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mattd on October 2, 2011 at 4:37 pm said:
1) With no onboard data storage, how does the GPU go about starting the
boot process? Is there something hardcoded that allows it to mount and
read the SD card?
2) Was booting RasPi without NAND/NOR uniquely difficult, or is this common with ARM chips?
3) Any interfaces supported by the chip (e.g. audio input) that you could
not physically fit/be routed on the board?
4) PCB routing difficulties – are these common with similar SoCs or due to
the unique RasPi size?
5) Do both HDMI and composite outs work simultaneously or does one
have to be selected in software? (I’m guessing the composite video puts
out whatever’s sent via HDMI downscaled to 480i …)
Thanks for keeping us informed, this is such a great project!
Reply ↓
SteveH on October 3, 2011 at 4:22 pm said:
The GPU has a boot rom (i.e. hard coded into the chip) that understands
FAT16 and FAT32. This was originally included in the boot options to allow
easy demonstration of the devices (and to speed development as it only
requires the copying of files to a SD Card and not reprogramming
NAND / NOR).
Reply ↓
Gert on October 5, 2011 at 9:39 am said:
1/ As Steve H says: code in boot rom
2/ You need and SD card driver in bootrom
3/ We cut down on GPIO pins.
4/ These are common to most high density BGA package nowadays.
5/ Plan is to auto-detect HDMI and switch to composite if not present.
That code is not developed yet. I assume for composite we need
a ‘press key until you see a picture’ mode to go
trough all the world standards.