Memory bus speed question

[fenix]

A current repair project found a dead DIMM. The bios setup states that the external bus speed is 133 MHZ, so I assumed that I could use PC-133. (wrong !!) This computer (dell gx-110 PIII/667) only supports PC-100 according to Crucial and folks in a dell forum. But one question not answered is what controls or sets the memory bus speed ?

I would guess that it either has it's own clock crystal somewhere on the board, or maybe it's a crystal embedded in the northbridge chip, or maybe some kind of multiplier that reduces speed instead of multiplying it, also maybe in the chipset?

just curious, thx

 

[ski]

The MB's chipset determines the bus speed.

 

[cdogg]

That is a bit strange. I can't say I've ever seen a motherboard that used a 133MHz frontside bus, but only supported PC100. Strange indeed!

One thing to note is that newer chipsets allow the frontside bus and the memory bus to run at separate speeds. So, just because the FSB runs at 133MHz, it's not always safe to assume that the memory bus runs identical.


~cdogg

"The secret to creativity is knowing how to hide your sources."
- A. Einstein

 

[ceh4702]

When the Motherboard is built its architecture is designed around a chipset that is possible of supporting a maximum Memory Bus Speed.

Sometimes a Processor selection will limit the bus speed even slower. An example of this may be using a Celeron in stead of a PIII etc. Even some PentIII support different Memory bus speeds depending on the processor selection.

Sometimes the Motherboard is designed for a slower bus speed even though the chipset will allow a faster speed. This is up to the implementor of the motherboard's Architecture.

Sometimes the BIOS limits the bus speed. Even though it is controlled by the BIOS, sometimes the BIOS has updates that support different speeds, or the BIOS Allows for overclocking by using stepping for the bus speed or memory speed/Voltage.

If you do not like my post feel free to point out your opinion or my errors.

 

[biohazzard72]

I'm running a Dell GX-110 733 Mhz with 512 Mb PC133 just fine. I think there is something in the BIOS that lets you specify the clock for memory bus.

 

[biohazzard72]

Update the chipset drivers.

 

[TigerFlight]

Well from my travels. I have used PC-133 in a PC-100 box. It just runs a 100. Here'ss a link!

http://www.thetechzone.com/articles/pc100_vs_pc133/

or

http://www.pcmech.com/show/reviews/268/

[sup]Tiger[/sup][sub]Flight[/sub]
Everyone has their two cents worth. Lets all try to donate our two cents and maybe we all can come up with a Dollars worth of advice!!!!!