Doom3 on Xbox...and Costs of Gaming

[Symbea]

I found this interesting read on the PVC Board. Huge credit goes to TRAGIC from PVC for typing this up. I personally found it interesting because how can a game that takes the highest grade PC available be on Xbox which is relatively less powerful to some PCs today and have the same graphical look and run perfectly fine? Once again, credit goes to TRAGIC from the PVC Boards.
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Want to know why DOOM3 and games like it can run on xbox? This may seem like a long post but if you read it will probably clear up alot of questions on the power of your xbox and the potential for incredible looking games that you may not have thought could run on it. But it's up to developer's to use it. And show this to the next person who say's: "The xbox is just a downgraded PC". That is such a false statement.

NOTE: I don't post this to "slam" PC tech, or to kick off a heated debate - flame responses will be ignored. I post this for informational purposes only, as it's a subject that I personally find interesting.

A while back I posed the question in the title to this forum, to see if any of the professionals who post here could let me know how the XBox could render Doom 3, and I quote Carmack here, "just fine". Recently, it's been noted that Carmack said that the XBox should be able to run Doom 3 with no graphical downgrade from the PC version. I was struck by how remarkable a claim that was. How could a box with a 733 MHz Pentium 3, an NV2A (Geforce 3 plus one vertex shader), and a total of 64 MB of ram under the hood possibly run Doom 3, when I knew that my PC, with specs that blow the XBox away, would in all likelihood render Doom 3 like a slide show at medium details? (A presumption, maybe, but come ON...)

I got a few responses, but the only one that seemed to make any sense at all was "bloated code". Basically, that since game developers had to code for such a variety of hardware on the PC, that the code could not be as efficient as it was for a fixed hardware platform like the XBox. As someone who works in a technical field, this made a degree of sense, but it didn't sit very well with me - weren't APIs and device drivers supposed to eliminate that sort of "hardware specific" code problem on the PC? Even if they didn't solve it altogether, why would it make THAT much difference to performance? I mean, my PC has got, between the system RAM and video RAM, TEN TIMES the memory of the XBox, and a CPU more than TWICE as fast. There had to be a better explanation, right?

I found one in a magazine sold here called "CPU - Computer Power User". They employ a number of PC hardware and software dudes/dudettes to write regular columns for them - people like Alex "Sharky" Ross, Anand Lal Shimpi, Kyle Bennet, and others. One of their regular columnists, Alex St. John - who the magazine lists as "one of the founding creators of Microsoft's DirectX technology", wrote a column in the Feb 2003 issue of CPU titled "XBox vs. PC: Fight!" in which he compares the XBox's capabilities with that of the latest high-end PCs in terms of 3D processing (it's worth noting that the guy no longer works for Microsoft). Turns out, it's more than just about screen resolution. Here are some excerpts:

How much video bandwidth does an XBox need to play Halo on your TV vs. on a PC?

PC: 60fps X 1024 X 768 X 32-bit color = 180 MBps
XBox: 30fps X 640 X 480 X 16-bit color = 18MBps

WHOA! The PC needs to generate 10 times as much video data as a console just to properly drive the display. Unfortunately, the calculation I just did doesn't tell the whole story. We haven't touched the really thorny issue of video bus bandwidth.....

...The internal memory bandwidth needed to generate 180MBps of 3D video for modern video games is on the order of 2 to 4 GBps. To drive a dual-monitor system at 1200 X 1600 X 32 requires around 10 to 20 GBps of internal video bandwidth. By contrast, an 8x AGP bus on a PC has a PEAK bandwidth of 2.1 GBps.

This is where the PC architecture breaks down and $200 children's toys (consoles) really kick its butt. The PCs CPU has its own local RAM and system bus. The PC's GPU sits across the AGP bus from the CPU with a redundant cache of its own local high-performance RAM. This duplication of memory and buses adds unnecessary expense to the PC design. PC RAM on the CPU side is single-access memory; it can't be accessed in parallel like console video RAM can. The RAM on the video chip, on the other hand, is dual-ported; it can be read by the GPU while the AGP is accessing it. The AGP bus, in effect, creates a huge gulf between the CPU and GPU: They are essentially separate computers. Sending data from CPU RAM to GPU RAM is fast, but pulling data back across the AGP bus can force the GPU to stall, causing a noticeable frame rate drop. Thus, once the CPU has shipped data off to the GPU, it can rarely help out with processing again.

