Hands on: High def, low power

Smooth playback of high-definition (HD) video presents a considerable challenge for even respectable PCs, but it’s a situation we’ve seen before.

Only a few years ago, DVD playback brought most PCs to a standstill. The solution then ­ as now ­ was to employ specialist help to relieve the strain on the main processor.

Decoding DVD’s Mpeg2 format has long been accelerated by graphics cards, and most graphic processor units (GPUs) now offer a boost to decoding the formats used for HD. But simply fitting a card with a GPU may not guarantee smooth HD playback.

If you’re coupling them with anything less than a respectable dual-core processor, you could still find your system maxed-out at 100 per cent and dropping frames. Indeed, our test media PC, which uses a mobile Core Duo T2600 processor, failed to smoothly decode the toughest Blu-ray titles, even when fitted with graphics cards featuring Ati X1600 or Nvidia 7300 GS GPUs ­ both of which sport H.264 acceleration.

At times like these you simply need more processing muscle, and there are two routes you can take: one is to upgrade the main processor; the second route is to try more effective acceleration from the GPU.

Nvidia claims its latest Geforce 8500 and 8600 desktop GPUs, along with the Geforce 8400M and 8600M mobile GPUs, are the first to offload 100 per cent of Blu-ray and HD DVD H.264 video decoding from the main processor. Let’s see if they really can relieve the strain from our T2600.

Test system
Our test system consisted of an Intel Core Duo T2600 Mobile processor, fitted in an Asus N4L VM DH motherboard with 1GB of Crucial DDR-2 memory. To test Nvidia’s claims we fitted a Gigabyte GV-NX86S256H card, which uses a Geforce 8600 GPU. This full-height PCI Express card features a massive heatsink for silent cooling, dual-link DVI ports and 256MB of GDDR3 memory.

We measured the processor hit when playing scenes from Casino Royale and X-Men III on Blu-ray using Power DVD Ultra at a resolution of 1,920x1,080 pixels and compared the performance of the Gigabyte card against the Sapphire X1600PRO HDMI, which employs an Ati X1600 GPU.