Nvidia: We're not hobbling CPU PhysX

SSE will soon be enabled by default

In addition to the new multi-threading features, Del Rizzo also says "SSE will be turned on by default" in the new SDK. However, he notes that "not all developers want SSE enabled by default, because they still want support for older CPUs for their software versions." The original

Why do games developers still want to provide support for CPUs that are over ten years old? Del Rizzo says it's up to the game devs and what they demand, but he reiterates that it's definitely not a deliberate attempt to hobble CPU PhysX.The original report by Real World Technologies showed the Dark Basic PhysX Soft Body demo (below) made heavy use of x87 instructions, rather than SSE.

"We have hundreds of developers who are using PhysX in their applications," he says, "and we have a responsibility to ensure we do not break compatibility with any platforms once they have shipped. Historically, we couldn't become dependent on any hardware feature like SSE after the first revision has shipped."

He also points out that the PhysX 2.x SDK does feature at least some SSE code, and SSE isn't necessarily faster anyway. "We have found sometimes non-SSE code can result in higher performance than SSE vector code in many situations," he says. However, in the long-term SSE will apparently be the way forward for CPU-PhysX in the long term. "We will continue to use SSE and we plan to enable it by default in future releases," says Del Rizzo.

In short, it looks as though there's a fair bit of legacy detritus in the current PhysX SDK, partly due to the demands from games devs. Nevertheless, there are already ways in which developers can use multi-threading in CPU-PhysX, and full SSE support and improved multi-threading will be coming shortly.

This doesn't look like a company trying to deliberately cripple CPU-PhysX to make its GPUs look good.