Contrast this with the XBox, in which the CPU and GPU share the same pool of dual-ported RAM on the same bus. Both the CPU and GPU can hammer on video data in parallel. The XBox memory architecture is actually broken into two parallel banks, each operating at system bus speeds, independently allowing a total peak bandwidth of around 6.4 GBps. There is no OS or virtual memory management slowing things down. The result is that the XBox probably sustains 75% of its peak bandwidth continuously. The CPU can augment the GPU and add features to it in software that may not be hardwired in. All of the XBox's 64 MB of RAM is video RAM shared by the CPU. The PS2, by contrast, has 32 MB of RAM, 4 MB of which is dual-ported RAM shared by the CPU. The XBox and the PS2, to a lesser degree, can also store some large 3D data types, such as textures in compressed formats that the GPU can decompress on the fly, thus increasing effective video memory bandwidth another 3-5x...

He goes on to talk about how PC games must be coded to be capable of running on low-end graphics processors, which keeps the PC gaming market skewed to the low end. He also makes mention of some games utilizing a method of real-time shadowing that demands video data to be swapped back and forth over the AGP bus three times, resulting in a huge performance hit. Then he summarizes:

...So why does a two-year-old console architecture like the XBox sold for $200 in KB Toys kick a modern PC's butt for gaming?

1. The PC starts off with huge bandwidth disadvantage because of the demands of its display technology.

2. The XBox has an incredibly powerful video architecture.

3. The XBox CPU is not burdened with the baggage of running a giant memory and CPU consuming OS.

4. Every XBox comes with a great standard video chip, but most consumer PCs are sold with a crippled video chip, which drags down the whole PC game market.

5. A shared memory architecture between the CPU and GPU lets both processors help with graphics performance, while even the fastest AGP bus on the PC is a bottleneck. The next time somebody tells you an XBox is just a chopped-down PC, show them this column. They couldn't be more wrong.

So..quite interesting. Sure there is alot of technical things in it and it's long but most people should understand what he was talking about.

[Rocks316UK]

I read smothing like this that told you how the ps2 can make the graphics for gt4 so real.

I also looked at the detailed spec of the ps2 and it looks like it can out perform the Xbox!

Belwo is the information i am very suprized that this can out perfrom my xbox.

I was browersing the xbox's forms and just looking for ideas for a new xbox game when i found this post about the ps2.

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The CPU
Of course, the Central Processing Unit, the heart of every computer or console. Most of the calculations take place here. The XBox has a Intel processor which runs at a clock-speed of 733MHz. That's a lot higher than the 300MHz at which the PS2 CPU is running. But does that make the CPU better? Not at all...
Here's why the PS2 CPU (Emotion Engine) is a lot more powerful:

-Data bus, cache memory as well as all registers are 128 bits on the PS2 CPU while the XBox CPU is 32 bits.
-It has a max. performance of 6.2GFLOPS while the XBox CPU can only do a bit over 3 GFLOPS.
-It incorporates two 64-bit integer units (IU) with a 128-bit SIMD multi-media command unit, two independent floating point vector calculation units (VU0, VU1), an MPEG 2 decoder circuit (Image Processing Unit/IPU) and high performance DMA controllers. Yes, this is all on the emotion engine itself.

Okay now what does this mean? It means that the PS2 can handle heavier physics and 3D engines (and can do more accurate realistic visual effects like splashing water and explosions). It also means that the PS2 can handle a lot more sophisticated Artificial Intelligence programming so that you have intelligent human-like opponents. And with a floating point calculation performance of 6.2GFLOPS/second, the overall calculation performance of this new CPU matches that of a super computer. This is a completely new CPU architecture especially designed for sophisticated graphics and physics while the architecture of the XBox CPU is pretty old and simple (it's a little less powerful than a standard PentiumIII processor). The architecture of the Emotion Engine really is very sophisticated so I'm not going to explain it in detail here. But simply put the main advantage of the PS2 CPU is that it is subdivided into lots of other tiny powerful processors, all of them designed to do a special task and almost all of them can work independently from eachother. And another thing... the processor inside the box does not say "Pentium III" anywhere. It simply reads "Intel". The XBox's processor is NOT an Intel Pentium III, as Microsoft would have you believe, but in fact a Celeron II. It is a 700mhz Celeron, complete with 128kb of L2 cache (P3 coppermines actually have 256kb L2 cache), but overclocked to a 133mhz FSB, resulting in PIII/Celeron hybrid. What makes it a Celeron II is the fact that it is still using a Coppermine Core, with 8 way set associative L2 cache rather than your typical Celeron 4 way set Level 2 cache. What it ultimately comes down to is that this Coppermine core, which allows Microsoft to market the XBox as a PIII Coppermine, is about a 10% speed increase over the Celeron equivalent of this processor. Is the XBox CPU a Celeron? Not really. Is it a Pentium III CPU in the sense that everyone thinks of a PIII Coppermine? Nope. It's somewhere in between and while it is great to run standard applications and some PC games on the side, it's not a good thing to have it as a CPU in a gaming console...


