Q on using PC133 mem, how is yours set up?

[JoeJerky]

In my current system I have one stick of 128mb PC100 and one stick of 128mb PC133 which I am running a celeron with a FSB setting of 75mhz. I now have a Abit KT7 (waiting on a Duron 600 to be shipped) that I am trying to decide if I should run the mem (FSB) at 100mhz or 133mhz... At 133mhz means that I need to buy another stick (eventually).

As far as the setup though, I notice in the Abit manual there is several setting for the FSB/PCI clock. There is the "normal" 100/33 setting but for the 133mhz FSB the corresponding PCI setting is 44mhz. This seems quit high since the nominal setting for the PCI is 33mhz. Now... The next higher BIOS setting possible is 136/34, the next lower setting possible is 127/42.

I assume that the higher one would be the best setting to use??? I was also wondering what others are using in their set ups? I appreciate the info. Thanks!!! :Q


The Jerk...

 

[paulip88]

That is probably a typo or something.

The way the mem bus works on that chipset is FSB speed or FSB+PCI clock. The default PC133 setting is 100FSB and 33PCI, doing the FSB+PCI clock.

I suppose, however, that you can get the 44 PCI by doing a 133FSB, without adding the PCI clock. This is pretty much impossible to do with the KT133 chipset. Don't worry about it.

Most people are doing the OCing by upping the multiplier and keeping the FSB at 100. Those with PC100 use the 100MHz clock, those with PC133 use the 100FSB+33PCI setting.

There are also some people who up the FSB too, but those people are getting FSBs up to around 110, not much more.

 

[JoeJerky]

Hmmmm. I guess I don't understand fully.

I was under the impression that PC100 memory was needed to run on a 100mhz FSB and that PC133 memory was needed to run on a 133mhz FSB. I take it that a Duron or a T-Bird CPU (normally) needs a 100mhz FSB setting. I thought that it could use either 100mhz or 133mhz. Is there any CPUs that run on a 133mhz FSB?

It looks like I had a brain fart. I thought that, gee, I have PC133 memory; I just set the FSB to 133mhz and adjust the multiplier accordingly, and away we rock. But now that I think about it a little more, that is wrong. I guess.

The manual for my Abit KT7 lists "FSB/PCA Clock" as the item in the BIOS that is adjustable. I will just set it at 100/33. This setting should be ok with my PC100 and PC133 memory. I think. I will do more scouring on the net for info. Thanks for bringing it to my attention.

If anyone else has anything to add, I would appreciate the info. Thanks!!!


The Jerk...

 

[dude]

PC100 memory are spec'ed up to 100mhz. PC 133 memory are spec'ed up to 133mhz. PC66 memory are spec'ed up to 66mhz. Of course, some can go higher if you push it there.

But, of course, PC 100 memory CAN do 66mhz and 100. PC 133 mem can do 133, 100, and 66, or anywhere in between. PC 150 memory can do 150, 133, 100, 66. It's perfectly fine.

this reminds me of an article from Mr Guru.

 

[JoeJerky]

That was my understanding, Dude...

I was confused, but now my brother, I see the light... Heh heh heh

I am finding out that it depends on the proc and mobo you are using, which I didn't realize fully. I was under the impression that the Duron/T-bird could use a 133mhz FSB, in fact, it uses the 100mhz FSB max(non-o/c'd)... So I guess my memory will suffice... Thanks for the input though!

The Jerk...

 

[kylebisme]

naw, you dont have it quite right yet. the t-birds and durons run on a fsb of 100mhz ddr, so efectivly 200mhz. the memory can be set at 100mhz for pc100 and 133mhz for pc133. 133mhz is acomplished by running the memory at the speed of the hostclock (fsb of 100mhz) + pci clock (1/3fsb). so, when you up the fsb to 110 with host+pci you get 110 + 1/3(110)~147mhz on the memory. hopfuly this helps you understand how your new system will work.

honostly, im not sure what you use your computer for, but i would rather have the memory at 133 with 128mb than 100 with 256, however if your a big multitasker you may find diffrent. however i would try to run the pc100 at 133, you never know what it can do untell you try. i have a dimm that was purchaced as generic pc100 cas3 and has run great at cas2 up to 144mhz so far, i have yet to have the components to push this little stick to its max.

anyway, explore your options and try it all, you have a great little setup on the way just wating to be tweaked to the limit

 

[Sedul]

Snowman,
i dont get ur'e descrtipnoa botu
host + pci clock on memory thing

so i u're fsb is 100mhz. and u're pci clock is set at 1/3 (33 mhz)
that means u're memeory runs at fsb +pci = 133

Ins't hte memory the same speed as the fsb? and the pci just uses a multiplier on the fsb. and runs slower

so isn't it possilb eot set u're fsb at 133mhz with a pc133 piece of ram.. and set the pci clock to like 1/4 so the pci bus runs tat 33mhz and nothing gets screwed . but u get the advnateges of ram runnin' at 133 mhz. more bandwidth!! 1.06 gig / sec or osmething.

Joe Jerky i woudl run my ram at 136/34 ..hehe. and then just play around with the multiplier
but hte thing is. i don't think the kt7 can take it. cause of that double data architecture athlons have..
sumpin' like dat.

 

[JoeJerky]

Hey Guys... Thanks again for all the info.

As I dug a little deeper into the mobo manual I found a setting: "DRAM Clock". This is the description: "Two options available: Host CLK > HCLK + PCICLK. The default setting is Host CLK. This option is used to set the working speed of the SDRAM. It is the same as the CPU working frequency, plus or minus PCI clock. A SDRAM working speed of over 133mhz will stay at 133mhz."

So if I am getting this... In a ?normal? set up I would set the "CPU FSB/PCI CLK" setting to 100/33. If the DRAM clk setting is at Host clk, I would have my mem running at 100mhz. If I set the DRAM clk setting to HCLK+PCICLK, I would have mem running at 133mhz.

My current mobo is a Asus TX97-LE, which doesn't have these fancy settings, that is why I am unfamiliar wit dem...

Now, there is another setting after the DRAM Clock. It is "Auto Detect DIMM/PCI Clock". The possible settings are: "Disable > Enable", I assume that I would set this to Disable if I were tweaking the mem bus?

Thanks for all the help!

The Jerk...

 

[kylebisme]

what the auto detect feture does is read the information off the dimm, so your pc133 will auto detect at 133 but the pc100 will auto detect to 100. so if you put both in with "auto detect" youl get 100mhz memory speed. what i did with my pc100 was dissable auto detect and pushed ther bios to hostckl+pci clock for 133mhz, your pc100 might do the same. if not just run your 256mb at 100 and the try the 128mb at 133, seee how it prefoprms, then deside what to use in the long run. play with the cas2/cas3 settings and see what happens too.