Round up When AMD updated the RV670 chip used in the ATI Radeon HD 3000 series to the RV770 in the HD 4000 line, it went ballistic and increased the number of unified shaders from 320 to 800.

This change increased performance by a healthy amount and made the HD 4850 the apple of Register Hardware’s eye. But that was only the start of the story.

AMD's Radeon HD 4350: effectively one tenth of a...

The HD 3850 was a decent graphics card but the 320 shaders in the RV670 core didn’t give AMD much scope to conjure up a range of products based on the same chip. In effect, the HD 3650 was three-eighths of an HD 3850 and had the memory controller halved to 128 bits. The lowly HD 3450 was a mere one-eighth of an HD 3850 and only had 40 shaders and a 64-bit memory controller.

AMD didn’t have many options at the upper end of the scale as the difference between the HD 3850 and the HD 3870 was a simple matter of clock speed, and the increased power and heat of the HD 3870 required a hefty double-slot design. This left the range of HD 3000 products rather limited both in terms of performance and the spread of prices.

The RV770 chip changes the range of AMD graphics cards from top to bottom. At the high end, there's separation between the HD 4850 and the HD 4870 as the memory controller in RV770 includes support for GDDR 5, a new type of graphics memory that has double the bandwidth of GDDR 3. So 1GHz GDDR3 on an HD 4850 card has a 64GB/s bandwidth while the 900MHz GDDR 5 on HD 4870 has 115.2GB/s to work with.

...Radeon HD 4850

Add in a higher core speed and the HD 4870 has a handy edge over HD 4850, but it costs about £200 - a high premium when the HD 4850 typically costs £135.

If you’re in the market for a gaming graphics card then the HD 4850 and HD 4870 are strong contenders. But the fact of the matter is that most people don’t want to spend significantly more than £100 on a graphics card, and this is where things get interesting. All of the chips we’re covering today have the same features and support DirectX 10.1 as well as having a proper video core that's fully capable of handling HD movie playback without flogging your CPU to death. The interface is PCI Express 2.0 and the graphics card manufacturer can choose DVI, HDMI and DisplayPort connectors as it sees fit.

MSI's R4670: mixing and matching monitor ports

The differences between the models stem from the way that AMD has chosen to slice and dice the RV770 chip and its 800 unified shaders. Naturally, the width of the memory controller and the type of memory also play their part in performance. Similarly, the specification dictates the power draw, which, in turn, affects the amount of cooling on the graphics card.

We’ve already covered the HD 4850 and 4870 and their X2 variants at the top of the range, so we’ll start at the bottom of the range and work our way up from there. We tested all of the graphics cards on a 3.2GHz Intel Core i7 965 Extreme system built around an Asus P6T Deluxe motherboard, 3GB of Crucial PC3-8500 memory and a Western Digital 1TB Caviar Back hard drive running on 32-bit Windows Vista Ultimate Edition.

We would have liked to stick to the latest Catalyst 8.11 driver to keep the playing field level but we hit a snag. The latest Catalyst 8.11 driver is appropriate for every graphics card from the HD 3870 all the way back to the Radeon 9550, but things get horribly confused when you look at driver support for the HD 4000 series. The HD 4850 and HD 4870 have been around for some time and are properly supported by Catalyst 8.11 along with the HD 4670, but the HD 4830, 4650, 4550 and 4350 all require Catalyst 8.10.

There’s a further fly in the ointment as Catalyst 8.11 doesn’t support the Core i7 platform. How annoying. We can only hope that Catalyst 8.12 sorts everything out.

3DMark Vantage Results

Longer bars are better

3DMark06 Results

Longer bars are better

Radeon HD 4350 and HD 4550
The RV710 chip is one-tenth of the RV770, having just 80 unified shaders, a tiny 64-bit memory controller and an equally tiny power rating of 20W. For some reason, AMD has decided to call the DDR 2 version of RV710 the HD 4350, while the DDR3 version has been named the HD 4550. The 20W power rating means that both models have the option of passive cooling. However, the Sapphire HD 4550 that we tested is a compact card with a small active cooler. A small fan is usually a recipe for an annoying, buzzy design, but the Sapphire is amazingly quiet.

