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I am trying to install FreeBSD in legacy mode (BIOS) on a UEFI system, since I have an Intel Iris Graphics 6100, which is from Broadwell series and is not supported yet by the intel driver, so I want to be able to use the vesa driver - which is not supported by UEFI.

I already have 2 Linux systems installed, on a GPT disk, and I started the FreeBSD live CD in legacy mode, believing (stupidly, I must say), that it would install in legacy mode, and that I would be able to boot from it in legacy mode.

So, is there a way to boot from FreeBSD in legacy mode, on a GPT disk, or to have support for Broadwell graphics card in FreeBSD while using UEFI?

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    Ok, @GAD3R 's answer is great, I did not have the opportunity to test it sadly. In the mean time, there was progress with the FreeBSD graphics stack, and according to this, my graphics card is supported in 12-CURRENT (testing). I'll try this way, which looks more promising for future evolutions :) – cocosushi Nov 6 '17 at 19:56
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Yes you can install FreeBSD in Legacy mode on GPT disk.

You can achieve it by creating a small partition called bios_grub (important) before installing FreeBSD , this partition is required to successfully install Grub on the Master-Boot-Record.

Some newer systems use the GUID Partition Table (GPT) format. This was specified as part of the Extensible Firmware Interface (EFI), but it can also be used on BIOS platforms if system software supports it; for example, GRUB and GNU/Linux can be used in this configuration. With this format, it is possible to reserve a whole partition for GRUB, called the BIOS Boot Partition. GRUB can then be embedded into that partition without the risk of being overwritten by other software and without being contained in a filesystem which might move its blocks around.

When creating a BIOS Boot Partition on a GPT system, you should make sure that it is at least 31 KiB in size. (GPT-formatted disks are not usually particularly small, so we recommend that you make it larger than the bare minimum, such as 1 MiB, to allow plenty of room for growth.) You must also make sure that it has the proper partition type. Using GNU Parted, you can set this using a command such as the following:

parted /dev/disk set partition-number bios_grub on

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