LinuxQuestions.org - [SOLVED] Scrambled console text

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- - Scrambled console text - UEFI boot (https://www.linuxquestions.org/questions/slackware-14/scrambled-console-text-uefi-boot-4175479719/)

Scrambled console text - UEFI boot

Tried this recently on a new thin laptop that comes with UEFI and Windows 8. I made a bootable Slackware ISO image, processed it so it is USB bootable then wrote it to a USB stick as per instructions found in http://taper.alienbase.nl/mirrors/sl...nux/README.TXT, then tried booting in UEFI mode off the USB, Grub menu came up and I booted the non-kms option, unfortunately I got an unreadable console (and the penguins are badly mangled too)
Anyone had a similar issue?

One of your images (all the bits of words all over the place) is a classic problem of horizontal frequency. Every box is/was supposed to come up at 640x480x60hz initially and then you can set fancy settings if you want. I guess the fancy stuff is going wrong.

Isn't 1024x768 the regular resolution of UEFI framebuffer? That is what Windows 8 requires for its splash screen.

Some more hardware info is required for solving this issue.

m$ could have upped it to 1024x768 - I don't track m$. It's still no use to The OP That's a 4:3 resolution, and the screenshots are of a 16:9 monitor.

The screenshots make clear that the video is running at the wrong setting. Is there a vga= line in the boot sequence?

Quote:

Originally Posted by business_kid (Post 5041013)

m$ could have upped it to 1024x768 - I don't track m$

They do that since 2006 I think. Maybe we don't track MS, but PC hardware/firmware vendors surely do.

Quote:

Is there a vga= line in the boot sequence?

vga= doesn't apply, because it controls the VESA/VGA console driver, which is disabled on EFI systems.

What does the KMS boot option do?

Quote:

Originally Posted by jtsn (Post 5040721)

Some more hardware info is required for solving this issue.

Thanks for the feedback. It's an Acer Aspire V5-472 with Intel HD 4000 graphics and an i5 processor. It came with Windows 8 and UEFI.

Code:

00:00.0 Host bridge: Intel Corporation Ivy Bridge DRAM Controller (rev 09)

00:02.0 VGA compatible controller: Intel Corporation Ivy Bridge Graphics Controller (rev 09)

00:14.0 USB controller: Intel Corporation Panther Point USB xHCI Host Controller (rev 04)

00:16.0 Communication controller: Intel Corporation Panther Point MEI Controller #1 (rev 04)

00:1a.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #2 (rev 04)

00:1b.0 Audio device: Intel Corporation Panther Point High Definition Audio Controller (rev 04)

00:1c.0 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 1 (rev c4)

00:1c.1 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 2 (rev c4)

00:1c.2 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 3 (rev c4)

00:1d.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #1 (rev 04)

00:1f.0 ISA bridge: Intel Corporation Panther Point LPC Controller (rev 04)    

00:1f.2 SATA controller: Intel Corporation Panther Point 6 port SATA Controller [AHCI mode] (rev 04)

00:1f.3 SMBus: Intel Corporation Panther Point SMBus Controller (rev 04)                                                                                                

03:00.0 Network controller: Atheros Communications Inc. Device 0034 (rev 01)                                                                                            

04:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. Device 5287 (rev 01)

04:00.1 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 14)

Quote:

Originally Posted by volkerdi (Post 5041030)

What does the KMS boot option do?

KMS option starts up with a scrambled console then a black screen.

Try

Code:

video=efifb:off

together with the KMS option. Try ELILO. Or try doing a legacy boot, so you get a VGA text mode console.

The HD4000 is not a difficult card to drive. I have one here - no issues with or without uefi. I have slackware & fedora installed. The hd I removed had uefi & windows 8. Could it be the monitor?

Quote:

Originally Posted by jtsn (Post 5041149)

Try

Code:

video=efifb:off

together with the KMS option.

This option seems to turn off the console completely, with or without KMS, as soon as Grub loads the OS.

I installed Slackware by booting in legacy mode, this went smoothly as usual. At that point I set up elilo, grub2 and rEFInd in the EFI partition, rebooted and switched back to UEFI mode.
Grub2 and elilo booted into the scrambled console. However, booting via rEFInd either directly or by chainloading elilo (or grub2) worked, not really sure why. May be rEFInd somehow sets up the correct resolution and/or framebuffer?

It turns out rEFInd is using graphics mode by default, Grub2 and elilo are not during EFI boot. The Slackware EFI boot off the USB image runs in console mode.
When chainloading Grub2 or elilo off rEFInd they somehow kept the correct mode, otherwise they'd boot into a scrambled screen. I managed to EFI boot directly off Grub2 (without rEFInd) by setting the gfxmode, setting the gfxpayload to "keep" and switching to a gfx terminal. Also a font has to be loaded off the file system (not available on the Slack USB) otherwise you'll get an unreadable menu once you switch to the gfx terminal but booting would still work once you press enter on an item.

Code:

loadfont unicode.pf2

set gfxpayload=keep

set gfxmode=1024x768

terminal_output gfxterm

Marking this thread as solved.