______________6. Graphics Card¯¯¯¯¯¯¯¯¯¯¯¯¯¯_____________Selection Guide¯¯¯¯¯¯¯¯¯¯¯¯¯
The most important criteria for choosing a video card for HTPC are:
- Hardware assist for decoding HD contents (of all three formats MPEG-2, H.264, and VC-1)
- HDCP (High-bandwidth Digital Content Protection) support
- Picture quality
How about HDMI? HDMI (High-Definition Multimedia Interface) is an high-definition digital audio/video interface that is replacing analog audio/video and older digital standards such as DVI and has become the de facto standard interface in the consumer electronics market. HDMI 1.0/1.1/1.2 provides 4.9 Gb/s
bandwidth and the current HDMI 1.3 provides 10.2 Gb/s
that has enough headroom for 1080p at 60Hz and 8 channel/24 bits/192 kHz LPCM audio
(e.g. sounds decoded from the new digital audio codecs Dolby TrueHD
and DTS-HD Master Audio
) as the following simple calculation shows:
- 1920 x 1080 pixels x 60 Hz / 0.95 (5% overhead) = 131 MHz (megapixel/s), 131 MHz x 24 bits = 3.14 Gb/s
- 24 bits x 192 kHz x 8 channel = 36.9 Mb/s
HDMI video is compatible with the existing digital standard DVI and in fact one form can be converted to the other via a simple adapter. So there is nothing new. In contrast HDMI audio completely takes over the aged digital standard S/PDIF which supports only stereo PCM
and 5.1 Dolby Digital/DTS
with the maximum bandwidth around 12 Mb/s.
Unfortunately HDMI audio has not been realized yet in the PC world and we are still confined to S/PDIF. As a matter of facts, every HDMI video card simply passes S/PDIF signals from a sound card or onboard audio codec over the HDMI connector. Thus there is no real advantage of the current HDMI solution over the existing DVI + S/PDIF solution
. Recent IGPs (ATI Radeon Xpress 1250 for Intel and AMD 690G) are no exception. Right now the only way to take the full-rate lossless multichannel sounds from the PC is use analog outputs
The upcoming ATI HD 2000 series GPU has a built-in audio controller that makes it possible to grab audio outputs directly through the PCI Express bus, but the audio quality is still at the level of S/PDIF. The following figure shows the ideal HDMI audio solution we are waiting for that transmits lossless full-bitrate multichannel PCM audio streams.
___________NVIDIA Cards¯¯¯¯¯¯¯¯¯¯¯PureVideo HD
NVIDIA's second generation PureVideo HD
engine provides 100% offload
for H.264 decoding. That means that any decent PC with a video card with this engine can play back HD contents smoothly. The new engine consists of
- VP2 (the new Video Processor)
- H.264 BSP (Bitstream Processor)
- AES-128 Decryption Engine (AES = Advanced Encryption Standard)
The first two engines accelerate the four major steps of the decode process for MPEG-2, VC-1, and H.264:
- bitstream processing (reverse entropy) (by H.264 BSP; only for H.264)
- inverse transform (by VP2)
- motion compensation (by VP2)
- deblocking (by VP2)
and the AES-128 Decryption engine accelerates the decode of the AES-128 encryption protocol. Among them offloading the bitstream process in the H.264 decode process dramatically reduces the CPU usage.
However there is no big difference in the CPU usage in decoding VC-1
between the original PureVideo HD engine and the reworked PureVideo HD engine as the bitstream processor is not for VC-1.
This is the video part. None of the NVIDIA cards is able to transmit 7.1 LPCM audio through its HDMI connector.Cards
The second generation PureVideo HD is implemented in GeForce 8600 and 8500 series GPUs, but right now supported only under for Windows Vista. PureVideo HD support for the 8500 and 8600 GPUs under Windows XP is expected in June 2007. Here are brief specs:
- NVIDIA GeForce 8600 GTS (codenamed G84-400)
- Specs: Core/Mem: 675/2000 MHz, gDDR3 256MB, transistor count 289 million. Dual dual-link DVI + HDTV. HDMI can also be supported at the board manufacturer's discretion (none exists so far). HDCP support (by mandate from NVIDIA). DirectX 10. Power consumption: 47.0 W (peak 3D), 30.7 W (peak 2D), 21.4 W (idle)
- Notes: All the GTS cards follow the reference PCB design and most of them use the reference cooler. Therefore the only differences between these cards are core/memory clock, bundled accessories and aftermarket service.
- NVIDIA GeForce 8600 GT (codenamed G84-300)
- Specs: Core/Mem: 540/1400 MHz, gDDR3 256MB, transistor count 289 million. Dual dual-link DVI + HDTV. HDMI can also be supported at the board manufacturer's discretion (none exists so far). HDCP support is optional. DirectX 10.
- Notes: As the codename and the specs indicate, the 8600 GTS and the 8600 GT are physically the same except the clock speeds. However the reference cooler of the 8600 GTS is better than that of a 8600 GT card. Both 8600 GTS and 8600 GT top out at around core/mem: 760/2400 MHz. If you are interested in extreme overclocking, read NVIDIA 8600GTS Overclocking!.
- NVIDIA GeForce 8500 GT (codenamed G86-300)
- Specs: Core/Mem: 450/800 MHz, DDR2 256MB/512MB, transistor count 210 million. VGA + dual-link DVI + HDTV. HDCP support is optional. DirectX 10
You can see a complete list of GeForce 8600 and 8500 Series video cards in Appendix IV. Including it here is almost useless because every card is identical with the reference card! And almost all NVIDIA cards seem to be built by one company, Flextronics in China. Companies like BFG Tech, EVGA, and XFX are simply putting their own stickers and maybe cooling on the card then tweaking the BIOS with their own overclock settings (Hard|OCP
So which GPU should you choose? As for HD contents playback, there is not much difference between 8600 GTS, 8600GT and 8500 GT as seen in the HARDSPELL article DX10 is universalizing: G86/G84 complete test!
