Question about FSB

[Guest]

Ok, just a bit of uncertainty I think. Or maybe I am completely wrong.
Anyway:

The CPU I am thinking of getting is a Athlon C type which is 266FSB. I was gonna get some PC2400 ddr ram which runs at 150MHz (that right?)
So I will have to increase the FSB of the motherboard to 150MHz, otherwise, if i leave it at 133MHz, the ram will be the same as PC2100 ram (correct?)

Anyway, so would I have to unlock my cpu so that i didn't need to overclock that?

Also, what does the 266FSB of the CPU mean? what is running at 266MHz?


You can probably see that I am quite confused. Any help would be appreciated

 

[camieabz]

266MHz FSB = 133MHz FSB DDR bandwidth.

<b>
"Now drop your weapons or I'll kill him with this deadly jelly baby."
</b>

 

[Guest]

What about the RAM. If I buy pc2400, do I need to increase the FSB of my motherboard to 150MHz for the RAM to operate at pc2400 level?

 

[camieabz]

Not sure. Makes sense.

<b>
"Now drop your weapons or I'll kill him with this deadly jelly baby."
</b>

 

[Guest]

Ok, I'd guess it is correct too.

 

[Guest]

I am not positive, but I am almost positive. The PC150 means the RAM is rated to safely run at PC150. That is maximum, it doesn't need to run at that speed, however. If your board is 266DDR, which is PC133, you can put the chip in there, and it will definitely run at PC133, cuzz it is rated at PC150 and you are only running it at 133. PC150 is if you want to overclock, then you can run up to PC150 which is 300 DDR. Get it? Can someone back me up or prove me wrong here?

 

[Unolocogringo]

you got it right.And yes to get pc2400 performance out of your memory you would have to run it at 150 fsb.Running it at 133fsb will give you PC2100 performance.If you might get the overclock bug get the PC2400 and have fun.

I aint signing nothing!!!

 

[Mordy]

RE: >>If I buy pc2400, do I need to increase the FSB of my motherboard to 150MHz for the RAM to operate at pc2400 level

Yes.
<A HREF="http://www.mushkin.com/cgi-bin/Mushkin.storefront/3b701f2711afa66e2740c0a80102067a/UserTemplate/25" target="_new"> About PC2400 </A>

-Beer! Good!
-James Hetfield

 

[kevstev]

that 150 rated stuff essentially means that it is rated to be run at faster (overclocked) speeds. I am sure of this.
-k

I pledge allegiance, to the flag, of the Corporate Republic of America...

 

[kevstev]

I see that I did not completely answer you. the 266mhz means that your bus is running at 266mhz. This means that data is being transferred 266 million times across the bus. now Athlon busses (plural bus = busses? bus? busi?) are called "double pumped" meaning that they transfer data at both the leading and trailing edges of a clock cycle. so in actuality, the front side bus is running at 133 mhz. The athlon fsb is 64 bits wide, meaning there are 64 lanes for bits to travel down, so the total bandwidth delivered is 266,000,000 * 64 bits /sec = 1.56 GB/s. You would have to overbus your FSB to 150 mhz, or an effective 300 mhz (~1.75 GB/s throughput) to get your money's worth out of your RAM. now overbussing by that amount is about 12% or so, meaning your processor would run about 12% faster too. This is a method that was long used on Pentium II's and III's on the BX motherboards as the multiplier was locked. Generally speaking, RAM can be the weakest link when overbussing, but also remember that you are overclocking the PCI/AGP bus as well, and modems/soundcards/graphic cards that are already pushing performance limits have a chance of malfunctioning. This was all taken off the top of my head, so some of my figures may be slightly, off but the concepts remain the same.
-k

I pledge allegiance, to the flag, of the Corporate Republic of America...

 

[macodi]

..and yes you can run the FSB below 150mhz and the PC2400 RAM will work fine. Even with lowly PC2100 RAM your problem will most likely be with PCI or AGP devices before the RAM chokes if you set to 150 FSB. IMHO.

-----------------------------------------------------------
We don't need no stinkin' badges.

 

[Guest]

What about the RAM. If I buy pc2400, do I need to increase the FSB of my motherboard to 150MHz for the RAM to operate at pc2400 level?

this is not <i>entirely</i> the case as normal 2100 DDR is rated at cas-2.5 at 133MHz(266 DDR) the 2400 is rated at cas-2, although most 2100 sticks will do cas-2 at 133(266), the flashy 2400 should take all you can throw at it at that speed (133).

If you wan't to overclock the FSB to 150(300 DDR), you will probably have to unlock you CPU to drop the multiplier, as 12% is quite a big overclock. Although your athlon <i>may</i> handle it (if your cooling is good and you have Vcore adjustments) you will have trouble knowing what is failing as you push the clock speed up.

remeber FSB overclock effects PCI/AGP as well as RAM/CPU.

"Rehab is for quitters."

 

[Unolocogringo]

12% is not a big overclock these days. We are looking at 100% overclocks in quite a few instances.I personally overclock 55% daily. I can overclock 66%, but why push it.

I aint signing nothing!!!

 

[killall]

266mhz fsb = 2 x 133... pc2100 is pc 133/266 ddr... if you want to get the 2.4gig/sec bandwidth of the pc2400 you will need to overclock with fsb to 150/300...

if in doubt blame microsoft...

 

[knowan]

The important thing to remember here is that if you are overclocking your front side bus, you are also overclocking your CPU, you chipset and you PCI/AGP slots. Unless your components are top of the line, it is likely that one of your PCI cards will fail long before you reach 150 mHz. Your Ram is rated to run at this speed, you processor would most likely be able to run this fast (but it would take alot of tweeking and cooling), you chipset should be fine so long as it is cooled. Your best bet is to yank all the cards first, then overclock as high as you can go and only then add your cards back in one at a time. With a bit of luck they'll all run fine.

Your motherboard isn't the greatest for overclocking though. I don't know if it will let you go this high. Comments anyone?