AMD Athlon Bus Speed Question ^^

[Guest]

OK..
someone asked me..

if my bus is at 100 or... 200 ( ev6 )

How can pc -133 run at that
doesnt the memory have to be running at the same speed as the bus?

How does that work..
I have pc -133 and someone... told me its useless and i should of for pc -100 becuase the bus is 100MHz..

But i think they run at different speeds correct?

explain pls

-- They have found a way to harness the power of a thunderstorm and expell it with great force!--

 

[Raystonn]

For someone labeled an "addict" by the forum I'm surprised you don't already know this. Anyway...

If you run a 100MHz bus, you should use PC100 ram. If you run a 133MHz bus, you should use PC133 ram. If you are running PC133 ram on a 100MHz bus it's being underclocked and used as PC100 ram.

If you run a 100MHz bus with DDR (effectively 200MHz) you should use PC1600 ram. If you run a 133MHz bus with DDR (effectively 266MHz) you should use PC2100 ram. If you are running PC2100 ram on a 100MHz bus with DDR, it's being underclocked and used as PC1600 ram.

-Raystonn

-- The center of your digital world --

 

[Guest]

I told him that. Damn kid wount listen to me. Hes like "but my memory is 133 so it has to be 266 cause i have double data path way. Im like no it isnt you only have sdram not ddr, but hes thick.

SPUDMUFFIN

<font color=blue>Just some advice from your friendly neighborhood blue man </font color=blue>

 

[Guest]

I never said my memory was double pumped

i said..
the bus speed is

Then why the hell does my motherboard
Gigabyte 7ZM
support KT133 Chipset and ........
it says supports pc-100 and ....... AND PC 133

and its only for SDram
Why then?
ALSO>>
IN cmos im running a Duron 800 100MHz bus ( 200 EV6 )
and..
in benchmarks
the mem running at 133 is way higher then...
the mem set to 100

why?

-- They have found a way to harness the power of a thunderstorm and expell it with great force!--

 

[Raystonn]

You can select your frontside bus speed (FSB) in BIOS. If you want to actually use your PC133 memory, set it to 133MHz.

-Raystonn

-- The center of your digital world --

 

[Guest]

But his durons a 100 fsb. So there will only be trouble.

SPUDMUFFIN

<font color=blue>Just some advice from your friendly neighborhood blue man </font color=blue>

 

[Raystonn]

I don't know a great deal about the Duron, but are you saying AMD locked the frontside-bus speed that the chip will accept? The Duron can't handle a 133MHz frontside-bus? Looks like he wasted his money.

-Raystonn


-- The center of your digital world --

 

[Guest]

my cpu is at 100 or ( 200 ev6 )

my memory is set in cmos to..
133

it runs and scores way higher memory benchmarks then with the mem set at 100

how does this work

are u saying if my bus is set at 100, my memory it at pc-100 speeds?

-- They have found a way to harness the power of a thunderstorm and expell it with great force!--

 

[Guest]

Ya ya i told him that too. But hey its the cost\performance ratio right? Thats what its all about.

SPUDMUFFIN

<font color=blue>Just some advice from your friendly neighborhood blue man </font color=blue>

 

[Raystonn]

"my cpu is at 100 or ( 200 ev6 )

my memory is set in cmos to..
133"

I don't understand what you're talking about here. There is only one bus that's related to the CPU. That's the frontside bus. This is the bus that's used to communicate between the CPU and memory. From where are you getting these 2 differing numbers? If you have SDR (non-DDR) SDRAM, then your frontside bus is running at either 100MHz or 133MHz. Pick one.

-Raystonn

-- The center of your digital world --

 

[Guest]

I know hes crazy. I spent one night argueing over it till i just got mad and logged off ICQ.

SPUDMUFFIN

<font color=blue>Just some advice from your friendly neighborhood blue man </font color=blue>

 

[Guest]

What im saying is
i have NO NO NO NO settings in cmos for the FSB none!

On the board its set to 100...

now.....................
in CMOS i have.. a setting for the memory
100 Cas 2 or.. 133MHz cas 3..
its set at 133MHz with the bus speed at 100

it performs faster in sisoft sandra at 133 then it does at 100
with the bus always at 100...

How is this possible?


-- They have found a way to harness the power of a thunderstorm and expell it with great force!--

 

[Guest]

Also
this board handles 133 FSB
but max i can get stable is 118

...


-- They have found a way to harness the power of a thunderstorm and expell it with great force!--

 

[Raystonn]

"i have NO NO NO NO settings in cmos for the FSB none!"
"its set at 133MHz with the bus speed at 100"

Not only do those two statements conflict, but you conflict yourself in the second statement alone. The FSB is the 'bus speed' that you're discussing. So you obviously have a setting for it. Now as far as the second statement goes, which one is it? 133MHz or 100MHz? It can't be set at both.

-Raystonn

-- The center of your digital world --

 

[Guest]

The Via chipsets can run the memory asynchronous to the fsb.

This has existed as far back as the kx133 chipset.

What this means is your fsb will run at 100 (100x2 with Ev6)
and the chipset will run the memory at 100+33 or 133 mhz.

You are not wasting your pc133 on any modern chipset.

