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785G memory errors *only* in dual channel

Knavish

Knavish

Senior member
I've got an MSI 785G motherboard and 2x2GB DDR3 memory. (No OCing & timings all set to default.)

Using Memtest86:
1. When I run either memory stick by itself I get no errors.

2. When I run both sticks in dual channel, but UNGANGED mode I get frequent errors (and random crashes in Win 7).

3. When I run both sticks in dual channel ganged mode, I haven't gotten any memtest errors yet and the system seems stable when I get into Win 7, BUT 30%+ of the time when I cold boot, I get a RAM R/W Error at POST.

Could the on-cpu memory controller be screwy? Or perhaps the motherboard?
 
Knavish what memory are you using? I just bought that MSI 785G board we dicussed in another thread.

I'm now starting to research my memory choices.

Also, did you figure out the issue?
 
rivethead said:
Knavish what memory are you using? I just bought that MSI 785G board we dicussed in another thread.

I'm now starting to research my memory choices.

Also, did you figure out the issue?
Click to expand...

I'm using this memory:
G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Desktop Memory Model F3-10666CL8D-4GBRM - Retail

I haven't solved the problem yet. I may end up buying another set of 2x2GB memory from a different vendor & seeing if it is still unstable. If that fixes the problem, I'll RMA the Gskill & end up with 8GB...

I'm still open to suggestions / troubleshooting ideas.
 
Knavish said:
I've got an MSI 785G motherboard and 2x2GB DDR3 memory. (No OCing & timings all set to default.)

Using Memtest86:
1. When I run either memory stick by itself I get no errors.

2. When I run both sticks in dual channel, but UNGANGED mode I get frequent errors (and random crashes in Win 7).

3. When I run both sticks in dual channel ganged mode, I haven't gotten any memtest errors yet and the system seems stable when I get into Win 7, BUT 30%+ of the time when I cold boot, I get a RAM R/W Error at POST.

Could the on-cpu memory controller be screwy? Or perhaps the motherboard?
Click to expand...

Sounds like either a bad MB or CPU memory controller. The best way to know for sure is to pop in a different CPU or memory sticks and isolate the issue.

I definitely don't advocate purchasing some different dual-channel RAM and testing them if you don't have any extras (or know anyone who does) around.

:sneaky:
 
Knavish:

I don't know if this will help:

"Pros: I chose this particular MB because it was the only 785 that had a heatsink on the mofits. It has firewire and plenty of USB ports. I put an AMD Athlon II X4 620 and was able to overclock it to 3.25Ghz simply by setting the FSB to 250.

Cons: I set my RAM to DCT Ganged Mode thinking that Unganged Mode was a Single Channel mode. When I memtested my RAM, I started getting hundreds of errors. When I memtested in Unganged mode I had no errors. After some research I found that Ganged Mode runs the RAM in one 128-bit bus and that Unganged Mode runs using two independent 64-bit busses (effectively running 128-bit). The AM3 CPU has two memory controllers. I read that AMD recommends running in Unganged Mode and that there are issues with Ganged Mode. I know that some other MB manufacturers are forcing Unganged Mode in newer BIOS releases to deal with this issue.

Other Thoughts: MSI 785GM-E65 AM3
AMD Athlon II X4 620 Propus 2.6GHz
G.SKILL Ripjaws Series 4GB (2 x 2GB) DDR3 1333
Western Digital Caviar Blue 500GB 7200 RPM SATA
Rosewill Stallion Series RD500-2DB 500W ATX12V PSU
APEX TX-381-C Black Steel Micro ATX Tower"

It's from a NEWEGG review of the mobo. I was looking through the reviews to see what people were using for memory, ran accross this and thought of this thread.
 
rivethead said:
Knavish:

I don't know if this will help:

...snip...

It's from a NEWEGG review of the mobo. I was looking through the reviews to see what people were using for memory, ran accross this and thought of this thread.
Click to expand...

Thanks a bunch for the info. I'm going to have to read more about this ganged vs. unganged mode & test them again on my computer. Somehow I was under the impression that ganged mode was faster because it had something to do with interleaving the memory banks. THIS IS WRONG. Apparently in ganged mode, you combine the 2x 64-bit memory controllers on the CPU & access the memory as though you had a single 128-bit memory bus. In unganged mode you have two separate 64-bit controllers, which is better for multiple threads that each want to access memory independently of each other. Benchmarks I've seen show differences between the two, but they've got pretty even tradeoffs even for a single thread. Unganged mode is recommended.
 
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Possible Solution:

I reset all settings in BIOS using the Failsafe Defaults & bumped up the RAM voltage from the default (should be 1.5V according to spec, but it just said "DEFAULT") to the next step higher. It was in the low 1.6V range, like 1.61V.

This procedure reset the memory to unganged mode, btw.

I ran memtest86 overnight (18 passes) and no errors. I guess this means the ram doesn't work at its default voltage. Might still be worth RMAing it I suppose.

I should still run some stress testing in Windows to confirm.
 
Diggin up an old thread; but it looks like this issue was fixed with the newest 2.4 BIOS release. I was having the same problem, where the 785G board would only run reliably while in Ganged using Prime95. After updating to 2.4, I was able to run unganged at stock for 8 hours on Prime95 Blended.
 
artimasz said:
Diggin up an old thread; but it looks like this issue was fixed with the newest 2.4 BIOS release. I was having the same problem, where the 785G board would only run reliably while in Ganged using Prime95. After updating to 2.4, I was able to run unganged at stock for 8 hours on Prime95 Blended.
Click to expand...

I think the BIOS update did help me too, with the ganged vs. unganged thing. Unfortunately I was dealing with both the BIOS problem and a bad sick of GSKILL memory. After patching the BIOS & buying new RAM, everything is 100% stable now.

Now I just got to make time to RMA my bad RAM & figure out how to (potentially) unlock the L3 in my Deneb core 🙂 I've been too busy with work to play with my computer very much the past several weeks.
 
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