Ask Dan: Which chipset for quad-core overclocking?

Date: 27 October 2007
Last modified 03-Dec-2011.


After seeing your beast of a monitor and watching for specials, I was lucky enough to get one for $500 off (the cost was still obscene, but hey, a bargain's a bargain). Trouble is, my poor Athlon XP 1800+/Radeon AIW-7500 combination can't quite keep up. Five years is a long time with only hard disks and a DVD burner for upgrades, and I think the time has come to retire the old girl to torrentbox duty.

So. Quad Core G0 SLACRing (look Ma, watch me type these letters and numbers like I know what they mean!) seems to be what all the cool kids are doing, but I'm also interested in this SLI business, and would rather not choose between them.

I'm looking intently at the Abit IN9 32X-MAX Wi-Fi nForce 680i board, but am concerned that y'rverygoodfriends say that it's not suitable for quad core CPUs. I've also heard rumblings that the 680i chipset has a slight case of the gremlins.

First question: Is this board going to be significantly worse, overclocking- or other-wise, than a P35 or X38 one?

Second question: Is there a reason that nobody seems to go for (or offer as standard) 3Gb of RAM these days?

My understanding of this whole asymmetric/dual channel thing was that, as long as you put in matching pairs of sticks (say 2x1Gb + 2x512Mb) then all would be copacetic. Before you ask, the SLI would only involve 320MB 8800 GTSs. And you'll be glad to know I was one of the readers hugging themselves and muttering about UMB, HIMEM and EMM386 settings during your otherwise excellent explanation of the 3GB limit.

Thanks for your time (and for helping me put together my last computer).


Some earlier nForce-680i-chipset motherboards (and some earlier BIOS versions for current 680i boards) may have genuinely misbehaved badly with quad-core CPUs, but I'm pretty sure those bugs are all ironed out now (he said innocently).

(After this page went up, Aus PC Market told me that they've had plenty of customers who tried to run a quad-core CPU on a 680i board with 4Gb of RAM and found the darn thing wouldn't work even at stock speed. With 2Gb of RAM it worked, but with 4Gb something was running out of juice. Apparently current 680is can run 4Gb if you bump up the northbridge chipset voltage a little.)

Even if you get a perfectly bugless 680i board, though, you'll still want something else if you're interested in running a Core 2 Quad CPU at higher than stock speed.

Which is a bit of a bummer if you've also got your heart set on dual Nvidia graphics cards in SLI mode, because thus far Nvidia have only allowed that on motherboards using one of their chipsets. I don't think there's any actual technical reason why only Nvidia-chip boards are "SLI Certified", but at the moment, that's the deal. There are rumours that Intel will buy an SLI license for one or another of their chipsets at some point, but it hasn't happened yet.

680i boards are SLI certified, and they can overclock dual-core chips perfectly well, which is all you need for even a quite extreme game PC. But most 680i boards have trouble managing the high bus speeds needed to get the same kind of overclocks out of quad-core CPUs.

Because Aus PC Market confidently expect that almost everybody who buys a quad-core chip from them wants to run it at a million zillion megahertz, they just slap a "not suitable for quad core" label on every 680i mobo, to stop people from trying to get warranty returns on their hardware because it won't run much faster than sticker speed.

If you're absolutely determined to get an SLI system, then the best bet at the moment seems to be eVGA's versions, three of which (the SE SLI 775 TR, the LT SLI 775 A1 and the SLI 775 A1) are currently (end of October 2007) in available for pre-order on the AusPC site, which means they ought to be in stock pretty soon. North American customers can already buy them from eVGA's online store - here, here and here.

The overclocking difference between 680i and the newer, sexier chipsets wouldn't be such a big deal if it weren't for the surprisingly high overclocking headroom that almost every current Core 2 Quad Q6600 CPU seems to have.

Cranking a 2.4GHz CPU up to 3.4GHz, for instance, is a 42% overclock. That's considerably more than most CPUs have been able to handle without alarming voltage increases and heroic cooling to stop them from burning up. If you can only expect to get a 20% overclock out of your CPU without breaking out the liquid nitrogen, then the motherboard's not going to be under a lot more strain then than it would at stock speed, even if you have to wind up the RAM speed along with the CPU speed.

