I've had a Z97 FTW since new and have single booted it the whole time. I want to dual boot and and so need to boot from USB to install on a second drive so I need to change the boot order.
If I try to get into the BIOS by pressing DELETE on boot I get a blinking cursor in the upper left of the screen and nothing further happens. If I don't press DELETE it boots normally, into GRUB and then Linux.
I've pressed the CMOS reset button, both on the back and on the motherboard. Neither seemed to change this behavior. I've held the button down for > 5 seconds and this also doesn't seem to change the behavior.
Any suggestions would be appreciated.
 

If I hit F7 it takes me to a screen with text that says this.
 
Version 2.15.1238. Copyright (C) 2013 American Megatrends. Inc.
BIOS Date: 10/09/2014 10>49:19: E977 187
 
It just sits there with this. I hit a bunch of keys, but that didn't seem to have any effect.

If I spam Esc during boot it has no effect; it just boots normally to the Grub menu.
If I spam Esc after F7 it has no effect. It just sits at the BIOS copyright notice text (as above.)

I get a flashing cursor in the upper left of the screen and 'A2' in the lower right of the screen.

I replaced the cmos battery with a new one but nothing has changed

Now when I boot the clock starts off wrong.
$ date
Wed Aug 26 02:42:18 PM PDT 2020
 
It should say this:
$ date
Sun Sep 6 02:16:04 PM PDT 2020
 
I'm assuming this is due to the CMOS being reset. 

I can boot to SATA now. I still can't get into the BIOS though.

If I mash the DELETE key on boot all I get is the blinking cursor in the upper left.
If I hit F7 I get to the BIOS copyright screen (reproduced above).
I've tried two keyboards with multiple different USB ports, some USB 2, some USB 3.
 
 

When I couldn't boot to SATA yesterday I went out and bought a new battery, so that's brand new now.
I've tried booting with no drives and get the flashing cursor in the upper right. Normally it just sits there.
If I've just removed and replaced the battery though (or hit the cmos reset button) I've found I can hit F1 or F12 and the following message shows up for about a second then it goes back to the flashing cursor.
 
CMOS checksum error
Press F1 Skip. F12 Enter Setup
Version 2.15.1238. Copyright (C) 2013 American Megatrends. Inc.
BIOS Date: 10/09/2014 10>49:19: E977 187
Press <DEL> or <F2> to enter setup.
 
This message disappears very quickly. The only reason I know what it is is that I managed to take a picture as I hit F12.
I've tried hitting DEL and F2 before hitting F1 or F12 and neither does anything. I've tried hitting them very quickly after hitting F1 or F12 and it seems to have no effect. I get back to the blinking cursor and no key has any further effect that I can see.

Yeah, I've tried the second bios and it has the same behavior. If I hit F2 or DEL it goes to the blinking cursor and sits there.
 

Normally I have a single Samsung 850 EVO 500GB SSD running Manjaro, with Grub 2.04 as the bootloader. (When I'm booting without drives as per some of the steps above, I of course have nothing.)

jmacc
When I couldn't boot to SATA yesterday I went out and bought a new battery, so that's brand new now.
I've tried booting with no drives and get the flashing cursor in the upper right. Normally it just sits there.
If I've just removed and replaced the battery though (or hit the cmos reset button) I've found I can hit F1 or F12 and the following message shows up for about a second then it goes back to the flashing cursor.
 
CMOS checksum error
Press F1 Skip. F12 Enter Setup
Version 2.15.1238. Copyright (C) 2013 American Megatrends. Inc.
BIOS Date: 10/09/2014 10>49:19: E977 187
Press <DEL> or <F2> to enter setup.
 
This message disappears very quickly. The only reason I know what it is is that I managed to take a picture as I hit F12.
I've tried hitting DEL and F2 before hitting F1 or F12 and neither does anything. I've tried hitting them very quickly after hitting F1 or F12 and it seems to have no effect. I get back to the blinking cursor and no key has any further effect that I can see.

Okay new CMOS battery. Have you done a complete BIOS reset? By this I mean, remove power completely. Remove the CMOS battery, press and hold the CMOS reset for 30 seconds. Let the system set for at least 5 minutes with no power, and no battery. Reinstall the battery and power and see if you can boot into the BIOS with no drives attached.

jmacc
I haven't done 30 seconds; I've done 5 seconds but with power enabled. So just to clarify, 30 seconds with no power and no battery?

Oh yeah...if you've not actually done a complete BIOS reset, I'd try that. Hold the CMOS button for 30 seconds with no battery and no power. Let the system set for at least 5 minutes prior to reinstalling the battery and applying power.

 I figured it out!!
 
The problem was I was using a 4K monitor and apparently the BIOS has no idea what to do with that so it just displays a blinking cursor! If I use a 1920x1080 pos monitor the BIOS comes right up.
 
Haha I hate to think how many hours I spent messing with this.

👍