ATI Radeon HD 5770
Not as powerful as we'd hoped, and a little costly but great for low resolution screens
Price £127 Manufacturer HIS GPU Clock 850MHz Unified Shaders 800 Memory 1GB GDDR5 1,200MHz Memory bus 128-bit Requires 450W PSU
The ATI Radeon HD 5770 and 5750 have been pruned considerably harder than the 5850 in order to cater for the most affordable end of the market.
Each offers half the number of shaders of the 5870 and 5850 respectively, and manages a 128-bit GDDR5 memory interface too.
It's almost as if AMD gleefully took to the 58xx series with a chainsaw – producing twice the number of chips from the same wafer. This has resulted in far more palatable price points, but the obvious question is how has this hit the raw performance of both cards?
Easily the most interesting of the two chips, the Radeon HD 5770 operates at the same 850MHz core and 1.2GHz memory clocks as the family's fastest offering, but don't forget that it packs only half the Unified Shaders and ROPs.
Chipping away
Unfortunately, the rules of semiconductor design mean that half a chip going quickly is a lot worse than a full one going slowly.
In other words the 5770 takes a comprehensive hit from its lack of semiconductors when compared to the 58xx chips. That said, the chip still boasts over one billion of those little transistors, putting it ahead of the outgoing 4870 by some 84 million.
So surely that means that it's going to pound that in any head-to-head comparison? In a word, no.
This is because a huge chunk of this extra silicon is to make room for the DirectX 11 features, which may pay dividends in the future, but right now it needs to produce decent performance at a decent price point.
The 128- bit memory interface means that it just doesn't have the throughput of the 4870, equating to performance that can be found lagging in that outgoing card.
The fact is that cards based on the 4870 are dropping in price on an almost daily basis, and it's difficult to get too excited about the Radeon HD 5770 despite the fact that in many respects it's a decent slither of silicon.
In a continuing theme, it's just a bit too expensive given what can be picked up for the same sort of money – the 4870 is a little cheaper, while the 4890 is only a little more expensive. Which leads naturally enough to the runt of the litter – the Radeon HD 5750. See benchmarks on the last page.