But 50% overclocks seem to be quite unremarkable for Q6600s, if your motherboard can handle it. And these quad-core processors need twice as much power as equal-clocked twin-core versions, just to start with. So an overclocked quad-core can quite easily need four times as much power as a stock-speed dual-core. The better P35 and X380 boards seem to be able to handle that, but 680i boards generally can't.

The absolute redline for SLACR-stepping Q6600s with ambient-temperature cooling seems to be around 4GHz, but the sane ceiling speed is more like 3.8GHz, which is a 58% overclock.

If you've already got a 680i-chipset motherboard with a dual-core chip on it and less than 4Gb of memory and feel like upgrading to quad-core, then go ahead - as long as you're running the latest BIOS version, the new CPU should work perfectly well at stock speed, and it'll probably be happy with a moderate overclock too.

But if you're buying a whole new Q6600-based PC with the intention of overclocking, getting a P35 or X38 board will improve your odds.

For best value for money, get a P35 board that accepts DDR2 RAM. X38 by itself doesn't add anything important at the moment. Yes, you get a PCIE v2.0 video card slot which can move data to a PCIe v2.0 graphics card twice as fast, but that's just another graphics card interface speed bump, and those have been pretty much irrelevant since the distant dawn of AGP. PCIe v2.0 graphics cards will work fine with the PCIe v1.1 slots that other current motherboards have.

(And then there's XMP memory, which is, if you ask me, a pile of marketing wank.)

The extra bus speed of DDR3 RAM would be nice to have if the memory cost little more than DDR2, but it really, really doesn't. Two 1Gb Corsair XMS2-6400 DDR2 modules, suitable for use at any bus speed a modern DDR2 motherboard can manage if it's not submerged in chilled mineral oil, will cost you a princely $AU132 delivered these days (Australian shoppers can click here to order that pack!).

The cheapest XMS3 DDR3 two-by-1024Mb kits, though, are currently $AU451. That price difference is about enough to buy you an extra 750Gb hard drive.

If I were buying a CPU-mobo-and-RAM package today, I'd get Aus PC's slightly discounted combo pack with a Q6600, Gigabyte GA-P35-DS3P P35-chipset motherboard and 2Gb of Corsair RAM for only $AU698.50 delivered. Australian shoppers can click here to order it. It's got two RAM slots free, so you can add another single 1Gb or pair of 512Mb modules if you like.

If I were buying a whole new PC today, though, I... wouldn't. I'd wait about a week. That's because anybody who plans, like you, to buy a couple of 8800 GTS cards, will soon be feeling thoroughly ripped off.

When I first put this page up, on the 27th of October, 2007, a GeForce 8800 GTS (or two if you're greedy) certainly was a good value almost-as-fast-as-possible graphics option. But a few days later, GeForce 8800 GT video cards hit the market, here in Australia and elsewhere in the world.

Early reports put the 8800 GT at about 8800 GTS speed for a few tests, but quite a lot faster for many others - both DirectX 9 and the still-largely-irrelevant DX10. The GT also handily beats ATI's flagship Radeon HD 2900 XT, by margins ranging from the noticeable to the embarrassing.

And the 8800 GT is pretty cheap. Aus PC Market started out with a selection of five differently branded but all essentially identical 512Mb 8800 GTs, ranging in price from a high of $AU379.50 delivered for a Gigabyte-branded model, to a low of only $AU343.20 delivered for a "Galaxy"-branded one.

(If the Galaxy's out of stock, a Gainward-branded card only costs $AU1.10 more. Australian shoppers who'd like to order the Galaxy can click here to do so; for the Gainward, click here!)

The cheapest 320Mb 8800 GTS cards are still sitting around the $AU400 mark, and Radeon HD 2900 XTs over $AU550. If you buy one of those now, you're a mug.

