Ever since we first laid eyes on Shuttle’s original XPC, we’ve been enamored with the concept of small, quiet boxes that still house very capable PCs. You’ve gotta like the combination of stylish design, power, and convenience that such systems bring to the desktopor to the countertop, for that matter. For just about that same length of time, though, we’ve been wishing for a set of standards for small-form-factor systems that would allow DIYers to mix their preferred motherboards with just the right chassis. That desire grew more acute as the popularity of home theater PCs mushroomed, yet building one that’s sufficiently quiet, compact, stylish, and powerful remained a maddeningly tedious exercise in component selection and assembly. Today, small form factor PCs have become a staple offering from big PC makers, but they remain a difficult proposition for would-be DIYers and smaller PC vendors.
AMD aims to remedy this situation with a set of standards, known as DTX, that could bring some harmony to the chaotic, inconsistent world of SFF-ready PC components. The firm first introduced the DTX specification early this year, and we now have our Cheeto-stained hands on a prototype of a DTX-compliant reference design system. Keep reading to see what DTX is all about and how the first reference design is shaping up.
The key thing to know about DTX is that it’s an extension of the existing ATX specification for motherboards and cases, not a wholesale redesign like the ill-fated BTX effort Intel spearheaded a couple of years ago. DTX is also unlike BTX in that it doesn’t seek to accommodate the full range of desktop hardware, such as high-wattage processors or the very highest-end GPUs. Instead, AMD’s spec seeks the simpler goal of hosting relatively power-efficient hardware in a low-noise chassis. To that end, DTX’s peak power envelope for CPUs is 65 watts.
The next thing to know about DTX is that it’s an open standard. AMD has proposed the specification and is actively developing and promoting it, but nothing about DTX requires the use of AMD hardwareother than, AMD would probably tell you, the sheer awesomeness of its low-power processors and chipsets with integrated graphics. Obviously, AMD has an interest in creating a healthy ecosystem for smaller PCs given its position as a supplier of such components, but the DTX standard should easily serve the whole of the PC industry, should it catch on.
The heart of DTX, of course, is a set of specificationsactually, two sets of specificationsfor building components for teensy-weensyand teensy weensiercomputers. We’ll have a look at both sets.
The larger of the two proposed standards is known as Full DTX. As you can see in the diagram above (Don’t you love those words? Ah, the sheer entertainment we here at TR provide for you!), a Full DTX mobo is considerably smaller than a standard ATX motherboardand also smaller than a typical microATX board. AMD has retained the same mounting points as ATX, however, so a DTX board should fit into any ATX case without drama.
At 200 mm wide and 244 mm deep, a Full DTX board leaves room for only two expansion slots, much like a Shuttle XPC. Those slots can be of the PCI or PCIe variety, and DTX provides room for additional expandability via a single, laptop-style XpressCard expansion slot, as well.
AMD estimates Full DTX enclosures will be between eight and 15 liters in volume, and those cases will need to be capable of cooling CPUs with thermal ratings between 45 and 65W. That means no Extreme Edition or FX processors for DTX systems, but it still leaves room for some very high performance CPUs.
Full DTX’s motherboard dimensions will allow mobo makers to produce four boards from one standard-sized PCB panel, AMD reckons. They also expect the mobo designs to require only four PCB layers, like most ATX boards. Both of these attributes should make Full DTX appealing for Taiwan, because they should keep manufacturing costs nice and low.
The second branch of the DTX family tree is known as Mini DTX, and its dimensions are shown above. Mini DTX restricts motherboard depth to 170 mm, but keeps the second expansion slot and accompanying 200 mm width of its DTX sibling. As you’ve probably guessed, Mini DTX enclosures will be somewhat smallerAMD estimates between three and eight liters in cubic volumeand won’t have the same cooling capacity as Full DTX cases. In fact, AMD has set Mini DTX’s upper limit at CPUs with 45W thermal ratings.
The Mini DTX motherboard dimensions should yield six boards per standard PCB panel, but I expect that motherboard designers will have to resort to more than four layers in order to squeeze everything into this space.