AMD's Radeon HD 4550: passively cooled

Although the gaming experience was nothing to write home about, we were pleasantly surprised that this £45 graphics card chugged through Far Cry 2 at 1280 x 1024 on Very High quality settings at an average of 15f/s. That’s not fast enough to play the game comfortably but it’s impressive that a budget card can make a decent fist of a modern game.

This is a proper graphics card with a 600MHz core and 512MB of DDR 3 that runs at 1800MHz. However, the 80 shaders restrict the performance to such an extent that it's really only of interest to the Media Centre brigade.

Radeon HD 4350
Reg Rating 75%
Price £35 Find the best online price

Radeon HD 4550
Reg Rating 70%
Price £45 Find the best online price

Radeon HD 4650 and HD 4670
The next step up is the RV730, which uses four chunks of the RV770 to deliver 320 unified shaders. The memory controller has been increased to 128-bit and once again there are two versions of the chip. The HD 4650 has a core speed of 600MHz and supports 512MB of DDR 2 memory with an effective speed of 1000MHz all wrapped up in a power requirement of 60W. The HD 4670 bumps the core speed to 750MHz in conjunction with 512MB or 1GB of GDDR 3 running at 2000MHz. These increases in clock speeds raise the power requirement to 75W so you’re effectively getting a Radeon 3850 that has been updated for 2008.

AMD's Radeon HD 4670: 320 unified shaders on board

It came as a major surprise that HD 4670 delivered lower performance than the HD 3850 across the board in our tests and the difference grew to silly proportions when we compared two HD 4670s in CrossFire with a pair of HD 3850s. We confidently predict that HD 4670 will blossom and flourish when AMD gets the drivers sorted but for the time being it's hard to see the appeal of the HD 4670 when the old HD 3850 does a better job.

Radeon HD 4650
Reg Rating 70%
Price £45 Find the best online price

Radeon HD 4670
Reg Rating 60%
Price £65 Find the best online price

Far Cry 2 Results
DirectX 9

Resolution 1280 x 1024
Very High Quality
Longer bars are better

DirectX 10

Resolution 1280 x 1024
Very High Quality
Longer bars are better

Far Cry 2 Results
DirectX 10

Resolution 1920 x 1080
Very High Quality
Longer bars are better

Power Draw Results

Power Draw in Watts (W)

Radeon HD 4830
The HD 4830 has 640 shaders with a core speed of 575MHz, and 512MB of 1800MHz GDDR 3 linked to a 256-bit memory controller. The reference design looks identical to a reference HD 4850 and the specification is so similar that both models have the same power figure, 110W, although the HD 4830 actually draws 15W-20W less than HD 4850.

In essence, the HD 4830 is four-fifths of the HD 4850 but it seems that AMD had last-minute thoughts about the specification of this model. Soon after review samples were sent out, there were emails galore stating that samples may have 560 shaders instead of the correct 640 and these emails were followed with Bios files to update the samples to the correct spec.

HIS' HD4830: a bargain to be had?

To add to our woes GPU-Z didn’t recognise the HD 4830 and merely described it as an HD 4800, so it was tricky to get a clear idea about the internal workings of the chip.

By the time we’d finished updating Bios, our reference design and samples from HIS and Sapphire were essentially identical apart from the coolers, package and price. The HIS is both quieter and cheaper than the Sapphire, but we prefer the appearance and cooling of the reference design.

The performance of the HD 4830 is impressive when compared to the HD 4850 - provided you use 3DMark as your test. In Far Cry 2 the gap opens up but once again this appears to be a question of driver performance, so we’re going out on a limb to say that HD 4830 is good now and will be very good by Christmas.

The pricing of HD 4830 is up in the air as it was clearly meant to be a £99 product, but the dollar exchange rate has pushed it up to £110. Hunt around and you may well find a HIS HD 4830 for less than £90, but we suspect it will be ‘while stocks last’.

Radeon HD 4830
Reg Rating 85%
Price £110 Find the best online price

More Graphics Chips and Cards...

Sapphire Radeon HD 4850 X2

AMD Fusion for Gaming

Sapphire 4850 Toxic

Nvidia GeForce GTX 280