Silicon Valley chip expert David Kanter has hypothesized that PhysX diminishes CPU performance by "exclusively" using an outdated x87 instruction set.
"x87 has been deprecated for many years now, with [both] Intel and AMD recommending the much faster SSE instruction [set]," Kanter told TG Daily in an e-mailed statement.
"On modern CPUs, SSE can easily run 1.3-2X faster than similar x87 code. By using x87, PhysX diminishes the performance of CPUs, calling into question the real benefits of PhysX on a GPU."
Kanter - who performed a detailed analysis of the instruction set - also acknowledged that Nvidia was free to "hobble" PhysX on the CPU by using single, rather than multi-threaded code "if it wished."
"[But] that choice does not benefit developers or consumers, and casts substantial doubts on the purported performance advantages of running PhysX on a GPU, rather than a CPU.
"[Still], for Nvidia, decreasing the baseline CPU performance by using x87 instructions and a single thread makes GPUs look better. This tactic calls into question the CPU vs. GPU comparisons made using PhysX; but the name of the game at Nvidia is making the GPU look good, and PhysX certainly fits the bill in [its] current incarnation."
However, Nvidia spokesperson Bryan Del Rizzo told TG Daily that Kanter's theory was "factually incorrect."
"Since the acquisition of PhysX, [we] have and will continue to invest heavily [in] PhysX performance for all platforms - including CPU-only on the PC. [But], we cannot become dependent on any hardware feature like SSE after the first revision has shipped.