DDR and CPU clock speed.

[Lohr]

I'm new to DDR ram but a seasoned computer geek.

I have a brand new Giga-byte GA-7VRXP KT333 Motherboard and i just installed my Corsair CMX512-2700C2 ram. I have yet to upgrade my processor (ran outta money ). I'm still using my old thunderbird 1ghz that only runs at 100mhz FSB.

Here is my question:
Does the mhz of the DDR ram have to run at exactly 2 times the FSB of the CPU?

I set my RAM to run at 333mhz and my FSB at 100mhz. Windows XP blue screened on install. The only way i can get it to install is by setting my DDR ram to run at 200mhz, coincidentally, 2 times my FSB.

what i'm wondering is if this logic is correct, and i'm not doing anything wrong, and my hardware is working properly, then what the heck is the point of 333mhz DDR if the highest any AMD processor will run at is 133mhz FSB (making the DDR run at 266mhz).

Basically what i'm asking is - it seems to me that the DDR will only run at the FSBx2. am i wrong?

 

[Crashman]

Nah, it's a problem with your system, either the board, memory, or power supply, not living up to it's DDR333 rating.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

 

[Lohr]

i did some more research and came up with very little. however i did find a small tidbit on a respected website that mentioned synchronus and asynchronus RAM. It said tha some RAM is capable of running at a different frequency than the FSB and some is not.

MY old motherboard was a KT133 with PC133 ram in it. the processor was my old thunderbird 1ghz. The FSB was set for 100hmz and the RAM was set at 133mhz. it had a setting in the bios that allowed you to change it between synchronus and asynchronus.

so maybe my RAM jsut isnt capable of running asynchronus. it makes sense to me.

my only other problem is that now i need a CPU that runs at 166mhz FSB so i can fully use mt DDR333. i also need to read my manual some more to see if my board can run a 166mhz FSB. :/

 

[bum_jcrules]

Did you try setting the FSB higher?

<b>"If I melt dry ice in a bathtub, can I take a bath without getting wet?" - Steven Wright</b>

 

[Crashman]

Nope, that's not your problem. RAM doesn't know whether it's running sync or async, your problem is either that the ram won't run at it's specified value, your chipset sux, or there is something wrong with the voltage.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>

 

[Lohr]

ok...

hmm i got the best ram money can buy. recommaneded by THG btw. Got the fastest motherboard i could find. its a giga-byte, what i see to be a good brand.

i think i'll just call giga-byte and corsair about this and see what thier tech support says

i've got another question, me and my friend have argued about this for a while now:

My thinking: The FSB of any AMD motherboard can run at only 100mhz or 133mhz. The DDR ram can run at 200,266, or 333mhz. there is a switch on my motherboard that changes it between 100mhz and 133mhz FSB...so it makes sense to me that this is what sets FSB of the CPU - therefore the FSB is only 100 or 133

His thinking: The FSB of the motherboard is actually 200mhz and 266mhz, NOT 100/133.

can someone please sit down and explain to me exactly how FSB, DDR, and all of thier frequencies interract? if you dont want to, could you at least send me a link to somthing that does?

i'm just really confsued now!

oh and to answer "Did you try setting the FSB higher?"
no - my processor is an old thunderbird, it only runs at 100mhz FSB. i'll be upgrading soon...

 

[Crashman]

Your friend knows nothing about computers! 200 IS 100 and 266 IS 133! AMD uses a DDR bus, and your board uses DDR memory also. Now, DDR numbers are not actual frequencies, they are double the actual frequency. They represent the "Performance equivalent" of SDR frequency, because DDR sends two bits per clock cycle instead of one, for each data line. So he's wrong, DDR200 is ACTUALLY 100MHz, and DDR266 is ACTUALLY 133MHz. I believe the lie was created by AMD to eliminate "performance equivalent" explainations. In fact, the marketing of this lie was so successful that Intel was forced to follow suit with their so called "400" and "533" busses, which also run at 100 and 133MHz, but use Quad Data Rate.

So now that you know that 100MHz and 133MHz are real numbers representing the 200MHz and 266MHz ficticious numbers, you should be OK. But that still doesn't get to the heart of your problem, which could be:

1.) Your memory is overrated and should have been called PC2100 instead of PC2700. This happens more often than many people know. OR

2.) Your motherboard can't run it at the specified speed, OR

3.) Your motherboard can't supply enough voltage to the slots to meet the demands of the memory at the higher speed.

#3 is usually caused by an inadequate power supply.

You can try increasing stability of the RAM by increasing it's voltage in BIOS, if those settings are available.

<font color=blue>By now you're probably wishing you had asked more questions first!</font color=blue>