Original Link: http://www.anandtech.com/show/1777

GeForce 7800 GT: XFX Overclocked

by Josh Venning on August 30, 2005 10:35 PM EST


Introduction

We've been looking at NVIDIA's 7800 GTX graphics cards lately, and the different vendor modifications have shown some impressive performance results. NVIDIA is still the reigning champion of graphics cards right now, and has been since the release of the 7800 series. While the 7800 GTX has more than proven NVIDIA's capabilities, it's also managed to make gamers on a budget cringe when thinking about buying one. With the lowest 7800 GTXs at around $500, many PC owners are finding it very hard to justify owning one, no matter how powerful it is.

But now there's some good news. Aiming for another group of consumers, NVIDIA has decided to release a slightly less powerful (and less expensive) version of the G70: the 7800 GT. This could mean lower prices for potentially not-so-much-less performance, and we're very interested to see what these cards are capable of.

We've already looked at how the 7800 GT ranks alongside the GTX and other graphics cards, including dual-card SLI setups, and you can take a look at the review here. We've seen how, performance-wise, the 7800 GT falls in between the 7800 GTX and 6800 Ultra, and in these next reviews, we will be looking at the different 7800 GTs and comparing them much like we did with the 7800 GTXs. There will be some changes, however, with fewer reviews that will cover more than one card.

In this article, the first of the NVIDIA 7800 GT reviews, we'll be looking at the XFX GeForce 7800 GT Overclocked. As with the 7800 GTX, we will be doing a series of articles focusing on individual aspects of each of the different vendor cards that we can get a hold of, and comparing them to each other as time goes on. We'll be looking at performance, as well as power load, heat, and noise levels, and also how the different cards overclock. As always, price will be one of the biggest factors in how these cards compare, and we'll be keeping you updated on price trends as we review each card.



The Card

We've talked a little about this before, but the 7800 GT is nearly identical to the 7800 GTX aside from a few things, the most important being the pipelines. The GT drops 1 vertex and 4 pixel pipelines, getting about 17% less pixel power per clock cycle than the GTX. This means that even at the same clock speed, the GTX should have a theoretical advantage of about 20% over the GT. Another difference is that the GT is clocked lower than the GTX: 400MHz core and 1GHz memory as opposed to 430MHz and 1.2GHz. However, as we will show in the next section, the clock speeds of the two cards are close enough together to overclock the GT up to or beyond the speed of the standard GeForce 7800 GTX.

That being said, the XFX GeForce 7800 GT Overclocked (in case it isn't obvious by the name) does come with a factory overclock of 450MHz core and 1.05GHz memory clock speeds. This will give it a slight increase in performance over the reference 7800 GT, and we'll be seeing by how much a little later in the review. Also, the XFX 7800 GT has dual link DVI on one port, just like the GTX, in case you are lucky enough to own a monitor that can use it.

As you can see, the XFX 7800 GT looks very similar to the XFX 7800 GTX, the only difference being the style of the heat sink. XFX has dropped the shiny rainbow sticker that was on the 7800 GTX and replaced it with a much more practical looking gray cutout; perhaps a reference to a “no frills” take of the 7800. The box is practically identical to the one for the GTX, complete with the unique “x” shape and extremely-difficult-to-open-without-tearing packaging.

Also, the card comes bundled with a few games: FarCry, X2 The Threat, and Moto GP2. We aren't sure about the other two games, but FarCry is a great game with graphics that will make you happy that you bought a 7800 to run it on. Next, we'll take a look at overclocking the 7800 GT.



Overclocking

As with the 7800 GTX, how the 7800 GT overclocks (beyond the factory clock) is something that we'll be looking at closely. Many of the 7800 GTXs had impressive factory overclocks, and the GT series looks to be no different. As we mentioned before, the XFX GeForce 7800 GT comes out of the box with a factory overclock of 450MHz core and 1.2GHz memory clocks. We were curious to know if we would be seeing the same core clock scaling that we saw with the GTX; specifically, if the performance increases were between the same frequencies.

