Posted Jan 29, 2004 from homelanfed.com
Power, Power Everywhere, But Not a Volt To Drink?
Throughout the growth of the personal computer in the 80’s, 90’s, and now in the 3rd millennium, it has been a design that not unlike humans has had to endure some growing pains every now and then. Though format wars such as those between DVD + and – are often the most recorded of such growing pains, the PC has seen a much more constant pain in the form of power consumption and heat generation. With the greater computing power that computers have gained, the need for more electricity (and by extension more heat dumped out) rears its head out every few years, and those few years have once again rolled around.
Since the creation of the ATeXtended(ATX) specification back in the 90’s, it has required some minor revisions every now and then to keep up with power consumption, and such changes are pretty quiet. Besides the recent creation of the EPS12v standard(more on that later), the last major revision was the addition of the ATX 12v connector, the small 4pin square connector originally needed to provide extra juice to the then-new Pentium 4, and since then adopted by Intel and AMD alike. Since 2002 however, the ATX standard has run in to some issues related to power that it was never originally intended to cover in depth: video card power. We first saw this problem back in 2001 when 3dfx was showcasing its power hungry Voodoo 5 line, which with the high-end V5 6000, needed its own external “Voodoo Volts” power supply. But with 3dfx’s death, the issue was buried once again until 2002, when ATI released the Radeon 9700.
With the 9700 out and ATI not going the way of 3dfx, it became a real problem that had to be dealt with, more so once the GeForceFX 5800 hit the streets also needing a power connector. The unfortunate side effect of this is that the arms race between ATI and Nvidia has been spilling over in to motherboard and power supply design, and that things only became worse once the AGP Pro slot failed to catch on and Nvidia bumped up their power requirements to 2 independent connectors on the GeForce 6800 cards. This of course lead to the popularity of “dual-rail” power supplies that could power the motherboard/CPU and video card on separate rails, and what evolved is a sort of power anarchy among motherboards, video cards, and power supplies.
To the credit of the ATX group, their has been some effort on their part to reign in on this with the introduction of new standards for PCI-Express parts. While the ATX 12v connector was kept for locality reasons(it can go right next to the CPU, making life far easier for motherboard designers), the 20pin ATX plug was replaced with the 24pin EPS12v plug, which adds another 4 pins to help deliver more power to the PCIe slots(which can deliver more power than their AGP counterparts, up to 75W now) without taking power away from the CPU and other components. Video cards received some special attention here too, with a 6pin PCIe connector created that allows for power supply designers to more appropriately route power instead of having to worry about overbuilding the typically low-power 4pin molex connector to handle the demands of a video card.
However, in making this new standard the ATX group didn’t manage to lay down any plans for SLI or certain adaptors, which is where our anarchy problems today start. The first issue that some people are finding is that with SLI boards comes some new and interesting power distribution requirements. To be completely spec compliant, the second PCIe 16x slot also needs its 75 watts of power, but considering the relative massiveness of that kind of power, there’s no easy way to do it. One way is to simply draw more power from the EPS12v connector, but if we back up for a second, there is that dual-rail design to talk about. Because power and power draw can’t be perfectly balanced among the rails on a whim, the total power a system can use will never be rail1 + rail2, which leads to a problem when a device needs more power than just what a single rail can provide. What we’re seeing then is that with some dual-rail power supplies and even with the high-end ones, is that SLI boards their video cards are favoring the EPS12v connector too much, and that dual-rail supplies can’t provide enough power to the motherboard as a result. This causes a very odd situation where single-rail power supplies with a high amperage rating on their 12v line works better on some of these SLI boards, which is causing a lot of customer confusion, and some resentment. Thankfully for vendors, what’s a new power supply when you’re already shelling out upwards of $1000 just for a board and a pair of video cards, but it’s still a thorny issue.
To the credit of the boys over at Asus, they are taking a slightly different approach to the situation as you can see here, as their SLI board includes a molex plug on the board to help power the second PCIe slot. Unfortunately this hasn’t completely alleviated the problem among dual-rail power supplies, and it’s also encouraging another problem that’s best described as “connector hell.” Compared to just 5 years ago, we now have motherboards that don’t just need an ATX/EPS power plug, but need the second 12v plug, the molex plug, and their video cards(which for the sake of argument we’ll include as part of the motherboard as the larger whole) need the PCIe power connector. For user of a single-rail power supply, this requires just coming up with enough plugs on a strong enough power supply for everything(which thankfully isn’t as hard as it used to be), and it generates a precarious balancing act for dual-rail users. In short, it’s getting to be too hard to just plug in all the power connectors for a computer.
Even the vendors themselves are getting confused and are running in to issues related to all of this. Because not all power supplies come with a PCIe power connector, the design allows for an adaptor that will take molex plugs and let them be adapted to a PCIe connector to allow these older supplies drive new PCIe cards, but the PCIe connector design was built with Nvidia’s power-hungry 6800 Ultra in mind, so it was designed to carry 2 molex plug’s worth of power.
But remember at the same time that the new PCIe standard allows for more power on the PCIe card slot than AGP did, so there’s not as much of a need for that second molex plug’s worth of power; so to save end users some grief, when ATI built the adaptors for their PCIe X800 cards, they designed such an adaptor that takes a single molex, and built their cards in turn to only draw on one rail. Their plan backfired a bit though, as their adaptor wasn’t designed correctly and is missing a ground connector. On the plus side, it’s not the important ground connector that makes the difference between frying the card or not, but on the down side, it is the ground that the card uses to complete a circuit to make sure that the PCIe connector is plugged in. Because of this the card will fail to work thinking that it doesn’t have a PCIe power connection, but the fix isn’t much harder than replacing the cable with a proper one for $10 or so. But for ATI this is a lesson in it not always being wise to try to cut corners no matter the intentions, and yet another exhibit of the anarchy and connector hell problems that are continuing to evolve.
We wouldn’t be talking about this issue if we didn’t have a solution though, so a few people are probably going to cringe right about now: we need another new power standard. Call it ATX+, ATXX(X), ATY, I don’t really care, but high-end home/gaming hardware has worked itself to the point where just like high-end workstation hardware it needs its own standard. At the very least, the EPS12v connector needs to be built to provide more power, either by increasing tolerance or adding more pins, and the ATX 12v connector needs to be built in to the EPS12v connector too. And while we’re at it, increase the amount of power a PCIe 16x slot can provide so that it’s well overbuilt if it has to be, as long as the external power connector is no longer necessary(though I’ll be benevolent and say it can stay for compatibility with mid-range boards that don’t have the extra juice).
Now I’ll be the first person to admit that such a suggestion is about as ugly as they come(my sincerest condolences to the motherboard designs out there), but at this point, do we have much of a choice? High-end computing isn’t known for its falling power needs, and with the movement to dual-core CPUs later this year we’re on the verge of another jump in power usage, so now is as good as any time to try to make a more permanent fix. Otherwise, if we don’t put an end to this power anarchy and reign in on connector hell, how many more people are going to be left having to keep buying unnecessary new parts for their computers just to satisfy their computer’s power needs? The answer is greater than zero, and that’s too many people in the year 2005.
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