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Discussion Starter #1
The biggest reason isn't performance, but memory footprint. The XBOX has 64 MB of unified memory. Any leading-edge game will fill all the memory with sounds, textures, frame buffer, etc. There isn't enough memory left for the high-def modes.


For example:


Each pixel displayed requires (at the minimum):


2 bytes for the front buffer (16-bit color buffer)

2 bytes for the back buffer

2 bytes for the z buffer (16-bit zbuffer)

= 6 bytes per pixel

(BTW, for 32-bit color and zbuffer, that 12 bytes per pixel!)


With a 480p, this means the screens use


640x480x6 = ~1.8 megabytes


for 1080i, this means the screens use


1920x1080x6 = ~12.4 megabytes


That's a _huge_ difference. I tested a game that could run at 1080i. It looked unbelievable on the XBOX, but that version of the game wouldn't run on retail xboxes.


BTW, it is theoretically possible to cut the footprint in half by using field mode instead of frame mode. In practice, it is incredibly difficult to program a game to use field mode since that means each field must be completed in less than 1/30th a second to keep from seeing artifacts. Doing this is difficult even at 480i, let alone 1080i.


Richard G
 

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Discussion Starter #3
The hardware is certainly capable of it, it is just impractical. I wouldn't be surprised if a game did support 720p or 1080i. I just don't think most games will.


Richard G
 

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re: game played at 1080i


It was NASCAR Heat. I was the leader of the team that worked on it. When we were testing the HDTV pack, we made special versions of the game for fun. One ran at 720p and the other ran at 1080i. They both looked beautiful, even though we had to turn off antialiasing to get a reasonable frame-rate. I hooked it up to my LT150 projector system. It was stunning @ 16:9/1080i. I was really impressed with the quality of the signal from the XBOX. Rock solid and great color fidelity. It really is a shame that the DVD player doesn't support the progressive modes. It really was spectacular, even on my system that doesn't have enough resolution for true 1080i.


Richard G
 

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want to sell the "special edition" on nascar heat in 1080i?
 

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Quote:
Originally posted by Richard G
With a 480p, this means the screens use


640x480x6 = ~1.8 megabytes


for 1080i, this means the screens use


1920x1080x6 = ~12.4 megabytes


That's a _huge_ difference. I tested a game that could run at 1080i. It looked unbelievable on the XBOX, but that version of the game wouldn't run on retail xboxes.
I'm sorry if I offend, but I have to wonder whether you really know what you're suggesting you know about.


The Xbox wouldn't, or shouldn't render anything at 1920x1080 in order to produce a 1080i output resolution. The most it should ever render with the GPU to send to the outputs is 1024x768, since that is the maximum input resolution of the Conexant HDTV encoder chip in the Xbox. All of the extra pixels rendered at anything above this would be entirely wasted, and I would hope that the leader of the team that worked on the game would know this.


I'm not trying to start anything... I just would hate to be naive and blindly believe. Comments?
 

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Just curious regarding the last comment --


What in the world does the XBOX have a Conexant HDTV encoder chip for?????


The NVidia GPU is quite capable of outputting the YUV signal and sync timing and is akin to running my Geforce 3 into my HDTV??? What am I missing here?


-Jon
 

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I could be wrong, but I though the chip was for TV encoding NOT HDTV encoding. And yes it is capped at 1024x768 as most transoders for TV are.
 

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I agree,


so....if the Conexant chip is responsible for TV transcoding (ie., transcoding to NTSC), then the XBOX could very well still run at resolutions higher than 1024x768 for HD displays (the TV out would simply not work in this case).


-Jon
 

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Richard G wrote:


"it is theoretically possible to cut the footprint in half by using field mode instead of frame mode. In practice, it is incredibly difficult to program a game to use field mode since that means each field must be completed in less than 1/30th a second to keep from seeing artifacts. Doing this is difficult even at 480i, let alone 1080i."


