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P5B with E6300@7x400 won't let me use Memory@667

X

xorxor

Junior Member
Hi,

using an Asus P5B (BIOS 0806) motherboard I was able to set the FSB to 400MHz to run my E6300 at 2.8MHz.

However, with this setting the lowest manual memory clock available from the BIOS is DDR2-800, which my DDR2-667 can not take (system won't boot). On the other hand, if I keep the memory clock setting at "auto" then the BIOS sets the memory clock to DDR2-533, which is a waste considering I have DDR2-667 (but it runs stable).

If I am not overclocking, the BIOS automatically chooses DDR2-667 which is correct.

Now I wonder: how comes with FSB400 I can not select a lower than DDR2-800 clock manually if the BIOS can obviously deliver this clock (namely when set to automatic)?

And how comes the auto setting is not using the correct DDR2-667 clock, but DDR2-533 when setting the FSB to 400?

Has anybody experienced this before?

Cheers,
XOR

PS: I am using 2x 1024MB DDR2 Aeneon PC5400 CL 5, PC5400/667
 
So you're on a 400Mhz FSB, and you want to run your RAM at 333Mhz (667Mhz DDR)? Unless something has changed, such is impossible and undesirable. With a Core 2 Duo, you want memory running 1:1 with the FSB (or higher), but they cannot be run on lower dividers (like the 939 A64s). If your RAM can't handle 400Mhz (800Mhz DDR), then i'm afraid you're possibly at the limit of your overclock (if you don't put more volts through the RAM).
 
Hi,

thanks for your reply!

Well, after some more reading I am also no longer sure if my memory is really running at only DDR2-533 with the FSB400. What made me think so was the boot message: "PC2-4200", but this may just be a missleading way of the BIOS to tell me the FSB : DDR2 clock rate is 1:1.

This would mean that I am running my RAM at DDR2-800 in fact. That would be a pleasant surprise since I did not have to change any voltages or timings and memtest86+ ran fine for hours.

Is there a tool to really check the current RAM settings (clock and timings)? I was running Linux so far, so I was not able to run CPU-Z.

I also wonder why manually selecting the lowest RAM clock (800) will fail, but selecting "auto" succeeds...


 
The memory will be running at 800MHz. The P965 chipset doesn't support dividers where the memory bus is slower than the FSB, the lowest ratio is 1:1. The bios message "PC2-4200" is misleading as it doesn't report the actual speed, but what the memory speed would be if you were on the default FSB.
 
Thanks, that makes me very happy! 🙂

However, I wonder what is so special about the "Auto" setting since setting the clock to "800" manually will not work. But that is just a question of curiosity...
 
There's a very good reason that setting your memory to run @ 800 manually doesn't work. It's because that speed is based on what your memory would be running with your FSB at stock, or 266, and your processor @ 1.86 Ghz. You were trying to run your RAM @ ~1200 DDR, in other words. Try 800, with your FSB @266, and it would work.
 
You are confusing dividers/ratios with actual RAM speed.

Your RAM does not run @ 533/667/800 unless you are running everything at stock.
533/677/800 are dividers.

Think of those ratios like this:

533 = 1:1 or RAM speed = FSB speed
677 = 4:5 or RAM speed = 1.25x FSB speed
800 = 2:3 or RAM speed = 1.5x FSB speed

So i'd suggest manually setting your RAM to 533 & the timings to:
5-5-5-15-6-42-10-10-10-10
You will likely have to up vdimm to keep them stable as you overclock, & eventually, they'll likely crap out.

Your CPU could do 3200 MHz for sure, but it's hard to say if your RAM will make it that far.
 
Thanks folks, for all you helpful hints!

I was now able to check what is going on with CPU-Z and you were right: with FSB 400 the RAM is clocked 1:1 as DDR2-800 (aka 400MHz). The boot message "PC2-4200" is just misleading.

I can also see that the BIOS has picked the following RAM timings for 800: 5-6-6-18 (the SPD suggests 5-5-5-15 for 667 - though the label on the DIMMS states 5-5-5-12).

I did not change any voltages. I just set the FSB to 400 and fixed PCI@33.33, PCIE@100. Everything runs smooth (2 x prime95 and memtest95 both run OK).

So it seems the DIMMS I got are running at 800 with ease:

2x 1024MB DDR2 Aeneon PC5400 CL 5, PC5400/667

(Aeneon is the low cost brand of Infineon as far as I know).

Thanks!
 
Yes, bummer: somehow I got a blank posting after typing all my text - it seems I need to switch off some "Greasemonkey" scripts as the yseem to interfere with this forum software ;-)
 
You could likely go into your bios & set things to 5-5-5-12, as 5-6-6 is rather loose.

But what i'd suggest is leaving it the way it is, & seeing how far you can get her 🙂

Your E6300 will do at least 3200 MHz if your RAM cooperates.

You'll need around 1.35-1.4V CPU vcore once you get higher, & your RAM would likely do a bit more if you bump it one or two steps above it's rated vdimm.
 
Thanks n7,

I may try to push the envelope once I have gained some confidence in the current OC. Right now I am already amazed how easy it was do get 50% more power out of the E6300...
 
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