Is it possible to create a 10W gaming PC?
14th Apr 2013 | 11:00
Low power to the people
While phones and tablets can idle at sub-watt levels, even a modest PC gaming rig can happily suck down almost 200 watts of power without trying.
If you're sat there browsing the web or furiously writing complaints about the neighbour's leylandii, all that power seems a bit of a waste of energy.
But what are the alternatives? You could jump on your laptop, but that's often still underpowered and you're left with an awful keyboard and trackpad to use, while upgrading it always feels a compromise.
But then we did what our therapist told us not to do, we got thinking, perhaps we could build a full-desktop system that was capable of 3D gaming but was also built around the idea of ultra-low power consumption? Perhaps even low enough to rival a laptop?
At the heart of this project is going to be the new breed of Intel Ivy Bridge processors. They're built with a 22nm process and, in some ways most importantly of all, Intel's new generation of integrated HD Graphics, which means we can do away with power hungry third-party graphics cards for our system. Sorry AMD and Nvidia.
With so much integrated on to the super-efficient 22nm process, low-power states can be efficiently managed. While historically higher-power tasks now require far less juice as well, this is against a background of continued integration and ever more efficient processes; the number of ICs on a motherboard is down, the main chipset uses less power than ever and main storage and memory can be measured in a single watt. So let's see if we can get near that magical 10W mark…
The road to power efficiency
When you think of PCs and power, you're more than likely thinking 800 Watt power supplies, 125 Watt TDP processors and multiple graphics cards, each of which could probably suck down enough juice to power a small English hamlet. That view of the PC world does exist and isn't even that uncommon.
Even a modest gamer is going to use a system that's sucking its way through a couple of hundred Watts under load. Never mind someone like Jeremy Laird that's running Intel's latest six-core Extreme Edition kit. You don't even have to go to those extremes to rack up a multi-Watt power tally.
Everything in a system adds up to the final power usage. From all the ICs on the motherboard to multiple DIMMs in their many slots, to arrays of RAIDs, every component adds to the overall power draw. While the headline components like the processor and graphics card consume by far the most power, as we'll see when we start chipping away at the power consumption, suddenly every Watt of power becomes an issue.
We're not trying to demonise PC gamers and users here. On the contrary we love the high-powered rigs and the fact is these days the components comes with reasonable power savings, enabling them to power down usually to a single Watt making them more environmentally friendly than ever. The question we're asking is: can we have a decent desktop PC that's capable of modest 3D gaming with the latest games, but one that would have trouble powering an energy-efficient light bulb?
Now that Intel has finally gotten around to producing usable integrated graphics, the answer to that question seems to be an emphatic yes. All that remains is figuring out how low we can go in power terms.
So we're going on a voyage of low-power discovery. Taking a look at why individual components have been chosen, why they're so much better than other choices and how they've managed to achieve such a low-power result.
We're going to kick things off as is often the case with the processor but for a couple of good reasons. So we all know that when Intel introduced its Sandy Bridge processors it had finally introduced an integrated graphics solution that was just good enough to play the latest games. Something you could never say about older attempts, which seemed nothing more than afterthoughts to fill out the feature list.
The crucial aspect of putting the graphics on-die with the CPU is that it all has to fit within the TDP of the processor package. The processor is core to system performance, entirely so when you're relying on it to provide the performance graphics end of the system too.
Potentially, both Ivy Bridge and Sandy Bridge processors offer low-power models that could be used within a suitable system, it's just choosing the right one.
The 'older' HD 3000 offers 12 execution units at a higher 650/1250 clock, while the newer HD Graphics 2500 has just 6 at 650/1150. You would think this would lean us towards a Sandy Bridge packing HD Graphics 3000 model, such as the Intel Core i3 2105. But doing so trips you from the 35W TDP into the 65W TDP category as it's built on the 32nm process.
Opting for the 22nm based Intel Core i3 3220T provides a chip that retains a reasonable 2.8GHz speed with its twin cores and Hyper Threading but one that runs within the 35W TDP too. Opting for the HD Graphics 4000 or a faster 3.4GHz model bumps the processor up to 55W TDP. As it also turns out the revised HD Graphics 2500, while running half the number of execution units of the older HD Graphics 3000, manages better performance per-unit than the older model.
If we were going for low-power gold then the Intel Core i3 3217U that offers a tiny 17W TDP but still with an enhanced HD Graphics 4000 would be very tempting, until you realise the GPU clock is crippled at 350MHz. It actually tempted Intel itself, as this is the processor chosen for the Intel NUC mini-PC.
Our main turn-off for this model is the low 1.8GHz main core speed, as we feel the extra 1GHz will benefit us in the long run for general tasks and gaming. If we weren't going for lowest-power then certainly the Intel Core i3 3225 would be of interest.
In a similar frame of mind the name AMD hasn't so far been mentioned at all. That's because unfortunately when it comes to low-power AMD can't match Intel on the fabrication process technology. The AMD A10-5800K can slap the Core i3 3225 around in terms of GPU performance and pricing. But take a look at its TDP and it is 100W against the Core i3 3225 TDP of just 55W, while AMD can't build an A-series processor with a TDP below 65W.
Mummy or chips?
Connected on a certain level with processor power usages is that of its particular chipset and motherboard. In the past motherboard chipsets have been surreptitiously power hungry. This was partly due to them being based on older fabrication processes. Added on top of that, older chipsets had to do a lot of donkey work which has now been integrated onto the more efficient processor die, and let's not forget the benefit of the integrated graphics element.
