ASUS P2B memory issue

[Gepl]

Last week I've successfully replaced my old Celeron 300A@450 for P3 1 GHz processor. The system is rock stable, but there is a memory issue that I wasn't aware of until recently. If there's Micron PC133 SDRAM in all three DIMM slots, MemTest-86 finds errors around 310 MB. I've tried to compress a large file with WinRAR and the unpack fails every time... BUT, if I remove one or two dimms, the memory error is gone.

I have to point out that these three 128 MB Micron dimms are 100% error free. They operate at CAS2 at 133 MHz without a problem, even though they're specified as CAS3 (7,5 ns press). So, is this a known problem with ASUS P2B boards (revision 1.10)? Would the system work ok if I put in two 256 MB dimms?

 

[rimshaker]

Hmmm. Interesting problem. I upgraded my old P2B system to a P3-850 a few months ago. I've never used all 3 dimm slots so i never ran into that problem, I only have 256MB installed. Is this system overclocked? The only other problem i've heard with the P2B is the support for the highest P3-1.1GHz cpu. With the current beta bios, 1GHz is the highest that can be reached.

 

[Gepl]

I set 1,75 V for P3 on MS-6905 Master CPU Converter Board and 7,5 x 133 MHz on Asus board. BIOS is the current 1014 beta1. There's no difference if I adjust the memory timings in bios, except that memory bandwidth changes. I've also set the VIO jumper to Test mode with no luck. Error appears only if all three dimms are full.

 

[rimshaker]

It's gotta be a memory timing issue. The P2B boards with the BX chipset weren't really designed to handle 133fsb speeds. This is a similar problem found in the new nForce chipsets having memory problems with 3 memory slots all filled. Try lowering down to PC100 to see what happens.

 

[Gepl]

You got the point, I guess. I didn't experience any memory problems when Celeron was running at 4,5 x 100 MHz, so that should be it.

I'm not willing to lower fsb, because everything else works perfectly ok + the P3 is actually designed to operate at 133 MHz fsb... I'll try to exchange these Micron sticks for 2x256 MB CAS2 SDRAM.

Thanks for your input!

 

[mbf]

Gepl, you should consider the fact, that you're also overclocking pretty much everything else in your system if you continue to run the FSB at 133MHz. The 440BX chipset was designed to run at only 100MHz and since the PCI and AGP speeds are calculated based on the FSB, they too are overclocked. This may result in damage to your graphics card and/or whatever PCI cards you have in your system.
When the FSB is clocked at 100MHz, the AGP port runs at 66MHz (2/3 FSB speed) and PCI cards run at 33MHz (1/3 FSB speed). At 133MHz FSB, this means approx. 88MHz for the AGP port and approx. 44MHz for the PCI bus. As you can see, this is quite out of spec. I guess you could have done better (and cheaper) buying a Celeron 1GHz. At least that's my opinion.

 

[Gepl]

I'm very well aware that BX chipset and AGP are "a little" overclocked in my system setup, but PCI is running at specified 33 MHz! I think such setup should work fine for quite some time. I'm told that NVidia GeForce handles higher fsb without too much sweat. Furthermore, computer case is well ventilated and Enermax 330 W PSU does its job quite excellent... I actually bought a 900 MHz Celeron and exchanged it for P3 from another system.

 

[Wik]

It must be a memory thing. My P2B used to run just fine with 2 sticks of 128 running a Piii 1000.

Also, there is a 1/4 divider for the PCI so it is at around 33mhz when clocked to 133mhz FSB. Exchange your memory, and use only 2 sticks. You should be fine then.

 

[Gepl]

Memory status update:

I've tried out two pairs of 256 MB dimms manufactured by KingMax and Transcend (JetRam). They were unfortunately specified as CL3 at 133 MHz, although KingMax gave me a little hope it'll operate at CL2. They passed the MemTest ok at CL3, but failed at CL2.

I then looked a little closer at my Microns and found out that two sticks have exactly the same chips (there's a 4-2 mark in the upper right corner), but the third dimm has 1-2 mark. They all have "-75B" in the lower right corner and ctSPD reports the same timings for all of them. Hmmm.

I'll stick with two of them for a while. CL2 @ 133 MHz boosts up the performance quite a bit!