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Subject: Testing needed: Zero-wait boost for Coldfire - FS#9797

Testing needed: Zero-wait boost for Coldfire - FS#9797

From: Björn Stenberg <>
Date: Tue, 13 Jan 2009 21:45:10 +0100

Currently, boosting on coldfire involves waiting for PLL lock which can take as much as 10ms.

This patch changes the boosting to just toggle the clock divider and not change the PLL frequency, and thus not having to wait for it to stabilize. This makes the boost near instantaneous.

The MCU5249 docs can be interpreted to say you're not supposed to do this, but they are not conclusive. My limited testing showed no side effects so far.

In order to get clean clock dividers, the patch also changes the operating frequencies from 124/45 MHz to 112/24 MHz. The "default" (idle) frequency is unmodified in this patch and still uses PLL bypass, but is used so rarely it shouldn't have much impact.

Zero-wait boost opens up possibilities for more efficient cpu management in Rockbox. Coldfire is the only platform where we are not sure this is possible.

Ideally, someone who uses a coldfire player (Iriver or iAudio) as their daily player should run this patch and see if any side effects pop up.

If you would like to test this but can't build it, tell me and I'll build it for you.

Received on 2009-01-13

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