Bethesda: Divided memory pool causes lag for Skyrim PS3; explains the issue in detail

Bethesda recently released patch for the PS3 version of Skyrim to alleviate some of the issues gamers were facing, notably the low framerate that supposedly made the game playable. The patch, while extremely helpful, still did not completely fix this problem. Digital Foundry confirmed that these issues still exist.

So what causes this problem? As you know, Skyrim has a persistent world. Which means, if you kill some guy, his body will still be there at the same location. While this makes for immersive gameplay, the PS3 cannot simply handle this due to RAM issues.

It’s a known fact that the PS3 has a divided memory pool; 256MB  for the CPU and 256MB is for the GPU, and the GPU RAM can also be used for other tasks. Now the Xbox 360 has an unified 512MB RAM so it makes it easier for developers distribute the tasks well.

Fallout: New Vegas lead developer explains this in more detail.

“It’s an engine-level issue with how the save game data is stored off as bit flag differences compared to the placed instances in the main .esm + DLC .esms. As the game modifies any placed instance of an object, those changes are stored off into what is essentially another .esm. When you load the save game, you’re loading all of those differences into resident memory,” he revealed.

“It’s not like someone wrote a function and put a decimal point in the wrong place or declared something as a float when it should have been an int. We’re talking about how the engine fundamentally saves off and references data at run time.

“Restructuring how that works would require a large time commitment. Obsidian also only had that engine for a total of 18 months prior to F:NV being released, which is a relatively short time to understand all of the details of how the technology works.

He also mentioned why the save data size keeps on increasing.

“Individual bits of data are tiny, but there are thousands upon thousands of objects in F:NV, each one containing numerous data fields that could potentially be changed in your save game. Over time, it adds up,” he said.

“As with Fallout 3 and Skyrim, the problems are most pronounced on the PS3 because the PS3 has a divided memory pool.”

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[Bethesda forums]