Not sure on the Xbox, but for us on the PS2 this was relatively painless. We use a full height backbuffer at 24bit and a half height front buffer at 16bit. The only "difficult" part is making sure that we stay at 60fps. The full height backbuffer is a fallback so that if we drop frames we don;t have to rely on the internal line doubling. In any case, the point I think all the developers are making is that when a new release of harware comes out there is an expectation of more characters on screen, more detailed textures, more animation etc. and these suck up resources that could be used to go HD. If the games looked the same but ran in HD this would not impress the general public. It's still going to be problem even when they load machines down with RAM, as there is constant competition for the memory. Perhaps we'll start seeing "variations" of games in HD, that is in HD it would be rendered in 16bit, fewer textures, less things on screen, etc. but that kinda defeats the purpose.
 

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Guys,

I appreciate all the technical info you are giving us, but for the uneducated dummy like me, does the Xbox support HD or not?

I purchased the Xbox because it is supposed to support HD.


This is from the Xbox webpage:
http://xbox.com/support/default.htm


"Does the Xbox support HDTV?


Xbox was designed with high-definition TV support specifically in mind. Xbox supports HDTV and TV resolutions up to 1920x1080 with the purchase of the High Definition AV Pack.


The High Definition AV Pack supports HDTV RGB video and your choice of RCA Audio or Digital Audio over optical cable."


Thank you for your help.


Carlos
 

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Discussion Starter #15
Adebar -


Even if I would sell you a disk, you won't be able to use it. You need a debug station that is available only to publishers and developers. We can't burn DVDs that run on retail units.


binaryfarms -


Maybe I wasn't clear. On the xbox, it is easy to set the game up into field mode, it is making it look good there. Dropping below 60 fps looks awful in field mode, IMO. As you probably know, it is hard to design a 3D game that maintains a level frame rate. On the older consoles (Genesis, SNES), it was much easier.


Richard G
 

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It seems to me the real question is why did Msoft design the XBox with only 64 MB memory? I can buy 256 MB of DDR for $35.


Or, when will I be able to play the XBox games on my Pentium4 based PC?


Msoft should have designed the games for PC use. Every XBox they sell has to be costing them money, so if they could just sell the software they would make more money.


-phil
 

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Quote:
Originally posted by PhilB
It seems to me the real question is why did Msoft design the XBox with only 64 MB memory? I can buy 256 MB of DDR for $35.

-phil
Keep in mind that DRAM prices have dropped somewhere around 90% this year. At the time the XBox was being designed, the price of DRAM was at a level where any more than 64MB would have been really cost prohibitive.


Rodney
 

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I would think a more practical resolution would be 960x540p, which is used by the DTC-100. Many HDTVs already convert non HDTV material to this anyway.

I thought I read that the next TEST DRIVE game (not off-road) would be 1080i....
 

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Richard- point taken on the field rendering and locking frame rate at 60. Same problem here.


PhilB- The rumor is that Xbox is a loss leader to get into the publics living room, and it looks like this is sony's plan as well. This generation of xbox will probably not turn a huge profit, if it does at all it will be software and license agreements. This is typical of consoles, except Nintendo, who do manage to make money on hardware.


Comparing console RAM to PC RAM is really apples and oranges. Often the ram is right on the board to get better bandwidth, it's not just a standard socket kinda deal where thay can use normal PC100 RAM or similar. But yes, it would be nice for the next round of consoles to have, say, a gig of ram. It won;t happen, but it would be nice.
 

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I tried to find photos of the inside of XBox, but no luck. I did find some details of a deal between Msoft and Micron to supply the XBox memory. According to the article, the XBox uses standard 200 MHz DDR SDRAM. 8 2Mx32 chips are used on some sort of modules (I think it was two modules). I don't know if they are standard DDR DIMMs, but if so it'd be interesting to swap them with larger modules.


Has anyone seen the inside of the XBox? Richard G, did you get a look? What do the memory modules look like?


It's not necassary to populate the memories right on the mainboard. Standard memory drivers are designed to handle ~6" of traces.


As far as the loss leader goes, that's exactly my point. Now, if the games were PC friendly (shall we say PC PC?), then Msoft could sell the games and set up license deals and not have to take a loss on the consoles.


-phil
 
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