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Nvidia: We're not hobbling CPU PhysX | Page 1

Nvidia has hit out at claims it's deliberately hobbling CPU PhysX, describing the reports as "factually inaccurate."

Speaking to THINQ, Nvidia's senior PR manager Bryan Del Rizzo said "any assertion that we are somehow hamstringing the CPU is patently false." Del Rizzo states that "Nvidia has and will continue to invest heavily on PhysX performance for all platforms - including CPU-only on the PC."

The response follows a recent report on the Web claiming CPU-PhysX was unnecessarily reliant on x87 instructions, rather than SSE. The report also suggested PhysX wasn't properly multi-threaded, with the test benchmarks showing a dependence on just one CPU core.

Let's start with multi-threading, which Del Rizzo says is readily available in CPU-PhysX, and "it's up to the developer to allocate threads as they see fit based on their needs." He points out that you only need to look at the scaling shown in the CPU tests in 3DMark Vantage and FluidMark to see that CPU-PhysX is perfectly capable of scaling performance as more cores are added.

However, he notes that the current PhysX 2.x code "dates back to a time when multi-core CPUs were somewhat of a rarity," explaining why CPU-PhysX isn't automatically multi-threaded by default. Yet despite this, Del Rizzo says it's easy enough for a developer to implement multi-threading in PhysX 2.x.

"There are some flags that control the use of 'worker threads' which perform functions in the rigid body pipeline," he says as an example, "and each NxScene runs in a separate thread."

The point appears to be moot in the long-term anyway, as Nvidia is apparently planning to introduce new automatic multi-threading features in the forthcoming PhysX 3.0 SDK.

This "uses a task-based approach that was developed in conjunction with our Apex product to add in more automatic support for multi-threading," explains Dell Rizzo.

The new SDK will automatically take advantage of however many cores are available, or the number of cores set by the developer, and will also provide the option of a "thread pool" from which "the physics simulation can draw resources that run across all cores."

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Tags: physx, central processing unit, nvidia