EZ-E,
I have been lurking for awhile, and this issue has come up before, but there has only been a partial explanation of the problem.
I will restate the obvious just so future responses won't be so spiteful:
The GA-965G-DS3, as the name suggests, is based on the G965 Express chipset, and the GA-965P-DS3 is based on the P965 Express. The difference between them is that G965 chipset includes on board video provided Intel's new GMA X3000 graphics chip.
For some reason the 965G-DS3, regardless of BIOS version, has a hard time accepting changes to its BIOS settings, and for some reason can't produce stable overclocks anywhere near the the 965P-DS3. One partial reason seems related to the use of the on board video. Folks report very limited wiggle room on the FSB when using the integrated graphics. When the board finds a videocard in the X16 slot it is supposed to disable the on board graphics. When using a separate video card some OCing should be possible.
Next, if you hunt around on some other enthusiast forums, for example try this link:
http://forums.anandtech.com/messageview.aspx?catid=29&threadid=1926179&frmKeyword=&STARTPAGE=2&FTVAR_FORUMVIEWTMP=Linear
you will find that some people report that they are able to get decent overclocks when they use Gigabyte's EasyTune windows applet, but the same settings won't even POST when they're set in the BIOS. Some of these folks, who are clearly not newbs, felt cheated and frustrated by the 965G-DS3, and so exchanged theirs for a 965P, and they were much happier, as the same RAM, CPU (usually a C2D E6300 or E6400), and videocard produced results on their 965P-DS3 boards that was the same as everybody else.
My experience:
This setup is my secondary system, because I need reliability more than I need speed in my primary setup, so I no longer tweak that setup, and my old backup Prescott P4 system suffered a motherboard failure, and it wasn't worth putting any money into a socket 478 system.
GA-965G-DS3 (rev 1) BIOS F7
Intel 805D @3-3.4 Ghz, 1.335-1.500 volts, Intel stock cooler with AS5
2 X 1GB PNY DDR2 677 (4-4-4-12) 1.9 volts
PNY 7900 GS 256MB
2 X 250 GB WD SATA HDs (no RAID on them)
A really old Soundblaster Live! card (which, surprisingly, still sounds better than the onboard sound)
Antec 500 W PSU
Win XP Pro SP2
I started putting this rig together early last fall, which is why I have a rev. 1 board. As I was cutting every corner I couldn't afford a a C2D E6300, so I went for the 805, because it was highly OCable. I was able to get the same production version that Tom's had used in their test to go to 4 Ghz for $90, so I did that.
Even with the newest update I cannot seem to get FSB and memory timings to work from the BIOS setup. However, when I use the EasyTune App, I can monkey around quite a bit. At a CPU voltage of 1.335 I can raise the FSB to 162 (the 805 has a base of 133), the memory to 660 and the system works fine, and the heat is manageable. I can go higher, but the CPU overheats with the lame Intel cooler. None of the settings that produce a stable overclock in Windows can even produce a successful POST when done from the BIOS.
Unfortunately I'm low on free time these days, as I'm trying to make some headway on my PhD dissertation, so I don't have much more help to offer.
Try the EasyTune applet and post your results, I'd love to know how it behaves with your C2D, as I plan on upgrading when the 4 meg cache version of the E6400 comes out.
Later
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AMD FX-55 (clawhammer)
Asus A8N-SLI Deluxe
1 GB Corsair XMS LL DDR 400 (2-2-2-5 1T)
2 X EVGA 6800 GT or 1 X PNY 7900 GS
Audigy 2 ZS Platinum with Logitech Z-5300 speakers
2 X Maxtor 160 GB SATA HD (RAID 0)
1 X Seagate 750 GB SATA HD
NEC 3540 DVD R/W
Silverstone Zeus 650 W PSU
Silverstone TJ-5 case
Viewsonic VP201b
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