PSP Wi-Fi Impairs Processor Speed

GameDaily reports that the PlayStation Portable has an interesting restriction: its full processor power cannot be utilized at the same time as its WiFi functionality. Therefore, games that are played online cannot make use of the chip's 333mhz processor speed. The original finding from Beyond 3D was confirmed to GameDaily by Sony. Dave Karraker, Sr. Director, Corporate Communications: "The recent firmware upgrade (3.50) that removed the restriction on the PSP's CPU speed enables developers to utilize speeds either lower or higher than the default 222MHz, up to the full 333MHz clock speed. The article is correct that increased CPU speed cannot be used with the PSP's wireless feature." Though speculation is that this is a power-saving decision, there has been no official announcement as to the root cause.

Comments

Probably an issue with clock reference

[pslam]

This sounds very familiar to me (I work with a lot of deeply embedded systems). What they've probably got is a clock in the WiFi which is referenced from the CPU clock. It could be the core clock for it or maybe used as a reference to generate the 2.4GHz signal.

So, when you change the CPU clock to 333MHz, the hard-wired multipliers for the WiFi clock don't work.

It could also be that the clock jitter at 333MHz is greater than at 222MHz, so the WiFi doesn't work even if the clock dividers/multipliers can be adjusted.

It could also be that they need to increase the core voltage to manage 333MHz, and that breaks some other aspect of the WiFi. Typically RF parts are very sensitive to these changes and the signal will end up garbled.

It could also be that the power regulator can't actually supply the total system power load required for 33MHz CPU and WiFi at the same time (WiFi is quite power hungry).

There's plenty of non-conspiracy reasons why this could be the way it is, and all of them are quite acceptable seeing as the part was only intended to be 222MHz in the first place. The fact that something doesn't work at 333MHz kind of validates the original rating.