Overclocking RAM: Why?

MichaelD

Lifer
Jan 16, 2001
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Your front-side-bus (FSB) is the "pipe" that goes b/t your CPU and the system memory. The bigger you make that pipe, the more information can pass b/t the RAM and the CPU.

Oversimplified, but the theory is correct.
 

DAPUNISHER

Super Moderator CPU Forum Mod and Elite Member
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Aug 22, 2001
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Originally posted by: Bachopoet
If the mobo supports 333MHz FSB, and the RAM is 333, is it possible to widen the pipeline?
yes.........
 

MichaelD

Lifer
Jan 16, 2001
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If you have the appropriate RAM, it is possible to go past 333MHz FSB. The 333 you're referring to is actually the DDR (Double Data Rate) rate.

133MHz=266MHz DDR (use PC2100 ram)
166MHz-333MHz DDR (use PC2700 ram)
200MHz=400MHz DDR (use PC3200 or PC3500 ram)

See, you can have a stick of PC2700. It is rated to operate reliably, all day long at 166MHz. If you buy a no-name stick then you probably won't be able to go much past 166MHz. But a brand name stick of PC2700 like Crucial or Corsair will most probably go past 166MHz...possibly up to 180 or more.
 

MichaelD

Lifer
Jan 16, 2001
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The chipset on the motherboard determines the maximum front side bus speed. Broadly speaking, all motherboards these days, both AMD and Intel based to up to at least 200MHz. :
 

Bachopoet

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Sep 3, 2002
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So if a motherboard says it supports 266FSB, then it really supports DDR at 533MHz, or are the mobo's stats misrepresented as well?
 

Bachopoet

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Sep 3, 2002
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Here's the combo I'm looking at. I'm looking at the FIC AN17 mobo with AMD 2000+ and 512PC2700
MWave Linky!
Is that a good match? Overkill on either side, memory or mobo?
 

MichaelD

Lifer
Jan 16, 2001
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A few things:

1. 533MHz is a quadruple DDR spec for a Pentium 4. P4 motherboards operate at a 4x data rate. They used to use memory that ran at 100MHz (400MHz 4DDR) but recently started using chipsets that supported 133MHz memory (533MHz 4DDR)

2. No matter whether you go AMD or Intel DO NOT skimp on memory; you'll regret it big time. Get a nice stick of Crucial PC2700 or for a few dollars more, a stick of Corsair XMS3200 CAS2 if you intend to overclock.

3. Right now, the boards to get are NForce2 chipset-based boards. The Asus 87N8X or Epox 8RDA+ are the ones your want. A KT333 or KT400 (Via chipset) board is good as well. Read the Motherboard forums; lots of helpful info there. FIC motherboards are just not up to par, IMHO.

4. KT333/KT400 boards have a 1/5 PCI divider. (Overclocking is more complicated than just upping FSB frequencies :)) When you raise your FSB speed, you also raise the AGP and PCI bus speeds. Your AGP card is supposed to operate at a 66MHz bus speed, your PCI cards run at 33MHz. For every 2-3 MHz you raise you FSB speed, your AGP/PCI speeds go up by 1MHz. So, at say 150MHz, your AGP/PCI busses are way out of specification. Some cards can run out of spec, others, including HDs will crash. Not good.

5. On KT333/KT400 boards, the 1/5 divider kicks in at 166MHz (333DDR/PC2700 speed). So at 165MHz your busses are out of spec, but at 166MHz they are back perfectly at 33/66MHz respectively.

6. NForce2 boards have the AGP and PCI busses locked at proper speeds REGARDLESS OF WHAT YOU SET THE FSB AT! So, that's one BIG overclocking problem taken care of right off the bat. In the past, your CPU and Memory might be able to take a 150 FSB, but your NIC or your videocard might not.

Hope this helps.