bus speeds and RAM??? 1

[Daire]

hi, i am building a system with a mobo FSB speed of 333 and and Athlon 2800 also 333, can I use my old 266 DDR on the new board and can i mix it with new 333Mhz RAM?
Will 400Mhz DDR run at 333 cause thats the FSB speed of the motherboard?

 

[micker377]

You need PC2700 (333). Without making changes, it won't even boot on PC2100 (266). PC3200 (400) will run at 333, but you are wasting money.

 

[Lemon13]

can I use my old 266 DDR" give it a try, mostly they run but...
"can i mix it with new 333Mhz RAM" is not recommended at 333mhz fsb (timings of the 266)
"Will 400Mhz DDR run at 333" yes, without any probs.

 

[Daire]

Thanks, the motherboard says it has a max speed of 333 but supports RAM of pc2100,2700 and 3200 so it looks like it will take 266Mhz RAm but will this reduce the mobo and cpu fsb to 266 also - will jumpers have to be changed?

What about Dual Channel, does this require special ram?

 

[paparazi]

If you choose to use your old stick of PC2100 (266) mixed with either a stick of PC2700 or PC3200 (333/400) the most likely outcome is that the PC will only boot at the slowest memory speed which is 266, what this means is your new processors front side bus will be running at 266 and not 333, effectively "underclocking" the CPU.
So instead of correct actual speed showing 2.08ghz it will be running slower around 1.66ghz
Ditch the PC2100 (266) sell it on, and go for either PC2700 or PC3200 (if there isn't much price differance go with the PC3200) make sure it's branded, crucial, Kingston, Corsair etc the faster memory will just run at the slower speed for now but gives you more possibilities in the future.
Martin

Replying helps further our knowledge, without comment leaves us wondering.

 

[Daire]

Thanks Paparazi, was afraid of that
I currently have an Athlon 2400 but have the oppertunity to sell it and thought i could go to 2800 cheaply but sounds like i would be taking a step down if you say the new cpu will run at approx 1.6ghz

Dont really know what to do as I cant afford the faster RAM just now

 

[paparazi]

Hi Daire,
It probably wouldn't feel much slower than the XP2.4+, even at the slower 1.66 speed the XP2.8+ has twice the level 2 cache which would go part way to bridging the gap (remember the XP2.5+ only runs at just over 1.8ghz but is quicker than the XP2.4+ running at 2gig)
Running the setup like this wouldn't damage anything and you could get the faster ram at a later date?
Just a thought.
Martin


Replying helps further our knowledge, without comment leaves us wondering.

 

[Daire]

Thanks again, think thats exactly what i will do.

just spent past two hours reading all the posts on FSB, DDR , dual DDR, ratios, motherboards, new builds - lot of interesting stuff out there.

Cheers

 

[cdogg]

I just wanted to point out that since the early Athlons started using DDR, the "memory bus" often had the ability to run asynchronous to the "frontside bus" of the CPU. In other words, you could have your CPU running on its 333MHz FSB while using memory running at 266MHz. Perhaps you are using a mobo that only uses synchronous settings, in which case paparazi would be correct. However, most allow for asynchronous settings to allow slower or faster memory speeds without affecting the FSB.

With that said, it is not recommended that you ever go this route even though it's possible. Running the two busses out of sync causes one to lose time to latency (waiting for the other to execute when the load gets intense). Therefore, you always want to shoot for a perfect match in speed, making paparazi's suggestion ultimately correct.


~cdogg
[tab]"All paid jobs absorb and degrade the mind"
[tab][tab]- Aristotle
[navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884

 

[Daire]

Hi, just to let you know how I got on.
Replaced old Athlon 2400 and Matsonic MS8157E mobo 266Mhz 4xAGPwith
New Athlon 2800 333Mhz
New MSI KT4AV-L 333Mhz FSB 8xAGP
Creative Labs Blaster 128MB 8xAGP DX9 graphics
2 x 256MB PC2100 266Mhz

BIOS detected Ram FSB as 100Mhz and CPU as 100Mhz
This gave me a rating of 1.25Ghz and a 3DMark01 SE of 4580
SiSoft Sandra CPU Arithmetic Benchmark of dyrystone ALU 4719 MIPS
Whetstone FPU of 1950

Set the Ram to 133Mhz and CPU to 166Mhz
This gave me a rating of 2.09Ghz(correct) and a 3DMark of 5104(very low)
SiSoft Sandra CPU Arithmetic Benchmark of dyrystone ALU 7972 MIPS
Whetstone FPU of 3287
CPU temp 42C

ALSO – Sandra says the AGP bus is not being used but I changed PCI to AGP
In the BIOS, the AGP speed is set to AUTO and wont let me change it to 8x

Don’t know whether to replace the 266Mhz RAM with 333????
Why does Sandra say AGP not being used????
I thought my old 3DMark score of 5200 would nearly double going from 4x to 8xAGP????

Any Ideas

Thanks

 

[paparazi]

Daire
Going from 4X to 8X AGP has a minimal effect especially on lower end graphics cards, an 8X MX440 GF4 for instance performs less than 2% better than a 4X MX440.
It is a common misconception but making the road twice as wide doesn't make the car go any faster, with a fairly entry level card (FX5200, Radeon 9200) a 4X bus can handle the video data with ease and still have capacity for more video data.
It's only with the very fastest of GPU's that a 4X AGP bus offers any bottleneck and then only slight, with cards like the Geforce FX 5950 and ATI's Radeon 9800XT which render masses of information the 8X bus just starts to tell.
Martin


Replying helps further our knowledge, without comment leaves us wondering.

 

[cdogg]

Yes, that is a common misconception about AGP. The 4X and 8X rating is bandwidth, not speed. It is like widening a highway without increasing the speed limit. So unless you have a lot of traffic (which some intense games may give), the "widening" may only help some of the time. Remember, AGP is the connection between the card and the rest of the chipset on the motherboard. Since most processing from a game is done on the card itself, the AGP bus plays less of a role when compared to the GPU and internal clock speed of the video card.

It might be a couple years before we see the real benefits of AGP 8X as cards get faster and the games get more floating-point intensive requiring more of the CPU.


~cdogg
[tab]"All paid jobs absorb and degrade the mind"
[tab][tab]- Aristotle
[navy]For general rules and guidelines to get better answers, click here:[/navy] faq219-2884