RAM speeds related to FSB

CRE · 16-May-04, 04:45 AM

Hey guys, I'm werking on a log/worksheet of sorts and was wondering about this:
When you're running PC3200 (DDR400) on an FSB running at (lets say) 133MHz, Does the RAM run at 266MHz (133MHz * 2) or is there a positive multiplier which allows it to actually run @ 200MHz (or depending how you look at it 400MHz)?

Iateronmly · 16-May-04, 04:50 AM

Yes some motherboards allow you to run the memory faster than the CPU's FSB but it's rather pointless. Keep them matched up and see if you can tighten your timings instead.

CRE · 16-May-04, 05:13 AM

Thanks Lateronmly, I figured as much. Unfortunately, I can't get my timings any tighter than 2.3.3.6.T1 at any speed. I'm currently runnin @ 392MHz with a 157MHz FSB. I don't know if it's the RAM of the SiS chipset my board has.

Anyway, that's not a big deal, I just wanted to confirm that even though a mobo's BIOS may state a 1:1 ratio it's not exactly the case. For example I'm running a 157 FSB and my RAM's clocked to 392. That'd be a 4:5 ratio (CPU:RAM). Do some BIOS versions actually list these for the true ratio they are?

Iateronmly · 16-May-04, 05:25 AM

Quote:

Originally Posted by CRE


	Thanks Lateronmly, I figured as much. Unfortunately, I can't get my timings any tighter than 2.3.3.6.T1 at any speed. I'm currently runnin @ 392MHz with a 157MHz FSB. I don't know if it's the RAM of the SiS chipset my board has. Anyway, that's not a big deal, I just wanted to confirm that even though a mobo's BIOS may state a 1:1 ratio it's not exactly the case. For example I'm running a 157 FSB and my RAM's clocked to 392. That'd be a 4:5 ratio (CPU:RAM). Do some BIOS versions actually list these for the true ratio they are?

No two seem to be alike that I've gotten. On this current board I can set speed limits for my ram for example which forces the divider to the closest but not exceeding. (like I can make my DDR400 Geil run at a max of 266..... no idea why I would but I can). Some like you said state 1:1 4:5 and such. But as far as your current settings it doesn't make sense, if it says 1:1 it isn't ....

But I'm not suprised by anything that happens when dealing with Sis and Via chipsets not doing what they claim to do. Such as this lovely mobo I have now that has CPU FSB adjustment in the bios that don't do jack.

CRE · 16-May-04, 05:34 AM

Oh, don't get me wrong, my current mobo states the speed, not the ratio. I just wanted to know for a little worksheet I'm working on.... to make sure to be thorough.

16-May-04, 04:45 AM		#1 (permalink)
CRE Apex Tech Maniac Supreme	RAM speeds related to FSB Hey guys, I'm werking on a log/worksheet of sorts and was wondering about this: When you're running PC3200 (DDR400) on an FSB running at (lets say) 133MHz, Does the RAM run at 266MHz (133MHz * 2) or is there a positive multiplier which allows it to actually run @ 200MHz (or depending how you look at it 400MHz)?

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16-May-04, 04:50 AM		#2 (permalink)
Iateronmly Smooth Operator	Yes some motherboards allow you to run the memory faster than the CPU's FSB but it's rather pointless. Keep them matched up and see if you can tighten your timings instead.

16-May-04, 05:13 AM		#3 (permalink)
CRE Apex Tech Maniac Supreme	Thanks Lateronmly, I figured as much. Unfortunately, I can't get my timings any tighter than 2.3.3.6.T1 at any speed. I'm currently runnin @ 392MHz with a 157MHz FSB. I don't know if it's the RAM of the SiS chipset my board has. Anyway, that's not a big deal, I just wanted to confirm that even though a mobo's BIOS may state a 1:1 ratio it's not exactly the case. For example I'm running a 157 FSB and my RAM's clocked to 392. That'd be a 4:5 ratio (CPU:RAM). Do some BIOS versions actually list these for the true ratio they are?

16-May-04, 05:34 AM		#5 (permalink)
CRE Apex Tech Maniac Supreme	Oh, don't get me wrong, my current mobo states the speed, not the ratio. I just wanted to know for a little worksheet I'm working on.... to make sure to be thorough.