I've got a problem with Slackware 14.2 on my new hardware:

- ASUS Z170-A mainboard with newest BIOS
- Intel Core i7-6700K
- 32 GB DDR4-RAM
- Samsung SSD 850 Pro

Before installation I disabled UEFI and Secure Boot. I could install Slackware without problems and I could boot the installation at first but the second boot ended up with a couple of error messages. They run quickly over the screen and I could only read one of them:

...[drm:gen8_irq_handler [i915]] *ERROR* Fault errors on pipe A

Then, I deleted the GPT partition table and re-installed Slackware. And again, at first I could boot it successfully but at the second boot I got those errors.

Next, I enabled UEFI and installed Slackware as described in the README_UEFI.TXT file. And now at the first boot I got the errors mentioned above.

Hi, welcome to LQ!

When UEFI was enabled did you make it sure that Secure Boot was turned Off?

Did you try Installing with UEFI enabled?

malekmustaq, you're right. In order to disable Secure Boot I looked for a description on the web. I found one which says that I should just delete the PK Management key within the Secure Boot section and leave everything else untouched. Afterwards I rebooted and checked the configuration for Secure Boot. But I don't remember the value displayed for the Secure Boot sate (Disabled, Enabled or something else).

Now, after your hint I checked it again: Secure Boot was enabled.

I deleted all Secure Boot Keys and did a new install. When starting cgdisk for partitioning I got a warning: "Non-GPT or damaged disk detected! ..." After partitioning I checked it with gdisk and got no error. I went on to install Slackware. And at the first boot I got those errors again (see above).

Next, I checked the Secure Boot settings again:
Secure Boot state: Disabled
Platform Key (PK) state: Unloaded
OS Type: Other OS
(UEFI was enabled, of course.)

I did another install with UEFI (and Secure Boot) disabled. But at the first boot I got those errors again (see above).

I'd suggest booting with Slackware Live CD or at least some Live distro to scan logs for the full error picture. Since Slackware tends to NOT auto add things to the kernel load process it seems quite odd that it would boot OK once and only after generate any serious errors. That said, unless you have drives exceeding 2.2TB (yes that is a "T") or require many primary partitions** there is no perceivable value to most users in using UEFI/GPT and MBR is far less finicky and troublesome. Maybe consider "Legacy".

**NOTE - single systems using MBR have successfully installed 25 operating systems on the same machine so "many" really does mean "many"

I am new to this EFL stuff. Slackware installed with elilo. Elilo in combination with refind worked great for me. I managed to dual boot with Windows 10 without changing anything in bios. I just used bios to boot from my slackware dvd as I troubleshooted trying to understand what was going on. I guess I don't have secure boot?! I had to reinstall windows 10 boot in my efi partition using the windows 10 dvd command prompt. I used the refind found in slackbuilds and it picks up and manages the operating systems automatically and perfectly. I used efibootmanager to change the order of booting to refind and everything works great. I don't know if this helps at all but this is my own experience with EFL.

I've booted with Slackware64 Live v1.1.2 (actual -current). My mainboard is equipped with an Intel onboard graphics. I connected it to a monitor while a second monitor was connected to an AMD graphics card (Radeon R9 270). This second monitor became black (sleep mode) but the first one (Intel) displayed lots of vertical lines in all colors. Unfortunately, I couldn't switch to a text console.

Meanwhile, I could install Debian (using the live version 8.5.0 + non-free firmware). I disabled UEFI. So, now I've got some log files from Debian.

How can I find the relevant infos to find out what Slackware needs?

Did you run xorgsetup? Do you have the x86_64 drivers for them installed? dmesg maybe?

No, I didn't run xorgsetup. I just did a default/full Slackware install and rebooted. After the first (successfully boot) I've started X with 'startx' and KDE came up.

Perhaps you could use smartctl to test your drive.

I may have done two dozens of installations on my machine with different combinations of hardware and BIOS settings (UEFI and Legacy). I tried not just my SSD but a conventional hard drive too. Both work fine with other distros in combination with that mainboard. So, they are not defective. I tried to alter the UEFI configuration (using the UEFI shell) as described at the end of the README_UEFI.TXT. Nothing helps.

The errors do occur at the first or second boot after installation at about seven seconds boot time (according to onscreen time counter).

And I made a custom USB boot stick (as offered during installation). Once again, at first I could boot from that stick but the second boot fails with the same errors.

Would a newer kernel help with this issue?
Would it be possible to install Slackware 14.2 stable as usual but install a newer kernel before first boot?

I have the same motherboard (Z170-A pro) and could install successfully slackware using legacy. But I used MBR on the SSD I boot from. On another HDD I use GPT without any problem.

I found the answer:
I simply had to disable the onboard graphics (Intel).