The Graphics Chip and VRAM
This is where the images are rendered. The XBox uses an Nvidia Graphics Processing Unit running at 250MHz and the PS2 uses the Graphics Synthesizer running at 150MHz. Again, judging by these specs the XBox looks better. The XBox GPU has a few advantages (or maybe not) over the PS2 GS, for example:

-The XBox GPU can do 125 million polygons (according to Microsoft) while the PS2 GS can only do 75million polygons
-The XBox GPU has a max. resolution of 1920x1080 and the PS2 GS can do 1280x1024, the rest of the graphics chip will be comparable to NV-20 chip.

There are alot of neat effects the XBox GPU can do with its hardware, but all those effects can be done by the Emotion Engine in software too (while the XBox' CPU is not powerful enough to do complex visual effects in software). But the catch is that these advantages (talking about higher resolutions here) don't make a lot of difference on a TV screen, even on an HDTV screen the difference would be barely noticeable (when the console's hardware is used properly). So, is the XBox Graphics Processing Unit better than the PS2 GS? It doesn't look like it, the architecture of the PS2 GS looks far more advanced. For example, PS2 has a parallel rendering engine that contains a 2,560 bit wide data bus that is 20 times the size of leading PC-based graphics accelerators. The Graphics Synthesizer architecture can execute recursive multi-pass rendering processing and filter operations at a very fast speed without the assistance of the main CPU or main bus access. In the past, this level of real-time performance was only achieved when using very expensive, high performance, dedicated graphics workstations. There is a 48-Gigabyte/sec memory access bandwidth achieved via the integration of the pixel logic and the video memory on a single high performance chip. The quality of the resulting screen image is comparable to high quality pre-rendered 3D graphics. (that is once the game developers have learned how to use it properly) There has also been a misunderstanding about the VideoRAM on the PS2. The VRAM is included in the 32MB of main RAM on the CPU (the developer chooses how much of it he wants to dedicate to VRAM). Everyone thought the 4MB of memory on the GS was the VRAM while that is just a buffer in which all the rendering is done so no external bandwidth is needed (only for texture streaming). Another rumor that's been spread by several gaming sites is that the XBox is capable of texture compression and full scene anti-aliasing while the PS2 isn't. This is simply not true. The PS2 can compress/decompress textures and do full scene anti-aliasing without causing as much slow-down as on the XBox. And although the XBox GPU can do a lot of effects that are not 'built-in' in the PS2 GS, the PS2 can do all these effects and more in software mode (but at least at the same quality) through the Emotion Engine. XBox fanboys will probably tell you that the XBox GPU is more powerful because of its vertex shaders while the coprocessors on the Emotion Engine of the PS2 can be used to get the same effects as the XBox' vertex shaders (but the vertex shaders can't do everything that the EE's coprocessors can do).

Now let's take a look at how Microsoft got the idea that their graphics chip can do 125 million polygons, because this is a little unclear... (I'm going to go in some tech details now) The PS2's Graphics Synthesizer has the highest pixel fill rate of the next generation of consoles. Most remeber the 4.0 GPixels on Microsoft's spec comparence sheet. Well, Microsoft was nice to include a "(anti-aliased)" next to it. What does "4.0 GPixels (anti-aliased)", mean? It's misleading. The Xbox has hardwired 4x FSAA, when this is turned on the actual total of 1.0 GPixels is re-rendered 4 times to remove aliasing. Another possible reason for Microsoft to say Xbox's fill-rate is 4 GPixels per second. Is that the 1 GPixels is with 2 texture layers, if it is NOT used Xbox would not gain any performance and if it is used Xbox wouldn't lose any performance. It remains 1.0 GPixels w/ 2 textures, so what MS possibly did was it doubled the fill rate twice. Trying to compare it to PS2's fill rate w/ no texture. What MS did was it came up with misleading numbers. The Xbox can't go higher than 1 GPixels per second. The NV2a in the Xbox has 4 pixel units running at 250 MHz, that's 1 billion pixels/second. While the GS in the PS2 has 16 pixel units running at 150 MHz, which is 2.4 billion pixels every second. Now let's talk about polygons. Right here I'm talking about polygon rendering and not polygon transformations. To calculate polygon rendering performance, you take the pixel fill rate, and write it in millions. So PS2s pixel fill rate is 2400 Million. When Sony says polygons, it is refering to 32 pixel polygons. Divide 2400 Million by 32. You get 75 Million (32-pixel) polygons per second. That is raw and doesn't include textures, they use up pixels also. Now let's take Microsoft's allegged pixel fill rate of 4000 Million, which MS has on it's spec sheet and divide it by 32, you get, yes you guessed it, 125 Million (32 pixel) polygons per second. Here's the problem, the NV2a doesn't have a 4000 M fill rate but a 1000 M fill rate. So it's 31 Million (32 pixel) polygons per second. This isn't raw, since there's also 2 texture units for each pixel unit. So that's 31 million with 2 texture layers, the PS2 is around 38 Million with 1 texture layer and 20 million with 2 texture layers. The Xbox maxes out at 31 MPolygons per second, if textures aren't placed on those polygons- Xbox will not gain a polygon rendering increase in performance. The PS2's Graphic Synthesizer could render 75 MPolygons per second with no texture. The NV2a in the Xbox can't render higher than 31 MPolygons per second at all.

