I try to do a UEFI boot from a USB Stick.
Somehow I deleted accidentally the UEFI Entry in the BIOS Setup.
First step to Reset to defaults - but I had no luck to get it back.
So I did a BIOS Upgrade from A15 to BIOS Version A17 (https://downloads.dell.com/FOLDER05046853M/1/T3600A17.exe)
But still no more "UEFI Boot" Menu
How do I select now a Boot Device for example a Bootable USB Drive?
Make sure that you connect the USB stick onto a general USB 2.0 port but not 3.0.
If you confirm USB stick connect to the right port but still can't boot, try downgrade to A13 or below. If it works this way, I'll further tell you the trick ^^
Try first. The problem you're facing now may or may not related to BIOS version. But if A13 really works, DO NOT upgrade back to A17. I'll tell you the trick then.
so I am back on A13 (https://downloads.dell.com/FOLDER02190235M/1/T3600A13.exe)
Nothing changed - still no UEFI USB Boot device - just Lagacy Mode Boot.
So maybe you little secrect will be the solution?
It was a long story.
My T5600 suffer from more or less the same problem as yours before. Sometimes UEFI boot device no show, and cannot even add manually. Sometimes USB boot device detected but cannot boot (only a black screen) no matter by BIOS or UEFI mode. Really ignoring...
Until last Saturday I tried all possible BIOS version from A05 to A18, then finally located a change on A14 not only affect read request size on PCIe but also lead to USB boot problem as well. Details in this thread. After flash back to A13, everything's fine now.
Then I noticed to your post and checked that BIOS A14 for T3600 contains exactly the same enhancements. That's why I recommended a BIOS downgrade for you at the very beginning.