Booting process & memory layout.

Francois-Rene Rideau
Fri Mar 12 00:33:47 CET 2004

On Thu, Mar 11, 2004 at 08:11:06PM +0100, Oleg Gusev wrote:
> Can you do 'dd if=/dev/mem bs=4096 | od -A n -t x4' ?
You forgot to add 0xc0000000 to the address!
dd if=/dev/mem bs=4096 skip=$[0xc0000] | od -A n -t x4

> I can't unless i add 'skip=8'.
What is surprising is that you can access the skipped address at all.
What does the CPU map at this place?

> That was exactly my point. To preserve wince you need only 1MB+384K.
> And i have reverted your change locally ;) I reboot j820 very often,
> and the broken sound/light intensity settings are extremely annoying.
OK, now I see your point. Well, patch welcome!

> Second, IMO the 1kHz counter is some side effect of the hpcboot setup
> or linux init code.
At least it exists when hpcboot loads blob without linux
(that's how I discovered it, to begin with).

> Although the value at 5c080 is not "absolutely" constant,
What do you mean? That it is not hardwired but configured in software?

>> PS: I've just bought off eBay a unit with 32MB RAM...
> The picture!!! And you own us a memory autosizing patch :)
Well, we'll see that when I receive the unit :-)

> Now I have a new idea - what will happen if i will remove the ROM
> module on j820 running linux ? Will it be visible on some GPIO ?
Isn't there a hazard for the computer if you do it while the power is on?

[ François-René ÐVB Rideau | Reflection&Cybernethics | ]
[  TUNES project for a Free Reflective Computing System  |  ]
The hacker: someone who figured things out and made something cool happen.
	-- Alan Schmitt

More information about the Jornada820 mailing list