Sony PlayStation Portable: 333MHz comes with restrictions

Friday 10th August 2007, 06:04:00 PM, written by Stefan Salzl

Following the news about the removal of the PlayStation Portable's MHz cap, which finally gave developers a free reign of the clock frequency of the CPU, Beyond3D was able to get some more details from its sources.

Two years after the arrival of the first PSP SDKs the infamous MHz cap, which limited the CPU's maximum clock frequency to 222MHz and the maximum bus clock to 111MHz, remained intact. Only in early 2006 those restrictions were altered: A new boot-mode allowed the SDKs to fully tap into the CPU by enabling the maximum frequency of 333MHz. However, the use of this mode was restricted to debugging purposes only.

With the release of the Firmware 3.5 a new clock control function was added and now the technical requirements checklist allows software to run at the full 333MHz clock with the bus clock also reaching its maximum frequency of 166MHz. However, as Beyond3D is able to confirm, the full clock is only available with WiFi being disabled, i.e. during network play the CPU clock is limited to 222MHz.

This has in fact some consequences for PSP game development. Game titles with network play could effectively be either limited to using 222MHz only during single player mode, or to using a downgraded engine and assets for multiplayer mode, which could complicate the development process. Meanwhile single player-only titles like God of War can take full advantage of the speed boost.

As to why the policy was enacted we can only speculate that the decision has been taken to preserve battery life. Judging from the previous precedents with regard to the clock cap, we believe that this limitation will be removed later in the PSP cycle, thus finally giving the developers free reign.

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