Before I make any system changes such a boot loader, I do test it on the VirtualBox… after creating an ebios file on the hda1, the system boots to gujin's stage 1, passes vga probe, detects 2 partitions ( sda1/2 ) and the screen turns black…. forever… I do not know if this is vesa issue, or it cannot access stage 2, or is sth wrong with the config file… is there a way to debug it? or what should I try next?
hda … not sda
If Gujin has displayed that it found 2 partitions, it has definitely loaded (and checksum'ed) all of its code so it is not a problem accessing stage 2.
On a real PC, it can happen that the screen switches to black when Gujin goes into a graphic mode - the reason is that Gujin selects the default video mode only based on the screen maximal horizontal and vertical resolutions, as reported by EDID (a protocol linking physical screen and video card by I2C bus), and the capabilities reported by the video BIOS.
Gujin do not look at the maximal refresh frequency reported by the screen, so it can happen that the resolution Gujin selects is valid for both the screen and the video BIOS, but the frequency is too high for the screen - and so the screen goes into a protection mode and switches to black.
It is most usual when using flat screen TV as monitor - those have very low maximal frequencies.
Gujin could check these conditions and try a lower resolution automatically, or use a special mode setting video BIOS function to request a special refresh frequency - but the second solution is said to have problem on some card (that code is disabled in other bootloaders).
Anyway that problem is relatively rare, and can be solved quickly by the user because the '+', '-' and '.' keys enables you to switch respectively to a higher/lower resolution, or go to text mode.
You problem is very likely a bug in VirtualBox video BIOS, once you are at the black screen step, try to press "tab" to see if there is an alternative video BIOS number with the same resolution which would work - if not try to press '-' to see if there is a lower resolution which will work. If the VirtualBox video BIOS crashes the virtual machine when that resolution is selected by Gujin, then you can press the control key alone from "power-up" to the line where Gujin displays "Control key pressed, force text mode" around the third line of the screen to not go into graphic mode at all.
Another test would be to disable the VESA linear (i.e. VESA 2) mode setting in Gujin menu, maybe VirtualBox video BIOS is more tested for VESA 1 compatibility.
It would be nice to know the result of these experiments…
Sorry, just to add:
> is there a way to debug it
You can generate a floppy image wich will send debugging messages to the serial port (you would redirect it to a file by VirtualBox setup) by typing in the Gujin source directory:
and the file dbgvideo_com1.144 is the image of a 1.44 Mb floppy you should be able to use to boot VirtualBox with.
thanks for the reply, -' / '+' change the resolution, TAB does nothing "visible", the screen is still black
regarding the EDID, I do not trust EDID - had to find workarounds for the EDID and latest X11 - several drivers / kernels are unable to query and process EDID the way they should….
GUJIN is unable to get EDID from the VirtualBox's driver - I would suggest to force for example a 16 or 256 color native VGA resolution, in case of failing the EDID request…. what do you think?
If I correctly understand, you no more have a problem of black screen once typing '-', so you can set the default graphic mode of Gujin at installation time.
'Tab' searches if there is another video mode with the same resolution and same number of colors to switch to, some video cards have same resolution but different refresh frequencies.
It is not possible to ignore EDID and select an acceptable video mode on most "wide" screens, it looks too bad - but if Gujin do not get an answer to an EDID query, it already defaults to 800x600 with maximum number of colors the video card BIOS can support. The video BIOS of VirtualBox for 800x600 32BPP is probably broken in your case.
At least some of the problems of Linux + EDID are due to Grub2 which bypass the real mode part of the Linux kernel; Grub2 asks the EDID after having switched to protected mode and put the table at a fixed address in memory. It works usually fine with Grub1.
The resolution changes - the size of the VirtualBox window changes - but the screen remains black - nothing visible - and I tried about 6-7 different resolutions
got it… partially…
Disabling the hardware virtualization ( SMP support etc ) VT-x/AMD-V it comes up in the default graphical mode fine…, I noticed also, it detect the drives/partitions much quicker - without virtualization
As I said already, you should try to disable the VESA 2 (VESA linear) support in Gujin, either at installation or starting in text mode and then ticking a box in Gujin menu (and enable writing to disk to store the setup).
To debug, you may log the screen debug to serial port, I am suspecting VirtualBox do not support correctly the "large" real mode with 4 Gb segments.
it is fine in all video modes, the intel/amd h/w virtualization mode needs to be disabled for gujin to function properly, it is good enough to test on single core, but on SMP enabled VirtualBox guest OSs, gujin will fail…
Well, Gujin works well on SMP PCs; if VirtualBox do not correctly simulate SMP PCs, it is not really Gujin's fault, don't you think?
But I can try to disable the support of VESA linear if Gujin detects VirtualBox - assuming that is the problem (Is Gujin working on VirtualBox with intel/amd h/w virtualization mode when VESA linear is disabled?).
Also, on VirtualBox with intel/amd h/w virtualization, what is the end of the line with processor type displayed at boot, after "on BIOS"?
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