[ECOS] i386 Ram Access

Iztok Zupet iztok.zupet@vsr.si
Thu Nov 7 06:09:00 GMT 2002

On Thursday 07 November 2002 13:34, Erdem Guven wrote:
> Hi,
> I have a 386 pc standard motherboard. I had build a
> redboot rom image by ecos conf. gui:
> - Build > Temp. > i386, redboot
> - File > Import > redboot_ROM.ecm
> - "validate ram address..." is disabled
> then I wrote to a eprom and pluged it to place of
> bios. It's working good but I can't access ( dump,
> mfill, load ) ram over 1MB.
> Then I changed configuration's "Startup type" to
> floppy, build, copy to floppy, pluged bios back. It's
> working and also I can access ram over 1MB.
> What's the difference between these two codes?
> Why I can't access ram over 1MB?

The fact is that the BIOS initializes the motherboard chipset (memory 
controller in this particular case) completely, whilst RedBoot/eCos ROM 
startup routine initializes only the video, other common PC HW is initialized 
by the drivers.

According to my information, the project of replacing the PC BIOS by redboot 
has been started and brought to the current stage, but not developed further.

The ROM startup code for the eCos/RedBoot can be found in  
packages/hal/i386/pc/current/src/romboot.S assembly source, if You wish You 
can add the memory controller initialization inthere, just before the video.


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