Does PC133 memory actually run 133 Mhz in 100Mhz FSB ?

[Qzruh]

My colleague said that the memory clock should be the same as the FSB, since it is a Syncronous DRAM, so that the PC133 memory paired with processor which have 100 Mhz FSB, only run at 100 Mhz.

I dont think this way, but i am lack of knowledge of this, i have read (sometimes ago, i forgot) in anandtech or tomshardware, they said that the PC133 run in 133 Mhz in the motherboard that have the chipset supporting 133 Mhz memory clock. So i think the chipset is envolved in this case..

Anyone can explain me ? pleasee.....

 

[ShVen]

RAM is fsb backwards "compatible" meaning, you set yer fsb to 100, yer cpu and ram will run at 100mhz fsb... ok?? also if you can overclock ram, why shouldnt you be able to UNDERclock it too?? think about it, hehehe

basicly: yer ram runs at what you tell it to, if it dont like it, it wont work, if it does then everything is ok!!

 

[Qzruh]

Thx for your post, sorry but this does not answer my question

I will give an example, i have a T-Bird 700 which have 100Mhz FSB, with PC133 memory. Some people telling me that my PC133 memory will not run in 133Mhz frequency, since my processor FSB is only 100 Mhz. I dont think this statement is correct, because i know that my chipset, VIA, is supporting 133Mhz memory clock. So i ask anyone *please* who can explain me technically what is the relationship between FSB clock ,memory clock, and this VIA133 chipset, how come the 100Mhz FSB can accept the data from an SDRAM with 133Mhz memory clock, since the memory is syncronous.

Thanks again...

Andy

 

[conlan]

whatever speed (mhz) you set your FSB setting in your bios be it 66 , 100 , 133 or anywhere else , that is the speed at which your memory is running.

 

[shiznut123]

The via chipset allows you to add the FSB with the pci clock(1/3 of FSB) so if you have 100mhz FSB then you can add 33mhz because of the 33mhz pci bus.

 

[ShVen]

there are motherboards that support different cpu and mem clockspeeds, but i doubt you have one of those... and if that is the case:

FSB = CPU/MEM-Clock

 

[SEOTAIJI]

lets say you run your comp at 7.0 x 100fsb (700mhz).. then your ram will be running at 100mhz
but if you set 7 x 133fsb (933mhz).. then your ram will be running at 133mhz
pc133 ram is backwards compatible with lower fsb computers
there is also options that sets ram speeds at a certain ratio to the fsb speed..

oh.. i get your question
well.. if your cpu can handle 7x133, then youll have a nice cpu that overclocks well
but youll probly have to lower your multiplier and increase fsb to squeeze every juice from your cpu (if its amd)
also ram
if you get pc100 ram.. it might go to like 115mhz if your lucky
and if you get pc133.. it might go 150mhz if your lucky..
then there is high quality ram which goes to like 166mhz.. and stuff

i think the difference between the kt133 and kt133a motherboards is that the regular kt133 motherboards werent made to handle fsb speeds that were over 100, while the kt133a motherboards were built to run at higher fsb speeds like 133 or even more, but in both cases, they overclock to a point over thier limit like maybe a kt133 motherboard will go to 112, while the kt133a will go to 145.. stuff like that
kt133a motherboards like asus a7v133~!! are good motherboards(better for overclocking in my opinion).. i can go to 142fsb and have my comp pretty stable
i hope this answered a question or two that you might have had
ok bye

 

[lundog22]

I had an A7V (VIA KT133), it can do 100FSB+ w/ RAM set @ 133Mhz. Got the new A7V133 (VIA KT133a), it can do 133FSB w/ 100 or 133MHz RAM or higher.

KT133a support 133FSB, while KT133 support 100FSB.

 

[btac]

What I think you are asking, Qzruh, is does your particular 133mhz memory run at 133mhz or is it limited by the Via KT133 chipset. Anandtech has tested many KT133 chipset boards and found that about the best the KT133 can do on a FSB is about 110mhz. You don't say what board you have - they are all a little bit different but the KT133 chipset boards all have the common denominator of around 110mhz limit. So your PC133 will run that fast, at least. If you get a board with a KT133A chipset, then you can run your PC133 memory at 133mhz (or higher).

 

[Qzruh]

Thx for your post....

My board is ABIT KT7, with dram speed = sysclk+pciclk, and i'm using PC133 memory. FSB = 100Mhz, multiplier = 7

With that configuration above, my memory should run 133 Mhz right ? but some people told me that memory clock is dependent on the FSB, so, if my athlon is set to 100 Mhz FSB, my PC 133 is useless, because the memory will only run 100 Mhz since my athlon FSB is set to 100 Mhz

is this right ?

 

[lundog22]

Double check your BIOS, there should be an option to run your RAM @ 133Mhz. Default should be 100Mhz in many KT133, like yours.

 

[Qzruh]

Hm... maybe my question is not clear enough... i'm sorry about my english

I dont have any problem with my memory or board installation, i just ask, is it true that the memory clock is dependant with the FSB clock, and always the same with the FSB clock ? although i have set the memory clock @ 133 Mhz ?

Some people said that IF i have processor running 100Mhz FSB, then my memory clock WILL ALWAYS run @ 100 Mhz, although i set the memory to run @133

is that correct ? or not ?

Thx again...
Doh... my poor english

 

[Technonut]

If you have your FSB set at 100, and the RAM set at Host CLK + PCI CLK in the KT7's SoftMenu, your RAM will be running at 133MHz.

If you have good quality RAM that will handle more than 133MHz, you would get better overall memory and system performance by using a combination multiplier/FSB overclock.

For example, if you have your FSB set at 107/35 + 3 (110), and your RAM at Host CLK + PCI CLK, your RAM would be running at 145MHz. ( Host CLK FSB 110 + 35 PCI CLK = 145MHz RAM speed.

 

[Innoka]

Didn't read all the above posts but there are chipsets for Intel which allow you to set the fsb and memory bus separately. My motherboard can do this.
You can recover 40% of the performance difference between running your processor at the lower bus compared to the higher one by just choosing the faster memory bus.
Look at Anand's article "overclocking the celeron".