Here Today, Gone to Maui? Hands-On with AMD's HTPC Platform

Posted 05/12/2009 at 4:30pm | by Michael Brown

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Sorry, we couldn’t resist the headline. For the record: We’re not predicting the early demise of AMD’s new Live Home Cinema reference platform (which is code-named Maui). AMD sent us a sample build several months ago, but we wanted to live with it for a while before publishing our thoughts on the design.

We’re big fans of home-theater PCs, especially the build-it-yourself variety (be sure and check out the May issue of Maximum PC for Will Smith’s terrific how-to guide to building one of your own). If AMD can resolve one major issue, we think Maui will be the best home-theater PC platform on the market.

With a home-theater PC, you can stream all manner of Hollywood content for free (from websites such as Hulu) or for a small fee (from online stores such as iTunes, Netflix, and Amazon’s Unbox). While you can accomplish the same thing with a media center extender and any PC equipped with a version of Windows that includes Windows Media Center, a dedicated HTPC leaves that other machine available for other tasks. A home-theater PC with a Blu-ray drive can play HD movies, too, but comparing home-theater PCs to Blu-ray disc players—which are becoming increasingly PC-like—is more problematic. We’ll get to that soon enough; for now, let’s take a detailed look at AMD’s Live Home Cinema platform.

The hardware to build this particular AMD reference design would cost around $900 at retail. It’s based on an AMD Phenom X4 9350e quad-core processor plugged into an MSI MS-7411 micro-ATX motherboard (which MSI markets as the Media Live Diva). The MS-7411 uses AMD’s RS780M/SB700 chipset with an ATI Radeon HD 3200 integrated graphics core (the RS780M is a mobile, low-power version of AMD’s RS780G chipset, with added support for component video output). AMD stripped all legacy components (except VGA) from the motherboard’s design; you won’t find serial or parallel ports, PS/2 mouse or keyboard ports, or even a PCI bus. 

Cool Running

The CPU is cooled by a closed-loop cooling system, the Noise Limit SilentFlux Media heatsink and fan. The SilentFlux boasts a very low profile that’s optimized for horizontal installations, such as a home-theater PC: Its radiator rises just 2.36 inches above the CPU. It’s also extremely quiet, with a stated noise level of just 21dB. We didn’t encounter any problems running the PC in our enclosed entertainment center, even those times when we forgot to turn on the ceiling-mounted cooling fan inside there.

AMD shipped this evaluation system with 2GB of Aneon DDR2-667 memory, a Pioneer BD202MR Blu-ray, and a 500GB Seagate Pipeline HD hard drive.

Awesome Audio

The Maui design’s biggest claim to fame is the presence of a D2Audio DAE-3 digital audio engine, which can output 2.1-channel analog audio from the motherboard. Alternatively, you can pair it with either a five-channel amplifier card or a seven-channel pre-amp card. D2Audio designed both these components, and AMD sent both for evaluation. If you buy MSI’s Media Live Diva 5.1, you’ll get the amplifier card; purchase the Media Live Diva 7.1 and you’ll get the pre-amp card.

The amplifier delivers up to 100 watts per channel to passive speakers (you connect your eight-ohm speakers directly to the card, there’s no need for an A/V receiver or even powered speakers—other than a powered subwoofer, of course). The amp delivers an impressive signal-to-noise ratio of 105dB and total harmonic distortion (THD) of less than 0.5 percent. It will drive four-ohm speakers, too, in which case it will deliver 200 watts per channel. You’d have to spend a great deal of cash to find a stand-alone amp with comparable specs.

The pre-amp card boasts an even higher signal-to-noise ratio of 110dB (with 0.5 percent THD) while adding support for a pair of rear surround channels. You connect this card to your A/V receiver (or powered speakers) using conventional RCA cables—there’s no need for funky adapters or anything else in the signal path. Alternatively, AMD’s RS780M chipset can deliver compressed 5.1-channel digital audio over HDMI. The reference design also includes a Realtek ALC888 audio chip on the motherboard that delivers digital audio over a coaxial S/PDIF connection (optical S/PDIF is not supported).

Can’t Get There From Here

Most people considering a home-theater PC will be looking to play Blu-ray movies, and this is where AMD’s solution (indeed, all PC solutions) falls short. There’s no problem getting high-definition video to your display: You can use either HDMI (integrated into the motherboard, so here again, you don’t need an adapter) or component video cables (although you might have a problem transporting DRM-protected video over component cables). The problem lies in the audio realm, an area in which this solution is otherwise absolutely marvelous. It has nothing to do with technological limitations and everything to do with the D-word (DRM, or digital rights management).

The AACS (Advanced Access Content System) copy-protection system used to encrypt Blu-ray discs dictates that Blu-ray player software (e.g., Cyberlink’s Power DVD Ultra) must use a so-called “protected path” to send high-definition audio (e.g., losslessly compressed Dolby TrueHD or DTS-HD Master Audio) across a user-accessible bus such as PCI or PCI Express. The objective is to prevent anyone from intercepting the unencrypted audio and making a bit-perfect copy. The Blu-ray video bit stream is subject to the same restriction, but the Windows ecosystem is capable of handling this.

The D2Audio chip on the Maui platform uses a closed, proprietary bus, so it does seem to be in compliance with AACS. Unfortunately, AMD has so far been unable to convince any of the companies developing software Blu-ray players to send unencrypted HD audio over that bus.

The work-around is for the Blu-ray software player to decode the losslessly compressed audio, down-sample the bit stream from its 96kHz sampling rate with 24-bit resolution to a 48kHz sampling rate with 16-bit resolution, and then pass the uncompressed eight-channel LPCM (linear pulse code modulation) bit stream to the D2Audio chip. The D2Audio chip converts the bit stream to analog and sends it to the pre-amp card, the motherboard’s line-level outputs, or the amplifier card. The D2Audio chip does not pass digital audio of any form over HDMI.

Needless to say, down-sampling is less than an ideal compromise. Then again, the mere availability of a movie on Blu-ray disc doesn’t automatically mean that it has a Dolby TrueHD or DTS-HD Master Audio soundtrack or that it’s encoded using the highest possible specs. You’ll encounter many films with audio encoded at a 48kHz sampling rate with 24-bit resolution, for instance, and many more that are encoded at a 48kHz sampling rate with 16-bit resolution, at which point down-sampling isn’t even necessary. The website CinemaSquid maintains a comprehensive searchable database of Blu-ray releases that includes such information.

Many people will contend that the average consumer can’t tell the difference between HD and lesser audio—but who’d be willing to spend $900 or more for a PC that can’t offer one of the features that a $300 Blu-ray player can. In our book, audio quality is the second biggest reason to buy any hardware that’s capable of playing a Blu-ray disc and Maui represents a compromise on that score—whether we can hear it or not is moot.