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That big ol' chip
I was curious to see exactly how big this 80-million-transistor chip is, so I yanked the cooler off the GPU, only to find a big metal cap, or "heat spreader" if you wanna get fancy, on top of the chip. Like this:


The Parhelia-512 GPU is packaged in a metal heat spreader thingy So we can't tell exactly how big the chip is without probably ruining the card by pulling off the cap, and Matrox ain't saying. We do know it's fabbed by UMC on a 150nm process. I'm sticking with my estimate that it's a little bigger than Rhode Island. The metal cap is roughly the size of a former Soviet breakway republic, so I can't be far off.

The final specs
One thing we know now that we didn't before the card arrived is the final GPU and memory clock speed specifications. As we kind of expected, that hefty chip won't hit super-high clock speeds too well. The retail version of Parhelia comes in at only 220MHz, in fact, which is a little slow compared to the competition. The memory clock runs at 275MHz, or 550MHz in DDR-speak, which isn't fast enough to deliver the 20GB/s memory bandwidth Matrox initially intended. That's no big deal, though, because the GPU's clock speed is likely to be the limiting factor for performance in most situations.

There will also be an OEM or "bulk" version of Parhelia floating around out there in pre-built PCs and, most likely, at some mail-order houses. That version has a 200MHz GPU clock and 500MHz memory. The only way to tell the difference between the two cards for sure, according to Matrox, is a "B" in the model number of the bulk/OEM editions. So watch carefully. At least Matrox is being up-front about it, even though I'd prefer a better naming convention.

With that said, let's whip out the GPU table and see how the final Parhelia specs fit into the big picture. Remember, as always, that specs aren't destiny, and performance will vary. The chip table here is just a useful little guide to give you a sense of each chip's capabilities.

Core clock (MHz)Pixel pipelines Peak fill rate (Mpixels/s)Texture units per pixel pipelinePeak fill rate (Mtexels/s)Memory clock (MHz)Memory bus width (bits)Peak memory bandwidth (GB/s)
GeForce4 MX 4402702540210804001286.4
GeForce3 Ti 2001754700214004001286.4
GeForce4 Ti 4200 128MB25041000220004441287.1
Radeon 75002902580317404601287.4
GeForce3 Ti 5002404960219205001288.0
GeForce4 Ti 4200 64MB25041000220005001288.0
Radeon 8500LE25041000220005001288.0
GeForce4 Ti 4400 27541100222005501288.8
Radeon 850027541100222005501288.8
GeForce4 Ti 4600300412002240065012810.4
Parhelia-512 OEM20048004320050025616.0
Parhelia-512 Retail22048804352055025617.6

Let me call your attention to a few key numbers here, so you can see how Parhelia's final specs are likely to affect its performance in 3D applications.

  • Peak pixel fill rate — Because of its relatively low core clock speed, Parhelia's pixel fill rate—its raw ability to draw pixels onscreen—is lower than many of its competitors. At 880 Mpixels/s, it's slower than even a GeForce4 Ti 4200 or a Radeon 8500LE, in fact. Pixel fill rates alone aren't generally a limiting factor in high-end graphics cards, but they are worth noting.

  • Peak texel fill rate — The more important number in many respects is a GPU's peak texel fill rate, or its ability to draw textured pixels onscreen. Here, the Parhelia has everything else outclassed thanks to its four texture units per pixel pipe. Even the mighty GeForce4 Ti 4600 is over 1000 Mtexels/s behind.

  • Texel fill rate with two textures — This number isn't actually listed on the chart. However, in reality, this number may be more important than the other two numbers above. To get this number, simply multiply a chip's pixel fill rate by two—all the cards have at least two texture units per pipeline. This number is key because lots of current 3D applications and games only lay down two textures per rendering pass, so this number determines actual performance in a lot of cases. And here the Parhelia's lower GPU clock speed is a real sticking point. At 1760 Mtexels/s, the big Matrox chip runs well behind the Ti 4600 (2400) and the Radeon 8500 (2200). Once more, even the Ti 4200 and the Radeon 8500LE chips (both at 2000 Mtexels/s) are faster. Keep this in mind as the benchmarks unfold.

  • Memory bandwidth — We've long said that memory bandwidth is the primary limiting factor in terms of pixel-pushing power, and the Parhelia has gobs more memory bandwidth than the competition. However, we have to wonder how well the GPU can take advantage of all that bandwidth when it's not using all four texture units at once.

    Not only that, but efficient memory controllers and techniques like Z-buffer compression and (especially) occlusion detection (a/k/a hidden surface removal) have helped the latest NVIDIA and ATI chips alleviate the memory bandwidth bottleneck. Parhelia has a highly optimized memory controller, but it lacks occlusion detection. Regardless, memory bandwidth isn't likely to be a significant bottleneck for Parhelia cards right now.

So what does this festival of bulleted points tell us? In a nutshell, this: If an application can't make full use of Parhelia's four texture units per pipe, expect the benchmark results to look a bit pokey. If an application can use all four texture units, then duck.

Well, OK, maybe you don't need to duck. After all, we are dealing early revisions of Parhelia drivers. Past history tells us there's probably lots of room for optimizations and improvements in any early-rev graphics drivers.

Now, without further ado, let's look at the few benchmarks we've had time to run on this thing.