P4 Confusion on FSB and DDR-333

[Olias]

I?ve read through most of the post and couldn?t find a clear explanation on how ratios work. I?ll pose my question by using a scenario of what I would like to do.

- buy a 1.6A (Northwood)
- buy an Asus P4S533 (SiS 645DX chipset)
- existing Crucial PC-2100 DDR SDRAM

If I buy this CPU and motherboard and increase my FSB to 133MHz will this be similar to how the new P4-533?s run? Quad pumped, but no such thing as a real 2.13A? right?

What will I have to do to get my memory running at 266-DDR or maybe even 333-DDR?

If the CPU will run at 16 x 133FSB with a memory ratio of 1:1 (266-DDR) will the PCI and AGP be still running in spec?

Thanks for the help and sorry if this has already been posted and I missed it.

 

[Olias]

I think I found the answer to the first and second questions... 133 MHz (533 MHz) 1:1 266 MHz and if my Crutial can handle it 4:5 would give me 333MHz (DDR-2700)

4:5 meaning
4x33 for 133FSB (quad=533CPU)
5x33 for 166 Memory Speed (333-DDR)

What about PCI/AGP... will these ratios keep them in spec as long as I don't exceed 133MHz FSB?

 

[zxcv]

4:5 meaning CPU FSB to Mem ratio is 4:5. So for every MHz the CPU FSB runs at the Mem runs at 1.25 MHz. When you have the CPU at 133MHz the Mem will run at DDR333 [ (5/4)*CPU = 166 MHz which is DDR333]. Same kinda thing for the other ratios.

On the P4S533, after 132MHz the PCI divider is 1/4 meaning the PCI runs at one-quarter the speed of the CPU FSB. [ (1/4)*133 = 33.25MHz ]. Similary scenario with the AGP. Increasing your FSB will change these speeds. So you are correct that if you keep your FSB at 133MHz then your PCI/AGP will run as normal (for 100MHz FSB).

Just play around with this little tool from jcash at the Asusboards. Here

 

[oldfart]

Or, you can get an 845G based board and lock the PCI/AGP @ 33/66 and run any FSB you want and still be in spec!

 

[Olias]

OK, I couldn't resist. I ordered the 1.6A and a P4S533. I hope my Crucial PC-2100 will do 150MHz. I was planning on running 1:1 ratio at 150FSB. Wish me luck... I'll post my results here when I receive and install the hardware.

What should I ask for the following:
- EPOX 8KHA+,
- Tbird 1.4 MHz,
- Vantec 6035D HSF.

Thanks, Olias 😀

 

[Olias]

I got this combo togrther and WOW 2.4GHz at default 1.5v core with stock cooler... stable! I peeled the retail pad off before even using it. It cleaned up nice with brake cleaner and I applied standard white compound. 28C idle and 40C while looping 3DMark 2001se. My Crutial will also run at 150 or 166 without raising the RAM voltage. I did some test with my GF3-Ti200 and here are the results...

[Benchies]
3DMark 2001SE = 7300
RTCW Checkpoint = 114fps
Sandra CPU = 4381/2911
Sandra MEM = 2247/2257

Next step it to tweak the memory timing 😉

 

[Duvie]

my crucial ran 315mhz (126fsb) on my msi ultra ARU mobo...I hadn't even jacked voltages I think it could have done 333mhz ddr with conservative settings...The board only had a 4:5 ratio up to 132fsb...when I hit 133 and above which I did I reverted back to 1:1...

I then stepped up to asus p4s333 mobo bu I didn't take my pc2100 crucial with me...I stepped up to kingmax pc2700, and never tested it out anymore...

 

[CrazySaint]

Originally posted by: Duvie
my crucial ran 315mhz (126fsb) on my msi ultra ARU mobo

You mean 156, maybe? 😉

 

[Duvie]

No!!! In my thread I state I ran 4:5 ratio until 132fsb on my msi mobo...

So 126fsb was 126/4= 31.5 * 5 = 157.5 double pumped to 315mhz ddr.....

 

[Budman]

Somebody posted a little chart one time,I think it was Thugs.🙂

Here it is.

4:5 = +25%
3:4 = +33%
4:6 = +50%
3:5 = +66%
3:6 = +100%


DDR chart. . . . . .100fsb . . . 133fsb . . . 150fsb . . . 166fsb
4:5 = +25% . . . 250ddr . . . 333ddr . . . 375ddr . . . 415ddr
3:4 = +33% . . . 266ddr . . . 354ddr . . . 399ddr . . . 442ddr
4:6 = +50% . . . 300ddr . . . 399ddr . . . 450ddr
3:5 = +66% . . . 332ddr . . . 442ddr
3:6 = +100%. . . 400ddr

 

[oldfart]

Nice work on that chart!

I added in 160 FSB

4:5 = +25%
3:4 = +33%
4:6 = +50%
3:5 = +66%
3:6 = +100%


DDR chart. . . . . .100fsb . . . 133fsb . . . 150fsb . . . 160 fsb . . . 166fsb
4:5 = +25% . . . 250ddr . . . 333ddr . . . 375ddr . . . 400ddr . . . 415ddr
3:4 = +33% . . . 266ddr . . . 354ddr . . . 399ddr . . . 426ddr . . . 442ddr
4:6 = +50% . . . 300ddr . . . 399ddr . . . 450ddr
3:5 = +66% . . . 332ddr . . . 442ddr
3:6 = +100%. . . 400ddr