Hi, this is my first thread, but I have posted often about the recent development that the iphone will be a player in the handheld arena. As anyone whose read my posts knows, I am all for it, and I think the iphone can be a great gaming device. That said, there are many questions that need to be asked, not the least of which is: what exactly is the graphics potential of the iphone? I have heard people say it will be weaker than the DS, as well as others who say it will be stronger than the PSP. Clearly there is little consensus. I indend to offer a best guess as to what the iphone is capable of, and I hope to hear others chime in with what they think as well.
First off, it is necessary to outline what the iphone hardware is. The general consensus is that the iphone sports a powervr MBX graphics accelerator, a Samsund ARM11 cpu designed to run at 600mhz, but underclocked to 400mhz by Apple for battery life, as well as 128mb of RAM. I have no way of verifying this, but I have encoutered these number often enough in places like here that I believe they are correct. According to the powervr website, the MBX is capable of 3.7 million polygons per second, with a 300 million pixel per second fill rate. However, I've heard from other sources that this is conservative, and that the MBX is capable of more than 4 million polygons per second, with a pixel per second fill rate of more than 400 million. For those who don't know, more polygons allow for less blocky, more naturally shaped 3D objects. Think of mitten hands vs. hands with fingers. On the other hand, a higher pixel fill rate means more and higher resolution textures. Think a solid brown rectangle vs. a wood grained door. Thisis of course an oversimplification, but it's enough to get the idea.
Now for the competitors. The DS has an ARM9 cpu clocked at 67mhz, and a secondary ARM7TDMI processor clocked at 33mhz, as well as 4mb of RAM. What is interesting about the DS is that its polygon budget is capped at 2048 triangles a frame, or 120,000 triangles at 60fps.
On there other end of the arena, we have the PSP with a MIPS cpu clocked at 333mhz. Much like Apple, Sony originally underclocked the CPU to 22mhz in order to conserve batteru life, but now Sony allows developers to run the CPU at full speed. The PSP also has 32mb of main RAM. This was also recently increased to 64mb, but unlike to CPU overclocking, old PSP's can't suddenly grow more RAM. Developers still need to make their games fit 32mb. Also there is a dedicated multimedia processor for decoding video with2mb of dedicated video RAM, as well as a dedicated GPU with 2mb of RAM. The theoretical graphical peak for the PSP is 33 million polygons and a 667 pixel per second fill rate.
Clearly, the iphone can better the DS in graphics. Its main cpu is 6 times faster and is using a more modern architecture. Its graphics acceleration is capable of over 30 times as many polygons, and it has over 30 times as much RAM.
The story with the PSP is more complicated, not the least because they use different CPU architectures. At 333 and 400mhz, their clock speeds are very similar, with the iphone having a slight lead. Yet if the iphone were to remove the underclock (much like Sony did) then the difference becomes substantial, with the iphone being nearly twice as fast. I am not in a position to compare the different characteristics of the MIPS and ARM architecture, but I am confident in saying that the PSP and DS are close enough in the CPU department that it probably won't make much of a difference, seeing as how gaming is GPU limited, not CPU limited.
In the GPU department, Sony has a clear advantage. Since they are using a dedicated GPU with its own video RAM, it is capable of much higher bandwidth than the iphones intergrated solution. On paper, the PSP has about 8 times the polygons, and around twice the pixel fill rate. However, given Sony's historical tendency to overestimate their hardware, it is probably a bit closer.
By the numbers, the iphone is quite close to the PSP in terms of pixel fill rate, probably about as close as the PS2 was the the XBOX. However, on polygon pushing, it is quite a gap. Fortunately for the iphone, most modern games are texture constrained, not polygon constrained. Final Fantasy XII reportedly used only 5 million polygons per second, foucusing their resources more on lighting and textures. that's not much more than the iphones theoretical maximum.
Of couse, consoles never actually get close to there theoretical maximum, but the iphone has something that could help it get pretty close, and that is its large amount of RAM. Iphone developers won't need to compress nearly as much in order to fit their textures into RAM, or tax the CPU with decoding and procedural generation. This should allow the iphone to come closer to its theoretical maximum and/or reduce development cost.
All in all, the iphone is between the PSP and the DS as far as graphics goes, but much, much closer to the PSP. A game designed for a low poly art style could concievably rival most PSP software in terms of visual fidelity. Granted, graphics is only one part of the gaming equation, and I plan to get into the other aspects at a later time. For now, it is safe to conclude that the iphone is in a good place graphically. It is only a question of whether developers will push it to what it is capable of doing.
