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Author Topic: UEFI-bootable DOS substitute  (Read 977 times)

Offline TopNotch

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UEFI-bootable DOS substitute
« on: November 29, 2016, 08:45:14 AM »
The company I work for has a customer that wants what amounts to a UEFI-bootable DOS substitute. So I cobbled together GRUB2 and corepure64. It boots just fine, but I can't figure out how to change the screen resolution of the text. The customer wants 25x80 (DOS) character resolution, and it boots up in a higher resolution. Any GRUB2 parameters for changing resolution in grub.cfg are ignored. Do any of you know how to change resolution for UEFI boot?
The more complex the mind, the greater the need for the simplicity of play.

Offline nitram

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Re: UEFI-bootable DOS substitute
« Reply #1 on: November 29, 2016, 10:53:52 AM »
Hi TopNotch. The 'text' bootcode provides an ~ 25x80 TTY. Could setup two Grub boot options, one for "graphic" mode, the other TTY 'text' to simulate DOS. Or use the 'multivt' bootcode, boot into regular graphics, when time for DOS type work press Ctrl-Alt-F# to work from TTY. Or if running Xorg in graphic mode use the xrandr command (eg xrandr -s 640x480) to set resolution. Test various resolutions, then create an ~/.X.d/ entry to load the desired resolution at boot.

Offline TopNotch

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Re: UEFI-bootable DOS substitute
« Reply #2 on: November 29, 2016, 11:20:31 AM »
It is my understanding that in UEFI mode, graphics resolutions are set using the Graphics Output Protocol (GOP), and not VESA commands. So if parameters such as "GRUB_GFXPAYLOAD_LINUX=640x480x16" or "vga=0x769" or even the "text" parameter use VESA commands, they will be ignored in UEFI mode. So the problem is, how to get GRUB2 to use GOP.
« Last Edit: November 29, 2016, 11:29:02 AM by TopNotch »
The more complex the mind, the greater the need for the simplicity of play.

Offline Juanito

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Re: UEFI-bootable DOS substitute
« Reply #3 on: November 29, 2016, 08:21:22 PM »

Offline TopNotch

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Re: UEFI-bootable DOS substitute
« Reply #4 on: November 30, 2016, 11:48:37 AM »
Did you take a look at the example here:

http://forum.tinycorelinux.net/index.php/topic,19364.msg119228.html#msg119228

I already have it booting in UEFI mode, so that doesn't apply.
The more complex the mind, the greater the need for the simplicity of play.

Offline Juanito

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Re: UEFI-bootable DOS substitute
« Reply #5 on: November 30, 2016, 07:02:50 PM »
Yes, but I thought you wanted to to see how to change the resolution