Frontside Bus

[tburns0112]

I don't understand what part of my Intel chipset controls FSB speed. My chipset is running at 800mhz FSB. The 925XE chipset documents say the chipset "supports" a 1066mhz or 800mhz FSB speed. My new PC has an ASUS P5402-E premium motherboard. The Intel chipset is running at 3.4 mhz. I've read all of Intel's data but can't figure out what chip(s) control the FSB speed. Can someone clue me in?
Thanks Tom

 

[o1die]

If you're reading 3.4, no need to worry. The actual setting for cpu fsb in the bios is 200 for 800 speed. You may find it in the "frequency and voltage control" section.

 

[jammydodger]

Firstly your 'chipset' does not run at 3.4Mhz, it is your CPU that runs at 3.4GIGAHERTZ (as opposed to Megahertz).

The front side bus of your motherboard is determined by your CPU (Unless you overclock). The first P4 processors used a 400Mhz FSB, then 533MHz, then 800Mhz and the very top of the line CPU's use 1066Mhz FSB.
Your motherboard detects the FSB your CPU uses and then defaults to that speed.

Your CPU uses a 800Mhz FSB and so cannot run at 1066Mhz without seriously overclocking the chip (the clock speed of a chip is determined by multiplying the FSB with a number built into the CPU).

 

[mozzartusm]

Hey dude its P5AD2-E-Premium :lol: Ive got this same mobo. Give me your system specs and I will be able to help you with your questions.

Intel P4 550(3.4)<font color=red>@4.2 posted 4.8</font color=red>
ASUS P5AD2-E-Prem
Ballistix PC2 5300@<font color=red>DDR2 780</font color=red>
ATI Radeon X800XL <font color=red>459/609</font color=red>
TT 680W PSU

 

[mozzartusm]

Is your CPU a 550 or a 650?

Intel P4 550(3.4)<font color=red>@4.2 posted 4.8</font color=red>
ASUS P5AD2-E-Prem
Ballistix PC2 5300@<font color=red>DDR2 780</font color=red>
ATI Radeon X800XL <font color=red>459/609</font color=red>
TT 680W PSU

 

[Crashman]

The bus speed is determined by the motherboard after reading what it's supposed to be from the CPU. You have an 800 bus CPU, your board sets the chipset to 800 bus. It can't change it to 1066 bus because the CPU has a fixed multiplier, and the higher bus speed would overclock the CPU speed too far.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[mozzartusm]

His multiplier can be manipulated with that Mobo. Mine is stock 17 but with my ASUS mobo it will also run at 14 which is where I keep it.

Intel P4 550(3.4)<font color=red>@4.2 posted 4.8</font color=red>
ASUS P5AD2-E-Prem
Ballistix PC2 5300@<font color=red>DDR2 780</font color=red>
ATI Radeon X800XL <font color=red>459/609</font color=red>
TT 680W PSU

 

[Crashman]

Don't mention that here because it's only going to confuse him: The guy is practicing under the assumption that all available bus speed is a matter of motherboard support, with no consideration needed for the CPU type. Giving him advice on overclocking techniques is only going to confuse him more.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[mozzartusm]

I want giving him advise on Overclocking. I just thought that you missed the type mobo he is using.

Intel P4 550(3.4)<font color=red>@4.2 posted 4.8</font color=red>
ASUS P5AD2-E-Prem
Ballistix PC2 5300@<font color=red>DDR2 780</font color=red>
ATI Radeon X800XL <font color=red>459/609</font color=red>
TT 680W PSU

 

[tburns0112]

My CPU is a 650. You guys have helped me out a lot. Now I see the processor chip determines the FSB rate and speed. I thought that was imbedded in the "chipset". My last PC is a 200mhz Pentium so you can tell what cave I just crawled out of. I had a few extra bucks so I bought a box that was pretty much a screaming machine. All I do is some graphics work and surf the web and this PC moves data so fast I'm in awe. Thanks again for your help.

 

[tburns0112]

Thanks for your help. I was confused about the roles of the chipset and cpu/processor in FSB speed. I think I'm seeing daylight. I'm not going to overclock because of what I perceive as heat and potential damage to my PC. Instead I bought a fast harddrive (WD 10k rpm Raptor) and the fastest chipset and cpu combo that I could get within my budget. So far I'm amazed at the speed of data movement. Thanks again........

 

[mozzartusm]

As long as you keep the heat under control you have one very nice system. I have the 3.4 (550) model which is a hotter CPU. If you ever need anything post your questions or send me a PM.

Good luck

Intel P4 550(3.4)<font color=red>@4.2 posted 4.8</font color=red>
ASUS P5AD2-E-Prem
Ballistix PC2 5300@<font color=red>DDR2 780</font color=red>
ATI Radeon X800XL <font color=red>459/609</font color=red>
TT 680W PSU

 

[Crashman]

Nope, it's that he doesn't seem to have a grasp on how the motherboard's bus speed selection is appropriate to whatever the CPU was assigned by the manufacturer.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[Crashman]

Certainly. I'll just do a brief explanation:

Back in the Pentium III days we didn't have Double Data Rate (DDR) or Quad Data Rate (QDR) busses, nor AMD's HyperTransport bus. So multipliers were easy: A PIII 800E ran at a multiplier of 8x, 8x100=800. A PIII 800EB ran at a multiplier of 6x, 6x133=800. So the "B" in those days designated the higher 133MHz bus speed. The CPU had 2 pins that were either connected or not, the board would read those two pins and determine which bus speed was appropriate.

AMD came out with a Double Data Rate bus called the 200MHz bus. It was actually 100MHz, where 100MHz represents the electrical frequency, but 200MHz represented the rate that data was cycled. DDR cycled data twice per clock cycle. DDR SDRAM is based on the same principle.

Intel followed with a Quad Data Rate bus, which cycled data at 4x the frequency of the bus. So now we get up to current Intel technology:

18x100=1800, the P4 1.8A had a bus speed of 100MHz, with a data rate of 400MHz, so it was called a "400MHz" bus.

18x133=2400, the P4 2.4B had a bus speed of 133MHz, with a data rate of 533MHz, so it was called a "533MHz" bus.

18x200=3600, the P4 3.6E has a bus speed of 200MHz, with a data rate of 800MHz, so it's called an "800MHz" bus.

Notice all three of those had the same 18x multiplier, and that the 18 was multiplied by the electrical frequency of the bus, not the data rate. All 3 had the multiplier "locked", it couldn't be changed. Changing the bus speed would therefor change the CPU speed.

Believe it or not there are a few boards that can support all 3 of those processors, and the way it knows the difference is still by detecting which of 2 pins are connected or disconnected.

Intel has very few 1066 bus processors (266MHz clock, Quad Data Rate). If you put an 800 bus processor on a 1066 bus capable board, it will choose 800 bus rather than 1066 bus.

Now if that sounds like marketing trickery, consider AMD's 2000HT bus...

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[mozzartusm]

They lock the multiplier by making a laser cut on the CPU, correct? I saw the article that showed how to fix the cut so that the multiplier would be unlocked but i think that was on an AMD. Has anyone been able to do the same on the newer Intels?

Intel P4 550(3.4)<font color=red>@4.2 posted 4.8</font color=red>
ASUS P5AD2-E-Prem
Ballistix PC2 5300@<font color=red>DDR2 780</font color=red>
ATI Radeon X800XL <font color=red>459/609</font color=red>
TT 680W PSU

 

[Crashman]

As far as I know, Intel blows bridges.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>