Think this article is complete bull? Check the facts with the official press releases and compare for yourself:
Sony press releases regarding the PS2 hardware specifications
http://www.psx2central.com/misc/psx2info.htm
Website where the developer interviews can be found
ps2.ign.com
XBox final specifications and info
http://www.activewin.com/faq/x-box.shtml#Microsoft%20"X-Box"%20Timeline
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I agree with you, in terms of graphics textures, the xbox wins, but that was'nt what I was talking about.

And can anyone get back to my question in the subject instead of abusing me for not being an Xbox zealot? I'm not a ps2 zealot either, I was just looking for some helpful information. Honestly, it seem's like all the Xbox owners are getting pissed off with Microsoft more and more by the day...

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Intresting if you ask me i wonder if they will ever tap ps2 full power.

[ May 08, 2003, 12:22 PM: Message edited by: Rocks316UK ]

[Symbea]

It's like I said before, it's not what the console can do, it's what it has done. By the time either console reaches it's peak, the next generation in consoles will be out. I guess you can say that Halo 2 and Doom III will push the graphics to it's peak but there is always room for improvment.

[Loakers]

i think we all underestimated the 2 consoles, but most of all we underestimated ps2. I think its evedent, especially recently, that its capaable of alot more than we took for granted, and it must be something to do with this lovely new coding that sony plan on making available to all companies.just see the gt4 pics.

doom 3 and dx2 are shaping up nicely on xb and i recon with a bit of engunuity they could be done on ps2, but would need built form ground up.
i recently viewed a beatiful ps2 bump mapping demo and it was nothign short of impressive and i think its great that a console thought to be ending it graphical peak has just tapped immense treasures of hidden power. i think sony news this all the long with there corprate slogan 'never under estimate the power of playsation'. Its even impressed the most hardcore of xbox fans, which is encouraging, maybe one day we'll all be un-biased in our opinions.

but its an exciting time. xbox is doing wonders, ps2 is beign wondrous and games are getting better and pusching the boundries.

the next teritory is ps3 and we'll see how far it pushes the boundary,, if it does not brake it.

i myself tho will be getting doom 3 for pc, dx 2 for pc, halo2 fo xb and gt4 on ps2.

[ May 08, 2003, 12:43 PM: Message edited by: loakers ]

[Symbea]

I wish I had a higher grade PC. There are so many games for PC that I would love to play but I can't. I'm glad that some of it's popular games are going to consoles though so I can play them anyways despite if they are old or not.

[Loakers]

i have sexy machine !

2.56 ghz, 512 ram, 80 gig hard disk , geforce 4 mx 440.

around christmas i'll be upgrading to a raedon ati 9700 pro. huzzah !

curses ! i have a head ache, oh, way off topic.

i was going to mention the latest games development on ps2. developers can port games to ps2 as sucessfully as they woudl like, and so the new trend is to creates its own game. the call of money must be too great, but apprentl ps2 is to get an exclusive deus ex game (nearly confirmed) and an unreal game of its own.

its all good !

if u cant port it, make a new one !

[Rocks316UK]

Xbox can easily do better graphics than halo 2 it's just they got to figure away of how to do it becuase it silly to think that a consoel can reach it peak in 2 years! Also my pc is.

AMD Duron 900 mhz
256 SDram Running at 133 mhz
20gb Hard Drive
Geforce Mx420 64md ram only cost me £27.99 NEW!

and me pc runs like a dream on these spec's. No slow down on game like Unreal 2 or anything evan on medium graphics. i think it is becuase i
defrag my pc alot and clean the reg out often

[ May 08, 2003, 02:28 PM: Message edited by: Rocks316UK ]