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Subject: Re: Open hardware for RockBox

Re: Open hardware for RockBox

From: B <>
Date: Fri, 25 Feb 2011 20:14:15 -0500

EPI --> External peripheral interface.

I believe the EPI on the chip I am planning building a development board
around runs at 50 MHz for SDRAM. The RAM is mapped into the CPU's memory map
higher number than the internal memory.

The internal SRAM is 96 KB or 64 KB depending on the device.

It can address up to 64 MB of SDRAM, but I think I am unlikely to have more
than 16 MB (8 or 16 are the most probable).

I take your point on the docs :-) I am much more a hardware than a software
person. This player isn't really going to be portable, and I think the
initial implementation from me will just be a few free codecs like FLAC that
are important to me, but I'd like to make sure the hardware could support
this excellent project.

On Fri, Feb 25, 2011 at 4:59 PM, Michael Sparmann <> wrote:

> > My question is what sort of hardware could you get away with. For
> > instance what if you had a bare ARM core and some SDRAM over a EPI
> > interface? Or what if you had just a tiny < 100 kB SRAM built into the
> core?
> Currently the absolute minimum seems to be in the region of ~2MB of RAM.
> If you want full functionality, you should consider taking 8MB or more.
> Having fast in-core RAM is of course always nice, but only having
> external RAM won't hurt much if the interface to it is reasonably fast.
> I have absolutely no idea what EPI is, but the external memory will need
> to be mapped into the CPU's address space, so most SoCs will probably
> need a RAM with a mobile SDRAM or mDDR interface.
> > Presumably all of these SoC use different drivers for the user
> > interface, the porting process must be quite lengthy...
> But, as you usually have documentation for that hardware, far less
> lengthy than the porting process to devices that need to be reverse
> engineered.
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Received on 2011-02-26

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