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ATi MR 9700

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Unless you’re lucky enough to own one of the new generation of notebooks, you probably think of portable computing as being about convenience and compromise rather than a truly rewarding experience in its own right.

There can be no denying that even as recently as a couple of years ago, your average notebook tended to come equipped with a mediocre screen, truly appalling sound, low end processing power and graphics that might just power a quick game of Solitaire provided the wind was blowing in the right direction. Battery life was notoriously poor, prices were notoriously high and users tended to be stressed executives who simply had to work on the train to keep the company afloat. Owning a notebook wasn’t about choice, it was about necessity.

Today things are nowhere near so grim. Screens are now actually very good, even by desktop standards. Battery life is considerably better. Processors are nudging the top speeds available in your big beige box and at last, graphics capabilities are beginning to offer enough horsepower to run mainstream games titles.

The latest graphics chip from the ATi camp is the M11 core Mobility Radeon 9700 and is the subject of today’s review.

Being a mobile part it will be implemented at varying speeds anywhere between 390MHz and 450MHz depending on the particular manufacturer and/or notebook model and configuration. Likewise the memory may be run at varying frequencies dependant on stability and thermal considerations. In our particular instance the chip is strapped inside a GERICOM Hummer 30680 where it has been qualified to run with a core clock of 405MHz and a memory clock of 260MHz. We’ll not be reviewing the GERICOM notebook per se other than as a vehicle for the Mobility Radeon 9700 VPU, but as such it’s best if you know the kind of specifications it offers:

3.06GHz P4
512MB RAM
Intel 845G/PE chipset
Toshiba MK8025GAS HDD

Not dissimilar to the kind of specs you might find in a mid-high-end desktop PC. While we’re throwing specifications about, here is what the chip can lay claim to:

Offering up to a 30% MHz boost over its predecessor
Supports Microsoft® DirectX® 9.0
Pixel and Vertex Shaders
Quad rendering & dual vertex engines
Full precision floating point with full performance
0.13 micron VPU featuring Low-K process technology
Low power operation
Support for AGP 8X

Before we get on to the vastly more interesting graphics features let’s first look at one of the slightly less exciting but none-the-less vital technologies that has made such an advanced mobile die possible in the first place. The Mobility Radeon 9700 is the first notebook processor on the planet to feature low-k technology. The technology is quite complex so I’ll keep it as short and simple as I can.

The letter ”k” is used to represents the rather scary sounding “dielectric constant”, and a dielectric is, in simple terms, an electrical insulator. The lower the value of “k”, the better the material is as an insulator. This matters because as modern processors have continued to get smaller, so the pathways that carry the current around the inside of the chip have become crammed more and more tightly together, leading eventually to a situation where there’s simply not enough insulation between any two of the pathways to stop current leaking from one to the other; this is known as cross-talk. As a result of this, extra current needs to be supplied to counteract the losses which, of course leads to higher power requirements and greater heat generation, both serious considerations when power draw and heat are the curse of efficient notebook design. This is a rather simplistic explanation but what I’m saying is, shrinking a processor using traditional manufacturing processes generally leads to a more inefficient chip.

The obvious solution is to create these new, tiny 0.13µ cores using materials that offer greater insulation between the individual tracks, but implementing this seemingly simple idea into the already long-established chip making process and perfecting it to a level that yields enough “good” chips per wafer has been a long and weary process. As a rule, low-k materials tend to be fragile and porous which makes them particularly susceptible to damage from the etching and cleansing process needed in order to create the chip in the first place. TSMC, the foundry that makes the Mobility Radeon 9700 for ATi, uses Black Diamond, a silicon oxide based low-k CVD (Chemical Vapour Deposition) film from Applied Materials, and although early attempts were fairly disastrous it now claims that yields are up there alongside those of conventional FSG (Fluorine-doped Silicate Glass) processes.

The end result of all this grand sounding technology is a chip that packs a lot of very efficient circuitry onto a very small die and can be run using less power while also creating less heat.

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