Quote:
Originally Posted by customelectronic
Why sony needed the extra Renesas one has me stumped. My curiosity is getting to me. This thing is seriously overkill in the way it is built -- the ARM processor has all the peripherals built in, but Sony still used external peripheral chips... that makes me wonder why.
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The Renesas chip is the "subcpu" mentioned in the subject of this thread. It is present in all models beginning from PRS-500 (and probably Librie). Sony uses it to handle the simple tasks of controlling keyboard, power, leds and touch screen. I guess this way the big and hungry ARM can spend most of the time sleeping on low power but when it needs some time for number crunching - such as rendering HTML - it doesn't need to bother about all the "small fish". I think it's also for this reason that Sony went back to using a dedicated SD/MS controller (Ricoh R5C807) after a short stint of relying on the built-in CPU ports in PRS600. Such extra hardware might increase the cost a bit but it seems it does help to save power.