Greetings,
I'm no Geodeexpert, but perhaps I can help.
Typically at powerup, the adress space at ffff0000 - ffffffff is mapped to f0000:0000 (top of real mode memory at 1M). The CPU will start up at f0000:fff0.
The practical upshot is that the end of your romimage should be line up at ffffffff to get the power on jmp vector in the right place.
G'day, sjames
Happy New Year LinuxBIOS
Quoting Adam Bezanson bezanson@netaudiotech.com:
Hi guys,
I've finally built linuxbios for my SC1200 based board. I've written my own flash programming utility so I can program the "romimage" file produced into my flash part from Linux command line. This all seems to work fine. On my board, I have the ability (with a jumper) to direct the ROMCS# signal to one of 3 chips on the board. One is a Disk on Chip which currently has a DOS filesystem on it, one is a 2Mbit flash chip which has the original Insyde BIOS, and the 3rd is a 16Mbit flash part soldered on the board where I'm trying to put linuxbios.
This 3rd chip is at 0xffe00000 - 0xffffffff, in order to enable this addressing I must hit bit 2 in F0 offset 0x52 to enable the Upper ROM size based on the ROM Mask at F0 offset 0x6e. This isn't enabled by default so I think as the chip comes up only 0xfffc0000 - 0xffffffff is visible. I'm not 100% sure, but I assume as the chip comes up it starts trying to fetch instructions from 0xfffc0000, is this true?
My question is, where should I program the "romimage" file that comes out of the build process? It would seem to me that the linuxbios.rom part would have to start at 0xfffc0000.
Other notes: I've set up my PMR and MCR registers correctly for my target. I figured them out by hand and then verified their values when I run with the Insyde BIOS. So I'm 100% sure the values I'm using are correct for my target.
I've set the SCx200_DOCCS_BASE to 0xffe00000 for the moment and the CTRL to 0x070007ff I'm not sure if the BASE value is correct due to the questions I pose above.
All of my efforts have resulted in nothing happening at startup. Nothing out of the serial port nor are the Port 80 codes moving after the board is reset.
Any ideas/help would be appreciated.
Thanks and have a happy new year.
Adam
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