Radeon HD5770 Detailed Features

The main attraction of ATI's new line of video cards is the brand new GPU with its 40nm transistors and an improved architecture. The chip in the 5700 series is called "Juniper" and is essentially half of the "Cypress", the high-end chip in the HD5800 series that was introduced in September, 2009.

The Juniper die is very small, as can be seen with this comparison to a well known dimensional standard. ATI still managed to cram over a billion transistors on there, and the small size is critical to the pricing strategy that ATI is pursuing with these new releases.

1 GB of GDDR5 memory, on a 128-bit bus with a 4.8 Gbps memory interface offers a maximum memory bandwidth of up to 76.8 GB/sec. Cutting the Cypress GPU in half limited the bus to 128-bit, but ATI has bumped up the clock rate on all their new boards. With GDDR5 running at 1200 MHz, don't expect memory to be a bottleneck on this card. There is some limited room for memory overclocking, all sanctioned by corporate, via the Overdrive tool distributed by AMD.

The H5GQ1H24AFR-T2C chip from Hynix is rated for 5.0 Gbps, and is one of the higher rated chips in the series, as you can see in the table below. An overclock to the 1250-1300 MHz range is not unthinkable, especially if utilities become available to modify memory voltage.

The power section provides 3-phase power to the GPU; that's about average for a mid-range graphics card, and while increasing the number of power phases achieves better voltage regulation, improves efficiency, and reduces heat, ATI has used the inherently lower power requirements of the Juniper GPU and some fancy footwork in the power supply control chip to reduce power draw to very low levels. Where the HD5800 series used a number of Volterra regulators and controllers, the HD5770 makes do with one L6788A controller chip from ST. It's still a relatively sophisticated controller, and the combination of a lower power GPU, low power GDDR5 memory, and smart power supply design yields an incredibly low power consumption of 18W at idle and 108W under duress. ATI benchmarked these chips with 3DMark03, which they claim pulls higher current than more current versions of the synthetic benchmark.

We've already looked at the back side of the board, and I promised a surprise. Well, when is the last time you saw a DIP switch on a discrete graphics card? I can't remember if I've ever seen one. The Radeon HD5770 has five dual-switch modules mounted on the PCB and they're not labeled, except by their component designator, SW400x. They are covered with tiny pieces of Kapton tape, so they don't stand out quite as much as if they were bare, but after a second glance I knew they couldn't be anything else. I don't know what they are for, so let the conspiracy theorizing begin. While we're at it, it's interesting to note that the switches don't appear on production units, just solder links, where required.

The assembly quality on the PCB was not the best I've seen, but I had engineering samples to look at. Once we have some ATI partner cards in house, we'll take another look. Now, let's dive into the testing portion of the review, where there are a few surprises waiting.

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