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.

Re:Perspective Please

[tlhIngan]

Untill recently, the clock speed was only 222, now they have upgraded it so it can go to the full speed of 333mhz, however, you can't do this while running the wi-fi. People have not found a floor, just a limit to the extra given in the new update, everything was working fine at 222mhz and no one complained about slowness so you should have no problems on the wi-fi, there just wont be the extra snapiness, sony probably only did this to save battery or something.

Except if the game needs the full speed (the bus/CPU/GPU speeds are all locked together - at 222MHz CPU, it's 111MHz system bus, at 333MHz, it's 166MHz system bus). I can't remember what the system-bus-to-GPU ratio is (I think it's x1 system bus frequency).

So it makes multiplayer interesting - if things get busy, you can have the game become choppy because the models are too datailed for the GPU, while it may be adequate in single player because the GPU can render everything fast enough.

It's an interesting limitation - but the whole homebrew community has unlocked 333MHz practically from day 1 - I don't recall there being any sort of issue with wifi at that speed. Perhaps it really is battery life... but would 333MHz plus WiFi make that big of a difference? (If so, it means WiFi already takes a lot of power... in which case you get better battery life turning it off. If not, then the extra 50% in speed, WiFi will take little in comparison?).

Homebrewers have known this

[geekboy642]

Almost since the first hack came out opening up the PSP to hobbyists, it's been known that overclocking the PSP's chip will break the wifi. There's been a lot of speculation about it, with a lot of people thinking it was intentional on Sony's part. Well, I guess now we know. It's UNintentional, but still Sony's fault.

Heh, stupid closed rental-hardware company. They too will fall into obscurity.

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.