Sign in with
Sign up | Sign in
Your question

Please explain the connection between FSB and RAM speed. Very Confused

Last response: in Overclocking
Share
February 16, 2008 12:23:55 PM

I'm, planning a new build with an E2160 processor.
I understand that it runs at a default FSB of 200 and multiplier of 9. Therefore 200x9=1800MHz
Now if I overclock that FSB to 333 I get ~3000MHz (2997MHz exactly).

I know that overclocking the FSB will increase the RAM speed as well on Intel chipset motherboards.
Am I right in thinking that with that 333FSB, my RAM will be running at ddr2 666 speed?

To take a step backwards right now, if running at the default FSB of 200, this means my ram will be running at ddr2 400 speeds? But say I have ddr2 800 RAM. So I set the RAM to 800 in the BIOS settings, is it running at 800 even though my FSB is only 200? I get this is called "asynchronous" timing, when the the FSB and RAM speeds don't match.

The main reason I guess I'm confused is that all the overclocking guides I've read mention that you should set your RAM speed down low when upping the FSB, so as not to push the RAM too hard in the early stages, because the FSB and RAM speeds are linked.

But why does this matter if I can just set my ddr2 800 to 800 in the BIOS, and gradually up my FSB to 333? Won't my memory just stay at 800?

?Please Help. ***Very Confused***?
February 16, 2008 12:39:28 PM

For the ram, it all depends on the multiplier you choose for it which depends on the board. A 2x multiplier or 1:1 (because DDR2 is dual pumped) will be synchronous speeds running at the same speed as the FSB
For example at 200 * 2 = 400 ram speed or 333 * 2 = 667 (little off so its 667)

Now depending on the motherboard they will offer other fractions/multipliers. For me I have a 2.4, 2.5, 3.0 etc. This is if you want to run in asynchronous modes. Use this if a) you want to overclock your ram or b) your FSB is low and your stock setting for your ram is higher and you want to increase it.

So at a 333 FSB, in synchronous mode the ram will be 667. If you want you can increase the multiplier to 2.4 (not sure the fraction) to raise it closer to your stock 800 speeds.

Atm I have a 310 FSB and running a 2.4 multiplier to get 775 ram
February 16, 2008 1:03:28 PM

I kind of knew about the multiplier, but am confused in this case as one of the boards I'm looking at, Biostar 965PT, doesn't appear to have a memory multiplier setting, only ram speeds 533, 677, 800. Would the board perhaps auto set the multiplier based on the speeds that you choose?

Other boards I'm looking at are ASUS P5NE-SLI, and ASUS P5K. I'm not too sure if they have a memory multiplier option either. Heading off to Asus.com to find out...
Related resources
February 16, 2008 1:22:30 PM

Asus's website wasn't very helpfull, or I don't know where to look. I even downloaded the manual but I can't find mention of a Memory multiplier or anything that looks similar on the P5K.

http://www.xbitlabs.com/articles/mainboards/display/asu... Here's a review of the board showing its BIOS setings, Can you spot the memory multiplier in there? I can't.

Also I've heard that P5NE-SLI, as it's an nForce chipset, runs your FSB and RAM at independant timings. Is this correct? How does it work out?
February 16, 2008 1:52:38 PM

I would only get an Nvidia chipset if you want/NEED SLI. Otherwise get a P35 board. The Gigabyte P35-DS3L is a good overclocking board and has multiplier options.

On the Bios settings I see the frequency setting but they left it on auto.
February 16, 2008 2:20:26 PM

I see the frequency, that would be like 533, 667, 800 etc? Standard ddr2 speeds as far as I know.

I still don't understand, say if my FSB is set at 333, and I set my mem frequency to 800, will it just work like that?

I have it in my head that one MUST somehow change a setting that actually refers directly to memory multipliers. Is it just set out differently in different BIOSes or something?
February 16, 2008 2:36:53 PM

BigWoop said:
I see the frequency, that would be like 533, 667, 800 etc? Standard ddr2 speeds as far as I know.

I still don't understand, say if my FSB is set at 333, and I set my mem frequency to 800, will it just work like that?

I have it in my head that one MUST somehow change a setting that actually refers directly to memory multipliers. Is it just set out differently in different BIOSes or something?

I suppose your motherboard fsb is unlinked with the ram speed. Just set it to your preference and don't worry about the multiplier.
February 17, 2008 12:44:34 PM

Evilonigiri said:
I suppose your motherboard fsb is unlinked with the ram speed. Just set it to your preference and don't worry about the multiplier.


As far as I know this is not the case with 965 and P35 chipsets, only nForce 680i/650i, correct?
Also, I haven't actually got any of these boards, I'm just trying to find out what's best for my needs.

I am leaning now towards Asus P5K, as it is crossfire, and I'm planning on getting HD3850 for my build.

Still not anywhere near 100% sure what's going on regarding the memory/fsb connection issue, but I think I'm learning more...
February 17, 2008 12:46:15 PM

The P35 chipset is not Crossfire ready. The X38's are.

I dont get your problem, why not get the board and then see what the settings are. I can tell you the Gigabyte P35-DS3L us a multiplier...
February 17, 2008 1:27:58 PM

Silverion77 said:
The P35 chipset is not Crossfire ready. The X38's are.

I dont get your problem, why not get the board and then see what the settings are. I can tell you the Gigabyte P35-DS3L us a multiplier...


Well according to Asus the P5K is Crossfire ready...http://www.asus.com/products.aspx?modelmenu=2&model=163... this is correct as I quite like the board, not as a fashion statement or anything, but it's within my budget, and has most everything I want.

I don't specifically need Crossfire, but I am almost certainly getting HD3850. So It might be a good idea for the future.

It basically looks like I will just have to get it though and see how it works out. I just don't want to blindly wander in and come out with the wrong choice is all, regarding the whole overclocking thing, as I'm very new to it. The memory multiplier issue just really confuses me for some reason.



February 17, 2008 1:36:45 PM

O I see....it has a 4x slot......eh, I wouldnt really call that crossfire, that 4x slot will inhibit the power of the second card. Also usually by the time you get a second card, the next best thing is usually better. Like the 3870's. 2 in crossfire sounds great, but now the 3870x2 is out that beats them and is the same price.

Overclocking on the memory, Asus boards I believe us fraction multipliers. But in those terms any P35 Asus board or Gigabyte board is good.
February 17, 2008 1:57:35 PM

I'm sure 4x Isn't great, and I agree that something better will be along by the time I get a second. I probably will never get a second HD3850. It just makes more sense to me to get a crossfire rather than nForce with sli. Just in case I DO want another card.

I was looking at 650i chipsets because their RAM and FSB are unlinked, removing the memory multiplier issue. But then I thought there's not mutch sense in having a SLI board with an ATI GPU.
February 17, 2008 3:31:35 PM

Ooooo, thats what you were referring to. Yea, go with an Intel chipset (mainly P35)

Asus and Gigabyte are the best. P5K I've heard is good and I have the Gigabyte P35-DS3L which is nice
!