up.

 

[JustaGeek]

You might want to try a different version of CPU-Z.

Alternatively, I would recommend Everest. It is not free, but it comes with a 30-day trial, and you might just like it. An excellent tool with the most complete information about your system, both Hardware and Software.

http://www.lavalys.com/

Good luck!

 

[wittangamo]

To answer the other parts of your question, there is no penalty to run your ram asynchronously. If you'll test it with a benchmarking program like SiSoft Sandra, you'll find your bandwidth scores are higher and your latency lower -- both good things -- when the ram is running at its rated speed rather than underclocked (as it would be at 1:1 in your system.) And 1.84V is not a problem.

You might also want to download and run MemTest just to assure yourself the memory is stable and error free at its rated speed. Chances are it could run a lot faster and take a bit more voltage if you wanted to push it. (Couldn't resist, I'm a relapsed overclocker with no self-control.)

 

[AmberClad]

Originally posted by: wittangamo
You might also want to download and run MemTest just to assure yourself the memory is stable and error free at its rated speed. Chances are it could run a lot faster and take a bit more voltage if you wanted to push it. (Couldn't resist, I'm a relapsed overclocker with no self-control.)

Yep, I just ran the series of recommended MemTest diagnostics from that thread in the OC/CPU subforum. No errors after completing a decent number of passes. I probably should have run MemTest when I first put the build together, but I kept putting it off because I didn't have any stability problems. Good to know for sure either way though.