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[Limedust]

I recently picked up an XP3000+ with the 333 MHz FSB. It is intended to run at 2.17 GHz. What I am seeing is that it is running at 1.768 GHz, which makes sense if the FSB is only running at 266 MHz instead of the intended 333 MHz.

The DDR RAM that I have is PC2100 (DDR266). I was under the assumption that the RAM bus and CPU bus that go to the Northbridge were separate, but the problem I am seeing would make sense if this were not true and the FSB is tied directly to RAM (and hence the reason I am only able to run the FSB at 133 MHZ, or 266 DDR). Can someone confirm this, and also back me in saying that if I were to install PC2700 (DDR333) into a my motherboard, and the MB was capable of running a FSB of 333 MHZ, then my CPU would then run at the intended full speed?

 

[Shogmaster]

With AMD, RAM is the key to clockspeed, along with the proper mobo settings. You need the PC2700 to reach the proper speeds of your CPU. With PC3200, you can try to overclock your CPU.

 

[Limedust]

How does the FSB route on the typical AMD mobo (schematically)? Is it tied directly to the CPU, RAM, and Northbridge? Or do both the CPU and RAM tie to the Northbridge and the clock setting is simply normalized to the lowest common denominator between CPU and RAM on autodetect?

A PC architecture chart would really help me out, but I can't find one now that I've gone looking.

 

[myzhi]

In most cases, the cpu speed is control by the FSB. What's your current FSB setting? Also, remember lots of MBs from FSB / memory ratios, like 1:1, 5:4, 3:2, and etc. Thus, the FSB could run faster then memory speeds.


Download cpu-z, and then, tells us what it says for cpu / memory tab. Important to look for "FSB" in cpu and "FSB : DRAM" in memory tab.

http://www.softpedia.com/public/cat/13/5/13-5-23.shtml

 

[Limedust]

It shows both the FSB and Memory being run off of a 136MHz (133MHz) clock, which tells me there is a single clock controlling both.

I am pretty sure both the main memory bus and the CPU FSB are independently connected to the Northbridge... it just appears that both busses are driven from the same clock source. I don't seem to be able to run both from a separate clock source, so it appears that the only way to run my CPU at the intended clock speed is to install DDR333 in place of the DDR266 that I have.

 

[myzhi]

If both are showing 133 mhz, it means your MB is currently running a 1:1 ratio. If your MB allows you to change it to 5:4 (in bios), then you can up the FSB to 166 mhz and still use your existing memory running at 133 mhz. If you can't change ratio, you must get PC2700 ram. Also, don't forgot to up FSB to 166 mhz if needed.

 

[Limedust]

I dug out my motherboard manual (Gigabyte 7VAXP), and there is this note listed:
FSB333 MHz only support DDR333 DIMM module.

As I thought. My motherboard doesn't allow separate FSB and Main Memory clock speeds. That stinks. Oh well, thanks for the assistance folks. It's been appreciated.

 

[Shogmaster]

My mobo has two sets of dip swtiches that control FSB and the multiplier clock respectively.

I'm running a 1.9Ghz Barton (2600+) that has 333Mhz FSB. I had to set the FSB to 166Mhz (333/2) and the multiplier clock to 11.5 by toggling the dip switches to predetermined patterns laid out in the mobo manual.

I also had to make sure that in the BIOS, the memory/FSB was set to 333Mhz. It was set to 266Mhz by default and I had to change it.

 

[Limedust]

I did try manually setting my FSB to 166MHz, which hung the system for the 20 second timeout before the BIOS reset itself to the safe default of 133. It appears that for my particular motherboard, both the FSB and main memory bus are run from the same clock source instead of having independant control.

 

[Shogmaster]

I did try manually setting my FSB to 166MHz, which hung the system for the 20 second timeout before the BIOS reset itself to the safe default of 133. It appears that for my particular motherboard, both the FSB and main memory bus are run from the same clock source instead of having independant control.

You have the same mobo that I do. We already told you that the RAM has to be PC2700 to get your Barton to clock properly. No way around it. Just spring for PC3200 since the cost is about the same as PC2700.