While we’re on the subject, we should take a look at how DTX relates to VIA’s Mini-ITX spec, which is popular for embedded systems and other pint-sized-PCs. Well, OK, not exactly pint-sized, but probably less than five liters in cubic volume. At 170 mm by 170 mm, Mini-ITX leaves room for only one expansion slot. AMD estimates Mini-ITX can accommodate CPUs with between 35 and 45W thermal ratings (although VIA’s own processors’ thermals top out at 20W and range as low as 1W, for what it’s worth.)
Because both DTX and Mini-ITX use standard ATX mount points, and because Mini DTX and Mini-ITX are so similar in basic dimensions, AMD believes its DTX push should help establish a chassis standard for Mini-ITX boards, as well.
A look at the DTX reference prototype
Now that we’ve talked about the DTX basics, let’s have a closer look at the prototype DTX reference design system from AMD. This system is still very much a work in progress, but it offers a clear sense of AMD’s vision for DTX. This is, however, very much a reference design. The chassis and motherboard are not early versions of production hardware; although functional, they exist mainly as guides for AMD’s partners.
The hardware inside the box will already be familiar to most TR readers. The motherboard is based on AMD’s 690G chipset with Radeon X1200 integrated graphics. We reviewed the 690G earlier this year. Paired up with the 690G is an Athlon X2 BE-2350 CPU, a low-power version of the Athlon 64 X2 that runs at 2.1GHz and has a 45W thermal/power rating. We reviewed the X2 BE-2350 back in June, and then followed up with a power consumption comparison between the BE-2350/690G combo and Intel’s Core 2 Duo E4300/G965 chipset combo. If you don’t recall the exact details of those articles, don’t worry. The long and short of it is that AMD has a very nice offering in this space, with low power consumption, adequate performance, and better graphicsin terms of both performance and compatibilitythan Intel.
Thanks to its smaller complement of components and what must be a fairly efficient power supply unit, we found the DTX reference box to be even more power-efficient than the previous AMD 690G/BE-2350 pairing we tested. At idle, this box pulls only 44W at the wall socket. When running a 3D graphics demo and two instances of Prime95, it tops out at about 88W. Not too shabby, to say the least.
Here’s a look at the back of the chassis. This box will convert from a pedestal-secured micro-tower to an extra-small desktop within seconds. One need only to pull out the spring-loaded pedestal and give it a twist, so that it tucks away into the side of the unit. Once laid flat on a desk, the DTX box measures roughly 14″ wide, 13″ deep, and 3.5″ high, using my Yankee-style units of measurement. This is a Full DTX affair, by the way. Mini DTX would be even smaller.
The DTX reference system offers up a standard assemblage of ports, with the notable exception of PS/2 mouse and keyboard connectorsthose have been supplanted by USB. Notice that the two expansion card slots will accommodate only low-profile cards.
This system’s prototype status is sometimes readily apparent, like when you attempt to open the cover over the front panel and it tumbles onto the floor, rather than swinging back on a hinge or something. Once the cover is safely lost under your desk, you’ll find a small collection of I/O facilities living behind it, including a slim-line DVD drive, a multi-format flash reader, and audio and USB jacks. In the picture, just to the right of the smart card port is what appears to be a cutout ExpressCard slot. However, there’s nothing behind the cutout in this prototype.
Popping the lid reveals a neat but tightly placed collection of components. This is a very compact design with little room for expansion. Shuttle’s XPCs typically have space for at least one more 3.5″ hard drive, but this box does not.
Notice the ducting around the CPU cooler. The area it encloses corresponds to a set of venting holes in the lid of the enclosure, allowing direct airflow to the CPU fan. Our prototype system is pretty darned quiet after it first boots, quiet enough to sit on your desk without the noise becoming a bother, in my view. And I’m picky. But it’s louder than it should be after it warms up, in part because there’s not another set of venting holes in the lid above the power supply fan. The PSU fan has to work pretty hard to get its job done given the quarter-inch or so of open space between it and the case lid. AMD says it has already tweaked its recommendations to include venting above the PSU fan, so future versions of this design ought to remain quieter during operation.
This angled shot better shows the location of the board’s two DIMM slots, among other things.
The chassis holds the slimline optical and hard disk drives in a metal tray that’s secured by a single thumbscrew and a sliding lock mech. Just unscrew, side the tray sideways a bit, and it pops out.
