So here's the deal. It's a tiny 7 by 7 inches (18 by 18 cm) caseless HTPC (Home Theater PC). I've assembled it this week and since it's so great I decided to share my experience with the rest of the world.
The HTPC is connected over HDMI to a 46 inches Full HD screen. I'm using it for Internet browsing, filez downloading and, of course, media streaming: HQ Audio & Full HD Video.
Considering these objectives, the main requirements from such a PC are:
1. it must be absolutely Noiseless. It should make no sound.
2. minimal electricity consumption.
3. smallest possible dimensions.
4. HDMI support and sufficient processing power
5. low cost
Noise in PCs is coming from the cooling fans, so noiseless PC means no fans. In other words cooling must be totally passive. This requires both a very low power processor and a large and effective heatsink.
The CPU - Intel Atom 330
The processor should run on very low power and yet must be sufficiently powerful. A rather quick search on google led me to the conclusion that as of today (Feb. 2010) the obvious candidate is Intel Atom 330.
Atom is Intel's brand name for a line of ultra-low-voltage x86 and x86-64 CPUs, designed in 45 nm CMOS and used mainly in netbooks, nettops, and Mobile Internet devices. Intel declares that ATOM is built with the world's smallest transistors for low power and designed specifically for a new wave of Mobile Internet Devices and simple, low-cost PC's. ATOM 330 (unofficially code-named Dual Diamondville) is a dual-core processor running at a 1.6 GHz clock speed.
Intel ATOM 330 + Nvidia GeForce 9300/9400M = ION
While Intel's Atom 330 is fast enough for many tasks, it doesn't have the horsepower to handle HD decoding on its own, not even with a second core. The CPU is simply not fast enough to decode high bitrate video (much less H.264) and the chipset doesn’t support HD video decode acceleration.
NVIDIA saw an opportunity with Atom. Intel had a very popular CPU, that could be used in many more environments if it could only be paired with a more powerful chipset. Enter the GeForce 9400M. This is the very same GeForce 9400M that’s in the new MacBook, MacBook Pro and MacBook Air...and NVIDIA was pairing it up with Intel’s Atom processor. ION was born - A GeForce for Atom. ION is capable of decoding and playing full 1080p HD video content with true-fidelity 7.1 audio, thanks to GeForce 9400's PureVideo HD decode engine that offloads large portions of the decode process for H.264, MPEG2, and VC-1 content. More technicalities here.
The Mini-Itx Motherboard of Choice - Zotac IONITX A-U
Mini-ITX is a 17 x 17 cm (or 6.7 x 6.7 inches) low-power motherboard form factor. These boards can often be passively cooled due to their low power consumption architecture, which makes them useful for home theater systems.
Several mini-itx motherboards support the ION platform, including ASUS AT3N7A-I and others. However, after another quick google search, I realized that the right choice here must be Zotac IONITX A-U, not only because they were the first to build the mini-itx ION, but mainly because they have a superior product, with the following advantages over the ASUS:
1. External DC power supply. One of Zotac's mini-itx ION models comes with a unique DC power supply. The board has no ATX power supply connector on it, instead it relies on an external 90W power brick similar to what you’d get with a notebook. This was very important for my purposes as I intended to use no case for the HTPC and hence no ATX power supply.
2. Integrated WiFi. The Zotac board has on-board WiFi, while ASUS’ board has on-board Bluetooth. For my purposes, the WiFi is by far more important.
3. Passive cooling. The Zotac board has a huge heatsink and passive cooling is fully supported. The ASUS board, on the other hand, does not support passive cooling and instead has a cooling fan that spins at nearly 6000RPM. This is noisy.
Why Caseless?
At first I thought I'll use one of the Mini-ITX cases available on the market. It's a small and quite neat black box which most living rooms can probably live with. A no-brand case with a PSU (200W) costs around $65. Then I thought, why bother? A case with a PSU comes with a noisy fan, and it adds costs really for nothing. On the other hand, a tiny caseless HTPC can be a cool object in the living room, much more than another black box.
Putting it all together
Finally, i built it up. I used some pieces of transparent perspex to cover the board, except for the giant heatsink which was left to happily live in the open air.
I placed a 2.5 inches SATA 160GB hard drive on top of the perspex (Western Digital Scorpio). Windows 7 was installed on the hard drive prior to connecting it to the board.
A 2GB DDR2 Kingston ValueRAM module was placed.
Cables were plugged: DC power supply, HDMI and even SPDIF optical fiber cable was connected to the Home Theater receiver (just because it's possible...).
Now I needed a switch to turn the HTPC On and Off, a functionality normally provided by the case. For this purpose I used a switch with some leds I took from an old PC case.
I also spent some time wondering what would be the best way to control this tiny creature, and I tested some IPhone apps developed for this purpose. Eventually I gave it up and purchased a real keyboard: X-Gene 2.4GHz Wireless Mini Keyboard with 800 DPI optical trackball and 15 meters effective working range. This is more than enough.
That's it. The ION is now placed in the living room on top of an XBOX360 unit. The pictures demonstrate.