Just to review, here is a brief explanation of what we saw happening with the 7800 GTX when adjusting clock speeds. Basically, we were seeing plateaus where consecutive core clock speeds had barely any impact on framerates (only a few tenths of a frame per second), then intermittent jumps up in performance between frequencies (i.e. between 472MHz and 473MHz). And because you get increasingly longer "plateaus" of minimal increase as you raise clock speeds, we've shown that this can cause for some confusion about how much faster each of the vendors' factory- overclocked 7800's really are.

After running some tests with Splinter Cell: Chaos Theory, we found that the frequencies didn't match up with what we saw with the 7800 GTX. We didn't see any jump in framerate between 472MHz/473MHz as we did with the GTX; instead, jumps occurred between 461MHz/462MHz and 477MHz/478MHz. We will be looking into this more closely in the next 7800 GT article, and hopefully, we can shed some more light on NVIDIA's frequency selection issues.

Interestingly, while attempting to overclock this card (the XFX GeForce 7800 GT), we managed to reach a core clock speed of 477MHz, which is actually a higher core speed than both the reference 7800 GTX (430MHz) and even some of the factory overclocked 7800 GTX's that we tested. This is equivalent to the performance that we would have seen at a 462MHz overclock. We did this without any special cooling systems, and the overclocking potential of these cards could be yet one more reason to choose the GT over the GTX right now. Buying a cheaper card and squeezing more performance out of it is maybe a better option than spending the extra money. But we have to say, as always, overclocking is risky and varies between cards, so if you plan on doing some overclocking yourself, we recommend paying very close attention to the warranty offered by the manufacturer.



Performance Tests

We ran benchmarks on the 7800 GT with the same system that we used for the 7800 GTX tests:

MSI K8N Neo4 Platinum/SLI motherboard

AMD Athlon 64 FX-55 Processor
1 GB OCZ 2:2:2:6 DDR400 RAM
Seagate 7200.7 120 GB Hard Drive
OCZ 600 W PowerStream Power Supply

We'll also be testing the card's performance in the three games that we've been using: Battlefield 2, Doom 3, and Halflife 2. We'll be testing all three games at 1600x1200 with and without AA. We chose this as our resolution because it reflects what is most used by people who get a 7800 GT, given that most cost-effective LCD monitors still don't support resolutions much higher than this.

Since this is our first 7800 GT article, and we don't have any other versions to compare the XFX 7800 GT with yet, we'll be looking at how the GT compares to the 7800 GTX reference card. Because we were able to overclock our XFX 7800 GT a little bit higher than the reference 7800 GTX, we can see how significant it is to have one more vertex and 4 more pixel pipelines.

Battlefield 2 Performance

Battlefield 2 Performance

Doom 3 Performance

Doom 3 Performance

Half-Life 2 Performance

Half Life 2 Performance

As the numbers show, the reference 7800 GT framerates are quite a bit lower than the 7800 GTX, particularly with Battlefield 2. This is because Bf2 is a fairly new game and it places a higher stress on the graphics card at 1600x1200 than the other two games. In Bf2, there's about a 20% decrease in fps between the reference 7800 GT and GTX both with and without AA enabled. Doom 3 and Halflife 2 saw a 14% and 18% decrease in fps respectively with AA enabled, but there wasn't nearly as much of a drop in those two games with no AA.

When we tested the XFX GeForce 7800 GT Overclocked, we found the numbers to be much closer to those of the 7800 GTX. On the 7800 GT, BF2 still has about a 10% decrease in fps from the GTX, which might be noticeable during game play. But the other differences were small enough not to make much difference.

As you can see when we overclocked our 7800 GT to 462MHz and 1.2GHz, we managed to match and even slightly surpass (in Doom 3) the framerates of the GTX. This is significant, but we aren't quite sure if we'll be able to see the same results on other 7800 GTs. These numbers really show us how there isn't a very big difference at all in G70 performance with one less vertex and four less pixel pipelines at 1600x1200 and lower; all the more reason to save $100 and go with the GT if a very large expensive LCD isn't in your computer room or within your budget.