Beneath the drive tray is AMD’s do-everything front-panel board, code-named Carat 1. This board accepts three internal USB connections and an internal audio header link. From those, it drives the card reader, two USB ports, and two audio jacks.
Here’s a look at AMD’s “Diamond 2” DTX reference motherboard liberated from the case. Holding it in my hands, I was struck by how close the dimensions are to a Shuttle XPC mobo, although the DTX board is slightly wider.
For a quick visual comparison, have a look at the DTX board next to a common microATX board, the 690G-based Asus M2A-VM HDMI. With room for four expansion slots, the mATX mobo is considerably larger.
What about motherboard and chassis makers?
AMD’s DTX reference design looks promising, but the real test will be whether the specification earns the support of motherboard makers, chassis makers, PC builders of various sorts, and the larger industry. AMD lists a whole range of big names in the motherboard and enclosure businesses as DTX partners, so I asked around to see what they had in store. Here’s what I found.
- Albatron Albatron has developed a Mini DTX board, the KD690-AM2, based on the 690G chipset. This board is derived from a Mini-ITX design, the KI690-AM2, but adds enough width to accommodate an additional PCIe x1 expansion slot. The mobo includes two SO-DIMM slots for mobile-style DDR2 memory modules, a GigE port, HDMI and DVI outputs, and eight-channel audio. Albatron doesn’t list the KD690-AM2 on its website because it’s not mass-producing the board. The company says it’s “waiting for the DTX standard to gain more interest in the market” before it commits to mass production.
- Asus As one of the big dawgs of the motherboard world, Asus has plans for DTX products, with projects underway. The firm says it plans to have products available upon DTX’s official launch, but wasn’t ready to share any information with us yet about product specs, features, or positioning. In addition to motherboards, Asus will probably build DTX-based SFF barebones systems, but not stand-alone cases.
- MSI The folks at MSI have cooked up a DTX motherboard, the K9AGMD, based on the 690G chipset. We don’t have much info on it yet, but interestingly, they did say it will cost more than a microATX board. MSI classifies K9AGMD as “in production” and says it is available by request. That means the board isn’t being mass-produced, but MSI will produce them if a large customer places an order for them. Uniquely, MSI said it believes there is an interest among PC OEMsthe big PC makers of the worldfor DTX products, but it couldn’t say which ones or how many might be interested.
- Shuttle The leading light of the SFF PC movement does indeed have a DTX project in the works, currently in the R&D stage. Unfortunately, Shuttle didn’t get back to us with additional information on its DTX project in time for publication.
- Thermaltake Thermaltake actually showed its DTX chassis, the HTPC-oriented DH201, at Computex. This box includes a 4.3″ touch screen on the front panel, a remote, and two expansion slots. Although it’s a Full DTX chassis, it can hold a Mini DTX board, if needed. Like AMD’s other would-be partners, Thermaltake is taking a cautious approach to DTX. They say: “The product, however, is only at the evaluation stage so far. Further market reaction might affect the product development plans in the future.”
We also inquired with Gigabyte and SilverStone about their DTX projects, but they didn’t get back to us in time to be included in this article.
Intel’s take on smaller PC form factors
One company that knows a thing or two about introducing standards for PC form factors is Intel. In fact, the DTX story begins, in some ways, with the market failure of another PC form factor standard proposed by Intel.
Back in 2004, Intel proposed the BTX standard as a guide for building quiet systems with adequate cooling for the fastest desktop processors. BTX wasn’t focused only on small PCs, but the spec included provisions for SFF systems. With its emphasis on system-level integration of measures like an air tunnel for improved cooling and acoustics, BTX was very much a different animal, not just an extension to the existing ATX infrastructure. Producing entirely new motherboard and chassis designs for a new standardwith different mounting points and different cooling provisionsisn’t cheap, so the uptake for BTX was slow. BTX did experience some success, especially with large PC OEMs. Shuttle even built a BTX-based XPC chassis. But much of the market balked.
At the time, BTX was widely seen as Intel’s attempt to address the power and heat problems caused by its Prescott processors. Tellingly, Intel dropped BTX from its roadmap in mid-2006 and stopped promoting it, just as the much cooler Core 2 Duo processors were set to debut.
