PS3 Has “Tight memory, Poor IO Performance” – John Carmack

[zarx]

mjk45 said:

zarx said:

The blame lays between the nature of megatextures and the limitations of the hardware. Virtual texturing does one thing well and that is allowing every inch of the game world to be uniquely textured so no 2 areas look the same. Unfortunatly that come with several dissadvantages vs traditional methods the first is that as every inch of the world has it's own texture you have to load in the texture data for every inch of the world and also store unique texture data for the entire world which leads to very large texture data which is why the game is 22GB now as RAM on consoles is very limited you can't keep a lot of that data in memory so you have to load each section of the world as you look at it.

This makes IO performance veery imortant for RAGE now the PS3 is known to use 2 main weaknesses which is the slow read times of the Blu ray and also some issues with the HDD formating which limits the advantages of the HDD and also the limitations of the partitioned RAM which makes memory mangagement an issue when you have very large data sets. This leads to texture pop in being a slightly bigger issue on PS3 than a fully installed 360 version which can use the faster HDD IO and full install to reduce texture load times. Now RAGE on PS3 does use something to mitigate these issues by using the CELL to transcode textures faster but there is only so much difference that can make.

It will be interesting to see how the tech performs in the 30fps enviroment of Doom 4 as that will give the engine twice as long to load in texture before rendering the next frame so there should be far less pop in in that game. Alternatively if you used an SSD in the PS3 that could improve the pop in issues a lot, but they are expensive.

As for the PC version well that is just a bad port as by default the game only uses 600MB of RAM to cache textures even if you have a system with 4GB+ RAM. Add in the generally poor OpenGL drivers compaired to Direct X and you get basically the same performance as the consoles at a higher resolution which to a PC gamer is horrible. The fact that AMD put out the wrong driver at launch didn't help ether. The next patch should make the PC version much better looking tho with the new texture upscalling which will aliviate the blurry textures.

Interesting read, one of the things that troubles me is people forget that in the case of 360 the HDD is not universal and it would also be interesting to know what percentage of people on 360 actually install the game , but the tech reviews are never undertaken on say , one with no HDD ,one installed ,one uninstalled , I understand why but it would be nice  to see the differences. Concerning the HDD there shouldn't be a major difference after all the PS3 uses standard 2. 5"  laptop drives, I remember Sony talking about lack of memory for PS2 not being so big an issue  because it could swap memory in and out real fast because it had big fat pipes and used that same mantra again with the PS3, if this was true you would think mega texturing would be right up it's ally ,then again we live in the real world, I like many had high expectations for this tech especially it's low memory benefits, Simply put Rage was probably the wrong type of game to show it off apart from the Framerate side, and yes your right bring on Doom 4  at 30fps , I wonder what the people on here who  think that 60fps on console and it's attended short comings is better than 30fps and cleaner graphics think of that decision , looking back I have come to the conclusion  that like many Multiplats you can get to your baseline easier on the 360 and end up good across the board with PS3 you can get results in certain areas that equal or better the 360 but not across the board and not so easy and not when you have to maintain a certain parity not just game wise but time and resources wise after all its a multi platform engine, if you wanted the best outcome especially for the PS3 you would have them make two separate dedicated engines each built from the ground up for the  two platforms.

The trouble with 2 seprate engines is the fact that you then also have to tune your assets to each engine and in the end you are basically making 2 seperate games which defeats the advantages of going multiplatform which is being able to use the same work to sell to a larger potential audience.

The HDD issues on PS3 isn't so much bandwidth but latency due to file fragmentation as explained by digital foundry

"The PlayStation 3 doesn't do this: when a game or demo installs to your HDD, there can be thousands of smaller files (in the case of GT5, up to 44,000 files) which does mean that over time your drive can fragment and drive performance will degrade a lot faster. In a recent discussion with a game developer who developed a data-heavy open world game, their extreme stress tests on the PS3 HDD actually reduced performance to lower than that of streaming in the same assets from Blu-ray. In order to show Rage running at its best, we formatted our HDD and gave the game a best case scenario from which to run - a completely empty drive - but it was still found wanting compared to the 360 full install, and wasn't orders of magnitude better than the 360 running from disc with HDD cache. "

As most people won't go to the trouble of formatting their drives to play RAGE at it's best most PS3 gamers will have significant issues especially if they have a large drive with a lot of games installed.

As for the faster RAM that doesn't really help if the source of the files is slow and you need to load textures as quckly as possible constantly. And while swapping between main and VRAM is very fast on PS3 it is still an added latency over a unified RAM pool which doesn't have to swap at all. Also while assets are swapped between the 2 RAM pools on PS3 the assets are basically taking up twice as much memory as at least part of the file will be in both pools further exaserbating the fact that the PS3 has 10MB less total RAM and a slightly larger OS and the added overhead of having 2 seperate RAM page tables. Th bottom line is that the PS3 is really hamstrung by it's RAM ironically it's probably the only thing they skimped on and it's come to bite them in the arse when combined with the higher latency and slower average read speed of blu-ray. If they had gone with more RAM vertually every multiplatform game would look and run better on PS3. They seem to have recognised the mistake as the Vita has 256+512MB of RAM, and from the sound of things the Wii U also has a lot more RAM which will likely be it's key advantage against the current generation. It will be interesting to see what happens next gen with MS and Sony just about every dev is asking for 4GB+ RAM for next gen, every time a dev is asked what they want from the next gen more RAM tops the list, some devs like Crytek and CCP want 8GB of RAM and I think they would be wise to follow devs wishes.

Anyway I should probably quit my (know just enough to get me into trouble) techno nerd rants.