How to boot to USB in legacy boot mode?

[RoflWaffles02]

I have an old Dell Optiplex 780 that I am trying to turn into a Steam Machine.  The latest version of the bios does not support UEFI Boot mode.  Is there a way to install in legacy mode?

[TheCherryKing]

1 minute ago, RoflWaffles02 said:

I have an old Dell Optiplex 780 that I am trying to turn into a Steam Machine.  The latest version of the bios does not support UEFI Boot mode.  Is there a way to install in legacy mode?

Does steam OS even support Legacy boot mode?

[RoflWaffles02]

Just now, TheCherryKing said:

Does steam OS even support Legacy boot mode?

I don't think so, I was wondering if there was a work around

[TheCherryKing]

2 minutes ago, RoflWaffles02 said:

I don't think so, I was wondering if there was a work around

That is something to look into. If steam supports Legacy Mode create a bootable USB with a Master Boot Record file system instead of GUID Partition Table.

[RoflWaffles02]

1 minute ago, TheCherryKing said:

That is something to look into. If steam supports Legacy Mode create a bootable USB with a Master Boot Record file system instead of GUID Partition Table.

I was thinking I could use rufus to create an ms dos startup disk and run setup from there

[Master Disaster]

Steam OS should support both UEFI & Legacy mode as long as you're running the latest Brewmaster build. Steam OS always supported Legacy mode and Valve simply ported UEFI support over from a fork when they transitioned from Debian 7 to Debian 8 as the base.

 

Even the official requirements say UEFI BIOS (Recommended)

 

EDIT

 

OK so according to Valve themselves you must download and burn Brewmaster as an ISO for Legacy boot support, get the ISO from here

 

FYI Steam OS using using Kernel 3.18LTS as its base so if your running any hardware thats even remotely new the chances of it working with SteamOS are tiny. Its much simpler to install Ubuntu then run Steam in big picture mode over the top.