So I had to wonder: what does Intel make of DTX? To find out, I spoke with Peter Brandenburger, Small Form Factor Program Manager in Intel’s Platform Application Engineering Group. Interestingly enough, Intel’s reaction to DTX isn’t quite the sort of all-out opposition one might expect from AMD’s larger rival. In fact, although Mr. Brandenburger didn’t take a position specifically for or against DTX, he did have some positive words for DTX or something like it.
First, he said Intel still believes in standards for this sort of thing, which is an important endorsement in light of Intel’s BTX experience and the propensity of big PC OEMs to develop proprietary SFF system designs. Also, he classified DTX as a microATX-compatible spec, which, he said, “is what the market wants.” In fact, he noted that Intel itself proposed a similar FlexATX specification (the basis for the original Shuttle SV24 motherboard, as it happens) back in 1999. FlexATX didn’t take off at the time, he said, but with the increasing integration in today’s PCs, DTX might fare better.
Still, Mr. Brandenbuger pointed out that AMD may have difficulty achieving wide adoption for DTX for a number of reasons. The fundamental problem is that there doesn’t seem to be any industry-wide collective agreement or any single answer about how to approach smaller form factors. On one hand, Full DTX may find itself squeezed from above by microATX systems that allow for additional expandability. On the other, Mini DTX’s second expansion slot may not make it an especially compelling alternative to the existing Mini-ITX options.
The key things I took away from my conversation with Mr. Brandenburger were that Intel has thought extensively about small form factor PCs, and that it doesn’t have any major objections to the provisions of the DTX spec. That’s no ringing endorsement, but it is a good sign. AMD seems to have done its homework. As a result, Intel may allow room for DTX to flourish, should AMD’s efforts begin to get some traction. Currently, though, AMD is still very much on its own. Intel has no plans for DTX products, and none of the manufacturers we contacted had plans to build DTX-sized motherboards for Intel CPUs.
Nearly every motherboard and chassis maker we contacted for this story had a similar position on DTX. Publicly, they have all announced support for the standard, usually in the form of a single product or project, in conjunction with AMD’s efforts. Privately, they are hedging their bets, waiting to see whether DTX gains any momentum in the market before committing to producing anything in volume.
One source at a major motherboard company indicated to us that the DTX push needs more focus and clarity from AMD on the question of whether the first products should focus on mainstream SFF desktops, home theater PCs, or some other segment of the market. The same source pointed out that history tell us DTX needs support from chassis makers, even more than motherboard manufacturers, in order to succeed.
Time and again, we heard manufacturers tell us they are waiting for someone else to make the leap in support of DTX. And, realistically speaking, they’re quite credible in saying that they’re ready to produce motherboards and the like when the market demands them. They’re just waiting for somebodyAMD, big PC makers, their competitors, the press, whomeverto make the first move.
I don’t expect that first move to come from large PC OEMs, for what it’s worth. They seem to be doing quite well with designing their own proprietary SFF systems, and a broadly accepted standard would only invite more competition from smaller players. AMD couldn’t name a single OEM that was backing the DTX push. Then again, we don’t really deal often with large PC makers around here, so I haven’t been able to get a clear read on their intentions.
Obviously, it’s early still in the life of DTX, and AMD is still in development with its own reference design. I expect attitudes to change as the development process continues. At some point, the first mass-produced DTX products will arrive, and the industry will be watching to see how they fare. If they do well, others will follow.
The arrival of a DTX prototype system in Damage Labs is, among other things, a trial balloon. AMD and its partners are watching to see how the public reacts to the DTX story, so they can drum up some support and plan their next moves. For my part, I like the DTX concept, and I think the DTX reference prototype is a good start. As a PC enthusiast, I’d like to see a little more room for expansion of certain typesspecifically, a second hard drive and full-height PCI/PCIe cards, both of which Shuttle has managed to shoehorn into its XPC cases. Both things could be accomplished within the scope of the Full DTX spec, probably in a case of this size. Beyond that, most of the things I want from DTX are the same things I’d want in a full-sized PC: reasonably full-featured motherboards with decent overclocking options, truly high-fidelity audio, quality power supplies, good acoustics, and reasonable component prices. Compromises are inevitable with a system of this size, of course, but being able to choose the trade-offs for oneself when building such a system would be priceless. We stand ready to review DTX motherboards, cases, power supplies, and all the rest, just as soon as somebody makes the first move.