RV770: AMD ATI Radeon HD 4870 - RV770: Other Features

By Edward Chester



  • Editors choice
RV770: AMD ATI Radeon HD 4870


Our Score:


One of the headline features of R600 was its 512-bit wide ring-bus memory controller. This gave unprecedented memory bandwidth and was something ATI was very proud of at the time. However, it was a very silicon-expensive design that didn't use its resources very efficiently. So, for RV770, ATI has gone back to the drawing board and come up with a completely new (though actually fairly conventional) memory controller design.

A central hub allows memory to be accessed from any part of the chip but the actual controllers have been moved to the edge of the chip where they're next to the most memory-bandwidth hungry parts. For low memory usage parts like the CrossfireX interconnect and UVD2 controllers, memory access is handled directly by the hub. By combining this new configuration with the latest GDDR5 memory (at least for the HD 4870) ATI has reduced latency and increased bandwidth to a colossal 192GB/s - nearly twice that of R600.

Another key change in RV770 is the improved AA performance. ATI went back to the drawing board when designing the ROPs and in particular greatly increased dedicated AA hardware. On R600 and RV670, dedicated AA hardware was poor and AA more often than not was performed using the shaders, which had a massive impact on performance.

Energy efficiency has also been improved thanks to clock gating that reduces the clock frequency of the card when not gaming or doing intensive GPGPU work. It would seem these improvements work, as well...

Finally, let's finish our look at the features of RV770 with another one of those lovely overlaid die shots. As with the similiar shot we looked at of GT200, the unmarked section (in this instance coloured in orange) will be a miscellany of other control logic like the thread scheduler and raster setup.

Varis Vitols

July 5, 2008, 2:51 pm

Yeah, it was about time!

Matthew Bunton

July 5, 2008, 5:43 pm

This is the best bang for buck right now, good to see the ATI cards fighting back. Though it is still too early to upgrade in my opinion.


July 6, 2008, 1:18 am

if ati get cuda... i will get this card from sapphire(it have 2 (4 pin to 6 pin conector)(my power suply just have one 6 pin conector) but only if it get cuda, because i like to play games but i also do some video editing and transcoding videos to my zune and it take like 4hrs to covert a dvd to h.264 in my conroe


July 6, 2008, 2:10 am

Your comment on the CoD4 results is incorrect. The HD 4870 beats the GTX 280 comfortably.

It simply fails to be the double card GX2.

Varis Vitols

July 6, 2008, 3:58 am

It depends on what u upgrade from...


July 6, 2008, 6:14 am

Probably not worth upgrading from a 8800GT to a 4850 but the 4870 looks like it could be a possibility. Hopefully ATi will have OpenCL to compete against CUDA but I'm not bothered by the lack of support for it.


July 7, 2008, 3:35 pm

anybody know the minimum power supply rating? looking to install in Dual-Xeon Dell workstation with 700w PSU??


July 7, 2008, 4:06 pm

My X1950XTX is looking a bit long in the tooth now. Getting that itchy upgrade feeling.


July 7, 2008, 9:08 pm


I wouldn't look at it like that, it completely depends on what else you're running in your system. At peak the card will draw 150 - 200W, if you've got that much headroom in your current supply then you'll be fine. Otherwise you may need to upgrade. Easy way to check is with a plug-in power consumption meter. They're only about 㿀.

What card are you upgrading from?


July 8, 2008, 12:18 am

Hmmm, thanks ED. The Dell manual's state GPU's upto 150W(supported) so I may be pushing it if you say it draws upto 200W. Upgrading Dell PSU's I don't think is that easy as your probably aware most components are besopke (got to love Dell).


July 8, 2008, 1:09 pm

Ah, that could be a bit of a problem. Dells are an absolute pig to work with.


July 14, 2008, 5:22 pm

^^ wrt the Dell PSU prob - not sure about the Xeon's, some of the midi-tower cases still have the same footprint as a regular PSU, but just proprietary gaps for the kettle lead... in which case you can buy a normal PSU and get out the metal cutters and drill... I've got "creative" with a few Optiplex's over the years... :o)


July 14, 2008, 5:24 pm

and thanks for the great review!!

As per DMN's comment, that X1950XTX-GDDR4 (me too!) is suddenly looking really long in the tooth :o)))


February 15, 2009, 7:58 pm

i have got to get me one of these...

Joseph Middleton

August 24, 2009, 3:43 pm

This Radeon 4870 by HIS... It's not mentioned how much on board memory it has...

512MB or 1GB?

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