HELP!!! i845E mobos and memory compatibilities/limitations question

[Sunny129]

i'm in the market for a mew mobo. i have had my eye on the SiS 648 chipset b/c i'm particaularly interested in the features it offers: MultiTOIL (1GB/s interconnect bandwidth between the north and south bridges), serial ATA, IEEE1394, and some other features that haven't been ordinarily included in P4 chipsets thus far. the only problem is that no mobo maufacturers have been taking advantage of all these SiS 648 integrated features, and are therefore leaving features out on their mobos. if only i could find a SiS 648 board with all the features i desire, and an AGP/PCI bus lock, then i would be ordering the board right now. unfortunately, no such combination of features exist on any one SiS 648 board, so i'm still waiting for one. but the wait has been long, and my patience is slowly wearing thin. so my next chipset option would be the i845E b/c i'm trying to stick to a DDR solution. anyways, the ASUS P4B533-E uses an AGP/PCI bus lock (i really need one of those), and although it doesn't support IEEE1394 or serial ATA, and only has half the interconnect bandwidth that the SiS 648 has, i'm growing tired of waiting for a SiS 648 board containing all the features i want. now i'm not saying that i've given up on the SiS 648...i still plan on holding out a bit longer to see if any other board makers put out something i like. but in the mean time i would just like some i845E memory questions answered. now official specs say that the chipset handles PC1600 (DDR200) and PC2100 (DDR266), but none higher. however, i've looked at some forum members' rigs, and some are using PC2700. i havent come across anyone with an i845E board using PC3200 yet, but as long as the CPU : DRAM clock ratio is set corectly, even PC3200 (DDR400) memory could function correctly on an i845E board, correct? for example, at a 400MHz fsb, the ratio would be set to 1:1 if you want the PC3200 to run @ 400MHz, or if using a 533MHz fsb, and you want the mem to run @ 400MHz, the ratio would be 4:3. or am i way off? i'm just trying to figure out the fsb/mem ratios and how they work, and also what kind of memory i could use on an i845E boardeven though it only officially supports up to DDR266 speeds.

 

[jaeger66]

The P4B533-E has Firewire. A 1:1 ratio on a 400(100 x 4) fsb is 200, and 266 on a 533(133 x 4) fsb. Only a few 845E boards allow asynchronous memory, the Asus is one of them. So, a 133 fsb and a 3:4 ratio gives you a memory speed of 355. 133 x (4/3) = 177(354 DDR).

 

[LivinLaVivaPollo]

Just a couple of things:

You'll find that the interconnect between the nb and sb on SIs 648 boards offers no real world performance advantage. I believe the Abit sis 648 does indeed have an agp/pci lock, but it doesn't overclock passed 143 FSB at least from initial reviews. The Abit IT7Max2 supports serial ata and is an 845E board, if you are in the market for one. It comes with the typical Abit MAX series pro's/con's such as firewire, usb2, spdif out, but no serial com ports, parallel ports, or ps2 ports.

I'm actually going to purchase the IT7 myself, because of the fact that it can run a gig of memory at DDR400, a feat quite difficult to accomplish on any board.

 

[Sunny129]

oh yeah, hence the term "DDR." so if if my fsb is at 533MHz (4x133) and my CPU : DRAM ratio is at 4:5, then my meory is at 166MHz (which is effectively 333MHz if DDR memory is used)? hopefully i have my numbers straight now. someone tell if if that sounds right...

as for the ABit SiS 648 board (SR7-8X), it seems to be the only SiS 648 board currently on the market that has an AGP/PCI bus lock. unfortunately this board's performance is less than par (as reviewed by HardOCP and AnandTech), and is certainly out of the question for OCers. i will not be getting this board. its like i said, if it isn't one thing, its another...all the features and no AGP/PCI bus lock, or an AGP/PCI bus lock and few features, or AGP/PCI bus lock but performs poorly...i can't win. anyways, i also have my eye on the P4B533-E since i just found out it has firewire support...i wish it had SATA, but oh well. i've learned that i'm not going to get 100% of what i want in a board, but i'm still waiting to see...

 

[jaeger66]

Originally posted by: Sunny129
oh yeah, hence the term "DDR." so if if my fsb is at 533MHz (4x133) and my CPU : DRAM ratio is at 4:5, then my meory is at 166MHz (which is effectively 333MHz if DDR memory is used)? hopefully i have my numbers straight now. someone tell if if that sounds right...

Yes, that's right. However, only 845G boards support the 4:5. Of course, there's still some debate about how well, the 845G chipset's memory controller seems to get flaky if you go over 266. I'd stick with an 845E and go for the 3:4.

 

[Sunny129]

ok, so now i know the only the i845G has the 4:5 ratio, and the i845E only has the 3:4. but i thought the only difference between the chipsets was onboard graphics. do they also use different memory controllers? and how am i supposed to know which ratios are supported by which mobos? is it all a matter of which memory controller they use?

 

[klc314]

Actually, the P4B533-E can be tricked into running the memory at 354, by setting the DDr voltage to 2.9V (for stability), rebooting, setting the sixth dipswitch to 1, and then rebooting. You should have the CPU running at 133, and the memory running at 177 (133 X 4=DDR354).

 

[Sunny129]

well that's an interesting trick...i'll keep that in mind if i get the board...

 

[jaeger66]

Originally posted by: Sunny129
ok, so now i know the only the i845G has the 4:5 ratio, and the i845E only has the 3:4. but i thought the only difference between the chipsets was onboard graphics. do they also use different memory controllers? and how am i supposed to know which ratios are supported by which mobos? is it all a matter of which memory controller they use?

Only a handful of 845Es support the 3:4. Most just give 1:1. The Asus, Abit, and I think the Epox 845E boards are the ones that have 3:4. And yes the 845E and 845G use different memory controllers.

 

[CBone]

AFAIK, the Asus 648 board still doesn't have PCI/AGP lock. At least not enabled in the current BIOS. I just got the Albatron PX845E Pro 2 last week and I have my 1.6@2.38 for now with mem benches of ~3K. It's running like a champ. Not like my stupid 4G4A+. That piece of garbage. I could only get the same chip/ram up to 1900 with OMG,-when-is-this-POS-going-to-crash-next,-I'd better-cross-my-toes-too stability. So far, this Albatron board is rocking the casbah.

CBone

 

[Sunny129]

i'm just hoping that their next bios revision includes an AGP/PCI bus lock, b/c the P4S8X is the SiS 648 board i'm most interested in...