We've chosen the mid-range Intel B75 chipset, this has a TDP of 6.7W while it offers all the advanced ports you'd be after such as USB 2.0/3.0 and PCI Express 3.0. On a being nice to AMD note its A-series Fusion Controller Hubs or FCH are actually competitive on power, dissipating between 4.7W and 7.8W, this certainly wasn't always the case with the AMD 890GX chipset hitting 22W with its integrated Radeon HD 4290 graphics.
Contrast with say the classic Intel 945 Express, this provided DDR2 dual-channel memory support and was released back in 2005. It had a TDP of 15.2W and had to be accompanied by a South Bridge I/O IC to provide PCI, LAN and USB support. This added another 3.3W for a maximum of 18.5W.
Similarly the Intel 915G with its integrated graphics pushed this to 16.3W with its South Bridge using 3.8W, which topped out at 20W just for the chipset, never mind the processor.
The motherboard we've opted for is the MSI B75IA-E33 mini-ITX based, as we've mentioned, on the Intel B75 chipset. Technically, the Intel Z77 chipset has the same power dissipation but these mobos tend to be fully-loaded high-end affairs and any extra ICs on there will add to the power requirements. So the super-slimmed version works for us just fine. Besides it offers everything you'd want output wise anyway.
We're all aware of gold-rated 85 per cent efficient power supplies, right? Well, turns out they're not, under low-power conditions. That whole gold-standard only applies to a PSU under full load. Hook up a low-power system or just a standard system that's idling along while you, for example, consider your insignificant position in this infinite universe, and it's efficiency will tank.
What does that mean to you? It means that a low-power system ends up sucking down more Watts than it actually needs to and not even by a small amount, as we'll see. For testing we'll be using a gold-standard 850w PSU as a benchmark and older 275w Intel PSU to see how a lower power but unrated PSU can manage.
Lastly, we have a Pico PSU from Scan. This is an especially engineered, low-power PC PSU that is reported to be as high as 96 per cent efficient. Its main disadvantages are that it's limited to 160W, uses an external power brick and has limited connections. While it does offer a full 24-pin ATX connector and the standard 4-pin ATX12v connector, it only offers a single SATA power connector and 4-pin Molex.
There is an even lower-power Pico PSU option that omits the ATX12v connector, but for the modern PC systems we're after that's not an option.
We're not quite done with selecting components for our low-power system. Hard drives can add quite a lot of power consumption to an overall system. In a standard desktop computer a bank of four 3.5-inch spinning hard drives can actually consume upwards of 30 Watts when under full access.
Things are somewhat more subdued once they've spun down at 0.75 Watts per drive. Even SSD drives don't get away with a free power ride here. Power use on SSDs can vary as high as 6 Watts under load. This is as high as a 3.5-inch spinning drive, so thinking it's solid state doesn't necessarily mean it's low power.
In contrast we're also testing a Western Digital Green 2.5-inch 2TB drive. This offers SSD matching power consumption, but without the capacity limitations while the retail price of £150 matches the higher-end 256GB SSDs. The load power draw is a very respectable 1.7w while idle is 0.8w.
The last element we're looking at is memory. Obviously opting for a single DIMM rather than a dual configuration will help reduce the overall power required. Beyond this it's also possible to buy low-power DDR3. For the test we have an 8GB Kingston DDR3L DIMM that's rated at 1,600MHz and 1.35v rather than the normal 1.65v for DDR3.
Didn't he do well
Plugging this all together, and powering it up off our standard test PSU a XFX 850w model, we were pleasantly surprised to read idle consumption of 22W and a game load of 36W. At this point we cracked out our Pico PSU and re-ran the system. Impressively, idle power consumption dropped to 15W an improvement of 32 per cent, while load dropped from 36W to 25W again an improvement of 31 per cent.
There was chatter that lower-power PSUs could fare better, so we tested an older Intel 275W PSU from a BTX system. Clearly the age of the PSU showed through as the power draw of 28W at idle and 39W under load was significantly worse with the Pico PSU being around 47 per cent more efficient.
Of course, these initial results are through running the base BIOS settings. While many of the more useful voltage settings get locked out, we can at least tinker with a few settings. It's odd the DDR3 memory defaults to 1.65V, we had already manually selected 1.35volts, but we also kicked the memory bus down to 1,066MHz from 1,600MHz. We also turned off as many of the on-board integrated chips as possible, such as the LAN and audio.
Annoyingly, many of the voltages and even the QPI bus speed aren't accessible, as we'd certainly be tempted to undervolt the memory controller Vtt line, the memory VDIMM and main chipset PCH line. Underclocking the CPU from 2.8GHz to 2.0GHz had no effect on idle power consumption, we'd imagine as largely the processor powers down as much as possible no matter what the clock.
Surprisingly, it also had no effect on the loaded power consumption. All of this tinkering managed to drop the Pico PSU idle power consumption down to a mere 13 Watts idle and 23 Watts under a gaming load. Even adding the WD Green 2TB 2.5-inch drive to the system wouldn't see this rise above 15 Watts.
As a gaming rig it is going to leave something to be desired in the speed department, but the fact is, this is a system that can game if you need it to. At 13 Watts idle we almost match our plucked-out-the-air 10W goal and frankly brought desktop power consumption down to laptop levels. We think that's pretty impressive, especially as we haven't had to compromise raw CPU power.