667MHz DDR2 RAM being detected at 533MHz

[AlbertDong]

Recently took delivery of new PC, I had specced 667MHz RAM in an ASUS P5NSLI motherboard alongside an Intel C2D 6600.

POST reports memory is running at 533MHz, BIOS is setup to auto detect memory speed.

So - although the maunfacturer insists it's 667MHz RAM have I been sold 533MHz. Or...do I have to manually enter RAM timings and forego Auto detection?

If manual timings what should I be entering here? Alternatively am I making a mountain out of a molehill here and is the performance difference between 533MHz and 667MHz minimal / barely noticable?

Thanks for any help.

 

[evongugg]

Yes, the settings of your motherboard are correct at 533 MHZ.
Your 667 MHZ memory is running at the proper speed for your processor: 533 MHZ.

 

[bydesign]

While what you said is true it didn't answer his question clearly. In most cases you need to manually set the memory to the correct speed and timings of the chip.

 

[AlbertDong]

Thanks for quick response......makes sense now that you mention it as FSB is 1066MHz, however I suppose where my confusion lies is why bother fitting 667MHz RAM at all? Does this provide headroom for overclocking, does the CPU see any benefit to having 667MHz capable installed RAM unless I start to overclock?

Admittedly I've moved away from the home build and overclocking scene ( last one I did was an original Athlon based system i.e. the old slot interface ) so some of these maybe stoopid questions! Thanks for patience.

 

[Talon]

Adjust timings/voltages etc manually if you need to. Its not an uncommon problem. It doesn't mean the Ram is rated improperly or anything. For the specs of your specific Ram either look at packaging, some have a sticker on the stick itself or manufacturers website for specs to set it to.

 

[TurdBurglar]

There is often a setting in the bios called a memory multiplier or divider. Yours seems to be currently set to 2 (266 x 2=533). If you adjust it to 2.5 your RAM would run at 667 (266 x 2.5=667). Don't mean to insult your knowledge. Just trying to help.

 

[The_OGS]

why bother fitting 667MHz RAM at all? Does this provide headroom for overclocking?

Yes.
The Core2 CPU requires ~8.4GB/s memory bandwidth.
PC2-4200 memory @ 266MHz (533DDR), which is the same speed as the Core2 FSB, is said to run synchronously or 1:1 ratio. It provides 4.2GB/s bandwidth. This memory in dual-channel (128-bit) mode will give 8.4GB/s bandwidth, precisely matching the Conroe CPU.
The memory you describe is PC2-5400 rated for 333MHz (667DDR). This memory is being run synchronously 1:1 by your mobo. At this speed, which is below the memory's maximum rating, it will run 'tighter' memory latency timings at a nice low stock memory voltage of ~1.8-1.9V.
It's all very conservative and ensures that your stuff is compatible and your rig will always start right up, no problem.

does the CPU see any benefit to having 667MHz capable installed RAM unless I start to overclock?

Basically yes, with this memory @ 1:1 you can now increase your FSB from 266MHz to 300 or even 333MHz, which is the memory's maximum.
To continue to increase your FSB to 400MHz (1600QDR) you would require PC2-6400 memory, rated for 400MHz (800DDR).
Note: the PC2 number always indicates bandwidth, ie. 6.4GB/s for PC2-6400.
I run my FSB @ 300MHz giving 300 x 8 = 2.4GHz CPU speed.
My memory therefore runs @ 300MHz (600DDR) even though it is rated for 800DDR.
While the maximum rated memory speed will be achieved with ~2.2V memory voltage, running the memory at the lower (synchronous) speed requires less voltage as mentioned, and can deliver tight 3-4-4-10 timings too.
It is possible to run other 'asynchronous' ratios, which must be manually set:
4:5 ratio gives 667DDR with stock FSB; 2:3 gives 800DDR speed.
This memory bandwidth, in excess of the CPU bandwidth, can show a small performance increase in benchmarking - but mostly in memory bandwidth benchmarks, LoL.
The 4:5 ratio is not so good. If you have DDR2-667 memory you should run 1:1, maybe increase FSB to 300MHz, and there you go.
If you have DDR2-800 you could run 2:3 ratio, but this assumes stock FSB - if you OC your CPU you will quickly be returning to synchronous 1:1 anyway, heheh...
For most Core2 people I believe DDR2-667 is the best choice!
DDR2-533 leaves absolutely no wiggle room at all, and DDR2-800 is more expensive...
I bought the pricey OCZ DDR2-800 as more of an investment (it is a popular AMD SocketAM2 memory speed) and it will also run very good tight timings at slower speed like I said.
So does this make more sense to you now? I hope this helps,
Regards

 

[The_OGS]

There is often a setting in the bios called a memory multiplier or divider. Yours seems to be currently set to 2 (266 x 2=533). If you adjust it to 2.5 your RAM would run at 667 (266 x 2.5=667). Don't mean to insult your knowledge. Just trying to help.

The Burglar is trying to say the same thing in a different way (different mobo).
Various mobo brands will describe the FSB to memory ratio differently, and have varying ways to set it...
But 266:333 is always 4:5, and 266:400 is always 2:3 ratio.
And of course 266:266 (or 300:300 etc) will always be 1:1 or synchronous,
L8R

 

[powerbaselx]

Recently took delivery of new PC, I had specced 667MHz RAM in an ASUS P5NSLI motherboard alongside an Intel C2D 6600.

POST reports memory is running at 533MHz, BIOS is setup to auto detect memory speed.

So - although the maunfacturer insists it's 667MHz RAM have I been sold 533MHz. Or...do I have to manually enter RAM timings and forego Auto detection?

If manual timings what should I be entering here? Alternatively am I making a mountain out of a molehill here and is the performance difference between 533MHz and 667MHz minimal / barely noticable?

Thanks for any help.

Despite your memory is 667MHz "compatible", what counts is the FSB speed. The 667MHz means you can manually increase the FSB speed (somehow as written in the later posts here) to reach that speed (instead of default 533MHz). Since you have an Intel system (not extreme) this means you'll increase also the CPU speed as well since also the CPU multiplier is fixed in Intel CPUs.

 

[TurdBurglar]

The Burglar is trying to say the same thing in a different way (different mobo).

That's true. I was speaking as if the OP had a Gigabyte 965P-DS3. I am unfamiliar with his ASUS board, but it looks like you covered the other way dividers are listed in the bios.

 

[AlbertDong]

Guys - that's brilliant, things make more sense now. Thanks for your help....Albert D

 

[Bozzvegas]

The OGS! Just had to say great reply buddy guys like you make these forums great!

 

[Mondoman]

This post may help clarify some of the marketing:
http://forumz.tomshardware.com/hardware/modules.php?name=Forums&file=viewtopic&p=1249881#1249881

This review provides some real test data on running benchmarks and real apps with RAM at different speeds:
http://forumz.tomshardware.com/hardware/modules.php?name=Forums&file=posting&mode=quote&mode2=1&p=1432162