Power, Heat & Noise

Power

Load Power

Considering how power-hungry some of the GTXs were, we were curious to know how this would look on the 7800 GT. As we've found with the 7800 GTXs, there's a lot of variation in heat and power load between the different vendor cards, and the same will likely be true here. As the chart shows, the 7800 GT doesn't create nearly the same kind of power draw that the different GTXs do. We get a draw of 231 W running stress tests at the factory-clock speed of 450MHz, and 235 W when overclocked. While this is lower than the GTX, unfortunately, it's not low enough to let you skimp on your power supply.

For reference, the system load was 125 W while idle. This is about 20 W lower than idle under the GTX.

Heat

Load Temperature

We found that this 7800 GT ran considerably cooler than the GTX, and we're curious to see if this will be similar with other 7800 GTs. The load temperature of a card can be important because of the part that it plays in overclocking. It's also something to consider if you live in very hot climates or have small computer cases with poor circulation. With a temperature of 60 degrees C at 450MHz and 61 degrees C at 462MHz, this card handles heat pretty well. We'll see if XFX is unique in this among other GT vendors, or if they all generally run this much cooler than the GTX.

Noise

With the 7800 GTX, there didn't seem to be much of a correlation between higher clock speeds and noise levels as we might have guessed. One of the highest clocked GTXs, the EVGA e-Geforce 7800 GTX KO, was also the least noisy according to our numbers, but this is likely because of the metal fan casing, which encompassed the entire front of the card. We've found that with the GTX, the CPU fan is the predominant noise in the room when testing, which makes it practically impossible to try to distinguish differences in fan noise between the cards by ear.

Noise

Until now, that is. As it turns out, we were quite surprised by how loud this card proved to be. In fact, the card was so noisy when we started up the system that it effectively drowned out the CPU fan. While we weren't expecting the GT to get a noise level quite as loud as the GTX, our tests revealed a sound level of 54.7 for the GT, about two and a half times louder than any of the 7800 GTXs that we tested. This might well be a big negative for some people looking at this card, but keep in mind that hearing is subjective, and many people won't notice or mind the extra sound at all. Of course, we're very interested to see if this level of noise is common among the vendor 7800 GTs, and we'll have something to which to compare it for the next article. The higher noise levels could also play a large part in the significantly lower temperatures.



Final Words

While still not quite being what we would call a “mid-range” card, the 7800 GT comes a step closer to it. At about $390 (at the time that this article was written), the XFX 7800 GT puts a noticeably smaller strain on your wallet than the GTX. Meanwhile, it still provides comparable performance at decent resolutions. The lowest priced 7800 GTX that we could find was the MSI NX7800 GTX for about $480; almost $100 more than XFX's factory overclocked 7800 GT. Considering what we've seen in our performance tests, this is a pretty sweet deal, and we feel that those looking for a high end card would not be missing out by choosing the 7800 GT over the GTX.

Those who might still want the GTX over the GT are those who like playing at the highest resolutions possible (and have the monitors to do so) with AA enabled. The majority of gamers, however, will be more than pleased with how well this card handles at 1600x1200 with or without AA. We even found that when enabling ultra high quality in Doom 3 at 1600x1200, the game ran just as smoothly on the GT as on the GTX.

If you are on a tight budget though, it's a sad fact that this card is still quite a bit out of your reach. It will be hard for some to justify paying $400 on a graphics card, but if ever there was a reason to do so, then this is it. Coming in at the same price point that the 6800 GT occupied at its launch, the 7800 GT is quite a worthy replacement. Because of the great performance that we see with this card, we feel that it's worth the splurge if you can manage it, especially if you want to make newer games look good and run smoothly. We feel that this card (the XFX GeForce 7800 GT Overclocked) is also a particularly good deal at $390 because of the factory overclock, which puts it closer to the GTX in terms of performance.

We'll be looking at how the different 7800 GTs compare to each other as we review them, so be on the lookout for another 7800 GT article soon. We want to make these reviews as helpful as possible, so any comments or suggestions that you have regarding tests, cards, or anything else, please let us know.

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