. Unfortunately there are only a couple of 8600 GT / 8500 GT cards that support HDCP. There are noticeable differences between them for gaming, however. My picks are:
________ATI Cards¯¯¯¯¯¯¯¯Avivo HD Technology
- eVGA GeForce 8600GTS Superclocked 256MB 256-P2-N765-AR
- Spec: Core/Mem: 720/2100, the reference cooler
- Price: ~$200
- Notes: This is the best combination of clock speed, bundled accessories, warranty and price. You can save $20 by choosing the standard clock version eVGA GeForce 8600GTS 256MB 256-P2-N761-AR (overclocking it is easy).
- ASUS EN8600GTS SILENT/HTDP/256M
- Specs: Core/Mem: 675/2000, passive cooling, occupies two slots.
- Price: ~$200
- GIGABYTE GV-NX86S256H
- Specs: Core/Mem: 675/2000, passive cooling, occupies two slots.
- Price: ~$197
- PNY Verto 8600 GT 256MB PCIe VCG8600GXPB
- Spec: Core/Mem: 540/1400, the reference cooler
- Price: ~$150
- ASUS EN8600GT SILENT/HTDP/256M
- Spec: Core/Mem: 540/1400, passive cooling, occupies two slots.
- Price: ~$143
- Notes: If you prefer 8600 GT with a passive cooling, this is it.
- GIGABYTE GeForce 8500 GT GV-NX85T256H
- Spec: Core/Mem: 500/800, passive cooling
- Price: ~$100
- Notes: This is one of the few 8500 GT cards that support HDCP. If you don't care of gaming performance, this is the best bang for your buck.
ATI's new Avivo HD Technology
, the successor to the Avivo Technology, integrates two new engines:
- Universal Video Decoder (UVD)
- Advanced Video Processor (AVP)
The UVD features more or less the same functions as NVIDIA's PureVideo HD: offloading
- bitstream processing/entropy decode
- frequency transform
- pixel prediction
from the CPU, but in both VC-1 and H.264 codecs
. (The old Avivo Visual Processing Unit, VPU, lacks the bitstream processing capability, just like the first generation PureVideo HD.) On the other hand the AVP allows the GPU to apply hardware acceleration and video processing functions while keeping power consumption low.
Another striking feature of the new ATI cards is a built-in audio controller
that grabs audio output through the PCI Express bus and transmits it through HDMI. Unfortunately it supports only Dolby Digital 5.1, DTS and 32kHz, 44.1kHz, 48kHz/16-bit PCM stereo
. Although it is a step forward toward the true HDMI audio, practically there is no advantage over the current S/PDIF passthrough solution.Cards
Originally ATI planned to implement the UVD in X1xxx series GPU, but it did not happen. The upcoming ATI Radeon HD 2600/2400
GPUs (to be released in July 2007) integrate the Avivo HD Technology:
Note that the high-end model Radeon HD 2900 XT lacks UVD.
The upcoming IGP (Q1 2008)
will also support DirectX 10 and the Avivo HD Technology.ReferencesVideo PlaybackHDMIGeForce 8600 and 8500 Series Reviews
Radeon HD 2000 Series ReviewsHQV
- AnandTech – DX10 for the Masses: NVIDIA 8600 and 8500 Series Launch (April 17, 2007)
- AnandTech – 8600 GT/GTS Follow-up Performance (April 24, 2007)
- AnandTech – NVIDIA GeForce 8600: Full H.264 Decode Acceleration (April 27, 2007)
- bit-tech.net – NVIDIA GeForce 8600 GTS (April 17, 2007)
- Guru of 3D – GeForce 8600 GT and GTS review and Shootout (BFG GeForce 8600 GTS OC, GALAXY GeForce 8600GTS, Point of View GeForce 8600 GTS EXO, XFX GeForce 8600 GT/GTS XXX) (April 17, 2007)
- HARDSPELL – DX10 is universalizing: G86/G84 complete test! (April 18, 2007)
- Hot Hardware – NVIDIA GeForce 8600 GTS and 8600 GT (April 17, 2007)
- nV News – NVIDIA GeForce 8600 GTS Preview (April 17, 2007)
- OCWorkBench – CeBIT 2007 : NVIDIA GeForce 8600GTS Photos Review (March 11, 2007)
- OCWorkBench – CeBIT 2007 : NVIDIA GeForce 8600GT Photos Review (March 11, 2007)
- OCWorkBench – Test Environment of NV 8600GTS benchmark (April 16, 2007)
- OCWorkBench – NVIDIA 8600GTS 3Dmark03 SLI Results (April 16, 2007)
- OCWorkBench – NVIDIA PureVideo HD on GeForce 8500 and 8600 series uses new Video processing engine (April 17, 2007)
- techPowerUp! – NVIDIA GeForce 8600 & 8500 Preview (April 17, 2007)
- Tom's Hardware – GeForce 8600: DirectX 10 For The Masses (April 17, 2007)
- VR-Zone – Mainstream Graphics Arena: The Launch of the GeForce 8600 and 8500 series (April 17, 2007)
- VR-Zone – NVIDIA 8600GTS Overclocking! (April 2, 2007)
- X-bit labs – GeForce 8 Streams to the Mainstream: Asus GeForce 8600 GTS Review (April 18, 2007)
- XTreview.com – 8600 GTS and 8600 GT Review and Benchmark (April 17, 2007)