The intel people should do a little more research as even the Via chipsets for intel processors can run the memory asynchronus to the bus clock.

 

[Raystonn]

You're still wasting money. Your processor is not able to use your PC133 memory at a rate any higher than 100MHz.

-Raystonn

-- The center of your digital world --

 

[Guest]

I believe what KILRSAT says

i know my memory is running at pc-133 and the bus at
100(100x2)

i know my memory is running at 133


-- They have found a way to harness the power of a thunderstorm and expell it with great force!--

 

[Raystonn]

Your memory may be running at 133MHz when accessed through DMA by the chipset and expansion cards, but it's being accessed through the frontside bus by the CPU directly; and that is at 100MHz.

-Raystonn

-- The center of your digital world --

 

[Guest]

I am running a Duron 700 @ 900 with VIA 133 chipset and the facts do not support your contention.

1. The Duron has a double pumped 100 Mhz bus effectively allowing 2 transfers per clock between the processor and North Bridge.

2. The North bridge "buffers" asynchronous memory transfers between SDRAM and processor.

3. Running asynchronously IS less ideal than running with the same clock (which happens automatically when a 133A chipset is used with a 'C' athlon on 133 SDRAM) but still better than running 133 SDRAM at 100 on a VIA 133.

4. Hint .. also really good idea to set 4 way interleave on the SDRAM for a free performance boost (if your BIOS allows)

If you don't want to accept my word (and I have run the tests) go to Aces where the real experts are!.

I am running an Epox 8KTA-2 mobo (there is not a wide choice in South Africa) and I cannot get processor FSB above 112 (224 double pumped) but this is reported to be a known VIA 133 story (fixed by VIA 133A). My memory (crucial 133 Cas 3)
is then running at 148 Mhz.

 

[funkdog]

Man what a confusing thread. Does this guy know what in the world he's saying??

 

[Guest]

<b>Raystonn</b>, that is incorrect:
>>>Your memory may be running at 133MHz when accessed through DMA by the chipset and expansion cards, but it's being accessed through the frontside bus by the CPU directly; and that is at 100MHz.<<<<<

The memory bus does NOT spontaneously change its speed. It runs at the same speed, connected to the northbridge, all the time.

<b>tbirdinside</b>, This is how it works:
For both the Athlon, and Duron (all versions) the cpu to northbridge (FSB, ev6 bus) runs at either 100MHz DDR or 133MHz DDR (effectively 200MHz/266MHz). Normally, the memory (northbridge to memory) bus runs synchronously to the FSB, but with the Via SDR chipsets, the memory bus can be clocked at FSB + 33MHz when the FSB is clocked ~100MHz. This is the same for the Via P3 chipset, by the way.

There are some slight downfalls for running the memory asynchrounously to the FSB, but for SDR SDRAM it is possible. This is why the DDR chipsets will ONLY run the memory at 100MHz DDR when the FSB is set to 100MHz DDR (Athlon-B/Duron).

Since the northbridge to cpu bus is runs DDR, the increased bandwidth of the asynchronous memory bus can be utilized, which is not entirely true for the P3. This is why your memory benchmarks score higher when the memory is clocked at 133MHz instead of 100MHz. For maximum performance, you would also want the most aggressive memory timings that your RAM can handle.

Let it also be known that the FSB limitations of the AMD chips was attributed to the KX133 or KT133 chipset (which failed at ~118MHz DDR). For the chipsets verified for 133MHz operation (KT133A, AMD760, AliMagic...) both Athlon-B's and Durons will gladly run at a FSB of 133MHz, so long as they can handle the final clock speed. Just look around this forum. There are more than a few users doing this.


I hope this clears up some misunderstandings anyone may have had.

--------
I have not yet begun to procrastinate.

 

[Tom_Smart]

i have the same mobo, i use pc133, whith the fsb set to 112 using the dip switches on the mobo. the memory is reported in sandra professional2001e as being 149MHz. i assume this is hostclk +33 (i think this is how it manages to run the ram at 133) the total should be 145 i am assuming the extra 4MHz is some sort of a %error by sandra or the mobo. am i mistaken or on the right tracks. and if your fsb is at 118 whats with the 133 report by sandra all about?

every thing is personal when your a person

 

[Tom_Smart]

"a known VIA 133 story" i have the same chipset and can' get the fsb over 112 using the dip switches on mobo, however i can get it to 118 if i use a software utility such as CPUCOOL this lets me change the fsb from within winnows. i know i can go higher but it is unstable as i am only using a standard cheapo fan. my brother with the same set up (ga7zm pc133 athlon 1GHz) is using a much better fan and gets his all the way up to 124 although a little unstable after 8-9 hours. the setting do work as sandra reports improved benchmarks.

every thing is personal when your a person

 

[Guest]

Bartleby saying the same thing

 

[priit]

Bartleby is correct, the trick with VIA KT133 chipset and PC-133 RAM is just running memory async. That's really old technology, even VIA's old MVP3 SS7 chipset was capable of doing that (running memory and FSB asynchronously). I guess just Intel hasn't invented it yet BTW, specially Durons are pretty sensitive about system's memory bandwidth (cause of small L2 cache), using PC-133 memory instead of PC-100 may boos performance in some apps (quake3) up to 15-20%.