I bought a Gigabyte EP43-DS3L last summer and originally put in 2x2GB Memory sticks. I used matched Patriot DDR2 1066, 5-5-5-15 (PDCG248500ELKR2) at the default speeds/BIOS configs in Dual Channel mode.
Everything worked just fine. Then I decided I needed 8GB, so I tried to track down another 2 sticks of the same memory. I found the Patriot Viper PV224G8500ELDB at Fry's, which is also DDR2 1066 5-5-5-15. It has a different packaging/heatshield, but I figured it wouldn't be a problem, since it's another Patriot matched set running in another channel, with exactly the same timing & specs.
Because of clearances with my CPU heat sink, I couldn't fit the new memory in slot 4 (the Viper memory has heat sink fins).
So I put the ORIGINAL memory in slots 2 and 4, the NEW memory in slots 1 and 3. The mobo recognized 8GB, but then immediately boot-looped when starting Windows. I suspected bad memory or issues with the (slightly) different memory sticks in each channel, so started troubleshooting.
So I went back to where I started. I took out the NEW memory and put the ORIGINAL memory back in slots 1,3. The machine booted fine. [phew...]
Then I checked the NEW memory in slots 1,3. Again, the machine boots fine with 4GB of the new memory [Curious... both sets of memory worked fine in slots 1,3]
Then, I put the ORIGINAL memory in slots 2,4, with 1,3 empty. The machine boot loops.
Basically, any time I have somtthing in channel slots 2,4, it's unstable, even though that same memory works fine in channel slots 1,3.
To troubleshoot a bit more, I ran memtest86+
The original 2 sticks of memory in dual channel mode: [2GB in Slot DDR2_1, 2GB in Slot DDR2_3] Memtest passes 100%
Then I took one stick of memory that passed memtest in dual channel mode and moved it from slot to slot, isolating one 2GB stick in single channel mode.
Slot 1 [2GB in DDR2_1]. Memtest passes 100%
Slot 2 [2GB in DDR2_2] Memtest fails immediately. Within a short time, memtest terminates with an exception.
Slot 3 [2GB in DDR2_3] Memtest passes 100%
Slot 4 [2GB in DDR2_4] Memtest fails, but not as quickly as in slot DDR2_3. after 50% of the tests, there were a handful of errors.
It seems to be an issue with the 2nd and 4th memory slots. Motherboard issue? I have the latest BIOS... running at default BIOS default timing (5-5-5-15, 1.8V).
The two slots I originally populated w/ 4GB work fine. The second pair of slots (2,4) seems to be hosed. Anyone seen this before? What a bummer of a hidden defect.
Manual says 1,3 or 2,4 are both valid dual channel memory configurations. Anything else is a valid single channel configuration, so it's looking like an RMA situation with 2, 4 not working. It's a Gigabyte motherboard, I've put in the request & I'll report back what they say.
Well, good luck, we had a post yesterday at the forum about one person going through three techs and a week before the board was RMA'd, if I can recall it had something to do with a graphics card running at x8 PCI-e lanes with usb3 and other SATA ports disabled on a Gagabyte P55 board.