The GT is actually close enough to GeForce 8800 GTX performance that I bet most GTX owners wouldn't notice if you swiped their super-card and replaced it with a GT. There's still some justification for wanting an SLI pair of GTs, but even if you've got a huge monitor, a single GT may well be more than enough.

The only thing that surprises me about this is how long it's taken. The 320Mb GeForce 8800 GTS has been the sensible people's super video card for a solid eight months, now. That's approximately forever in video card years. Only now does something faster and cheaper come along.

(The GeForce 8800 GTX/Ultra is, of course, even freakier - it's been sitting at the top of the graphics card performance charts for almost a year now. The reason for that is, at least, pretty clear - in the original GTX, Nvidia made a video card with performance about a year ahead of what the available fabrication technology could handle. That's why GTX/Ultra cards are such huge, power-hungry, expensive monsters. This strategy is usually a terrible idea, but sometimes it works.)

So. If you're buying a new 3D gaming computer, especially if you've got a big monitor, and you're not made of money, then hold off until your favourite retailer can supply you with a GeForce 8800 GT card, or an SLI pair for use on an Nvidia-chipset mobo.

(If you're really desperate for a new PC, you could buy the new machine video-card-less and use the graphics card from your old PC in it while you wait for an 8800 GT, or perhaps something else like the ATI Radeon HD 2900 Pro, which is an absolutely excellent card with the exceedingly minor drawback that it was announced a month ago and you still can't buy one. Sticking with the old graphics card isn't an option for people like David who're upgrading from an AGP system, though.)

Regarding your second question, about the strangely elusive 3Gb memory mark: I'm not sure why so few dealers offer computers with 3Gb as standard. As I explain in the famous "3Gb barrier" Ask Dan, that amount of memory really is an excellent quantity for PCs these days. 3Gb does give you a better-performing PC than 2Gb if you're doing heavy multitasking or running gigantic games, and it doesn't mean you're wasting money on a 4Gb system most of whose fourth gigabyte is taken up by huge MMIO holes for system hardware like the video card(s).

Soon enough we'll all be running 64-bit operating systems on computers with well over 4Gb of physical RAM and all of this nonsense will be forgotten,

And, as I mentioned in the quad-core CPU Ask Dan (Q6600 CPUs are now only $AU94.88 per core, not the $AU99 they cost way back in July...), the dual/single-channel issue isn't really an issue at all. RAM speed certainly is a bottleneck for absolute PC performance, but few PCs run any software that'll be noticeably slower even if you go into the BIOS and turn off dual channel mode entirely.

You ought to get full dual-channel operation anyway if you install two 1Gb modules and two 512Mb ones. You may even get full dual-channel mode if you install three 1Gb modules - the different electrical "sides" of a single module (which may or may not have RAM chips soldered to both of its physical sides...) can, in theory at least, be connected to different RAM channels.

But if you're a system builder who sells PCs with three memory modules in them, you'll get phone calls from people who're positive that this means they've been cheated out of their dual-channel birthright.

And if you install 3Gb in four modules on a standard four-RAM-slot motherboard, there'll be no room to add any more RAM without ditching some of the memory that's there already (this is, of course, standard behaviour for brand-name computer makers...).

Two-module packs are also now common products from all of the big RAM companies, and as I mentioned above, 2Gb of fast DDR2 RAM is pretty cheap these days. So you're not really wasting that much money if you make a "4Gb" PC that only has 3.25Gb or something available. At $AU132 per two gigabytes, 0.75 gigabytes wasted - and the part of me that remembers $299 512 kilobyte Amiga RAM expanders is as surprised to write this as the same part of you is to read it - is less than fifty bucks.

(Or $459,264, in 1988 A501s.)

Australian shoppers can click here to order Aus PC Market's $AU698.50 Core 2 Quad Q6600, P35-chipset motherboard and 2Gb RAM package.

Aus PC's two cheapest 512Mb GeForce 8800 GT cards are the $AU343.20 Galaxy-branded card you can order by clicking here, and the $AU344.30 Gainward-branded card you can order here.