ATI launches new HD 4000 series at sub-$100 prices

ATI's HD 4850 and HD 4870 have proved themselves tremendous successes in the market, but up until today, there's been no next-generation ATI GPU for buyers wanting a card under the $100 mark. Today, that changes with the launch of the ATI HD 4670 and 4650, priced at $79 and $69, respectively. Certain enthusiasts might sneer at the idea of spending so little on a graphics card, but ATI and NVIDIA sell a tremendous number of cards in the sub-$100 range, and depend on it as a major source of revenue. HangZhou Night Net

Performance and market positioning

Unfortunately, ATI's sample card didn't arrive until yesterday, and 24 hours is too short a time for a proper performance examination. We'll be discussing card performance over on Kit, starting tomorrow,where I'll examine performance in 3DMark: Vantage (I'm curious to see how the 4670 compares to the 3850 in certain feature tests), Call of Duty 4, and World of WarCraft. Past that point, I'll be taking suggestions on what benchmarks and results readers would like to see; plan to weigh in if you have preferences.

Up until now, ATI has depended on the HD 3000 series as a budget line; HD 3450s start around $29, the first HD 3650 pops up at $58.99, and the HD 3850 is $99.99 ($74.99 w/rebate). If the HD 3000 series had been a strong product line this would be no problem, but such is not the case. The HD 3850 and 3870 were hailed at launch as offering an excellent price/performance ratio, but ultimately failed to have much staying power against NVIDIA's 8800 GT/9600 GT onslaught. The HD 4650 and 4670 should offer NVIDIA a new challenge on several fronts.

Please to be forgiving of the dithering—that's ATI's slide, not my mad PowerPoint skillz

Both cards are designed to draw less than 75W of power (59W for the 4670, 48W for the 4650), meaning neither requires an additional power cable. ATI also states that it targeted systems with 400W PSUs, anyone with a power supply in that range should have no problems with the card. Of course, given how conservative such estimates are, it wouldn't suprise me if the card was stable on a 350W or 300W PSU, though I wouldn't exactly recommend it.

New features for budget cards, card comparisons

One welcome change between the HD 4600 and HD 3850 is ATI's fixed antialiasing (AA) implementation. In most video cards, the resolve step is handled by the raster operator partitions (ROP) or render back-ends if you prefer ATI's term. According to the company, AA was actually broken in both the HD 2000 and HD 3000 series, and couldn't be implemented in the traditional manner. ATI solved the problem by performing the necessary resolve in the shaders instead, and while this allowed for some interesting AA options (wide-tent filter, narrow-tent filter), it also had a heavy impact on performance.

The good news is, that issue is gone in the HD 4000 series and these new cards extend that fix into the budget market. RV730 XT is a cut-down implementation of the original RV770, but the ROP units that the card does carry are still more powerful than what appeared on the HD 3850, and are capable of outputting significantly more pixels per clock.

CardGPUNo. stream processorCore clock
MHzPixel fillrate
GT/sMemory clock
MHzBus widthMemory bandwidth
GBpsATI HD 4670RV730 XT320750122000/1800128-bit32AT HD 4650RV730 XT320750121000128-bit16ATI HD 3850RV67032068010.7830256-bit53.1NVIDIA 9600/8800 GS(O)G92965506.6800192-bit19.2NVIDIA 9600 GTG946465010.4900256-bit57.6

The chart above gives specs on the new HD 4000 cards, the older HD 3850, and both the NVIDIA 9600/8800 GS(O) and the 9600 GT. I can't help but snark just a little at NVIDIA's "new" 9600 GSO, given that it's literally nothing more than a rebranded 8800 GS. I've defended NVIDIA's decision to launch a "GeForce 9" series in the past, but that was back when the higher-end cards were debuting with new features (think hardware VC-1/H.264 decoding), or in previously unavailable configurations (9800 GX2). Last month's 9500 GT, however, was little more than an 8600 GT with higher clockspeeds and a 65nm processor. NVIDIA's also pulled this trick with the 8800 GT; the 9800 GT "refresh" is the exact same part at the same clockspeeds.

The HD 3850 and HD 4600 cards all carry 320 stream processors, but the new 4000 series parts are based on a newer GPU, and as such, will benefit from whatever secret sauce AMD baked into the original RV770 chip. Fill rate is up slightly compared to the 3850, but memory bandwidth is significantly lower; the 4670 has just 60 percent of the 3850's bandwidth, while the HD 4650 drops to 30 percent. This reduction comes courtesy of the 128-bit memory interface on both cards; the 4600's higher RAM clock isn't nearly high enough to compensate. ATI has promised that the 4670 should at least equal the 3850s performance, and both of the newer cards do carry 512MB of RAM standard, compared to the 3850's 256MB.

The 9600 GT and the 9600 GSO are more different than their names suggest. The 9600 GSO is built on the G92, but two of its texture processing clusters (TPCs) are disabled.. The 8800 GT that first introduced to G92 had just seven of its eight TPCs enabled; the 9600 GSO is what you get when you shut down another cluster.

Once you understand that, the rest falls into place. With two of its TPCs shut down, the GSO loses access to its fourth raster operator partition and the fourth memory channel that attached to it. The card is capable of outputting 12 pixels per second for a peak fillrate of 6.6Gpixels—the smallest of the cards on this list.

In contrast, the 9600 GT is built on the G94's more balanced design. The GT has just 64 stream processors compared to the GSO's 96, but NVIDIA appears to have preserved both the card's fourth ROP and its 256-bit memory bus. The 9600 GT's higher price ($94 and up at Newegg) still puts it in the running against the $79 4670, and the G94-based card has been a strong offering for quite some time. If ATI manages to unseat it with a cheaper part, it'll be quite the coup.

Concerning AGP

I asked ATI if they were finished with the AGP interface, and the company immediately responded that no, they would continue to support AGP users. ATI has provided board manufacturers with the necessary information to build AGP cards, and expects to see 4670s in that flavor in the future. There are no plans to bring the 4800 series to market on the older interface, but the current high-end AGP cards top out with the Radeon 3850. The 4670 should outperform that card, and provide a reasonable upgrade path.

I also broached the question of whether or not we'd see PCI or PCIe x1 cards from ATI, and met with a considerably cooler response. ATI's perception of the situation is that demand for cards on these interfaces is extremely limited, and while I generally agree, I noted that Intel's Atom desktop boards are currently PCI-only. The company said it would consider backing these interfaces, so if you'd like to see cards, drop me a line or comment in the forums.

Further reading:Anandtech: "AMD Radeon HD 4670: Ruling from Top to Bottom"

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