Atempting to run the Yahallo exploit on a Surface1 with seems to result in a runtime error.

[Awe7]

Clearing eMMC amd Bare Metal Recovery

[Awe7]

[WiiNewU]

I have the same issue, its likely due to my surface having such an early release of the firmware (UEFI) installed that yahallo does not recognize it.

At this moment you should have seen something on the screen... 
Your firmware (gST): DemkS EFI Sep 10 2012 23:23:31, 0x0

Matching device
At this moment you should have seen something on the screen...
Yahallo - Tegra 3/4 Secure Boot Unlock Utility

[ERROR] Failed to find the device. It is probably not supported yet 
Your firmware (gST): DemkS EFI Sep 10 2012 23:23:31, 0x0 
!!! PLEASE RESET YOUR DEVICE MANUALLY USING THE POWER BUTTON !!! 
!!! PLEASE RESET YOUR DEVICE MANUALLY USING THE POWER BUTTON !!! 
!!! PLEASE RESET YOUR DEVICE MANUALLY USING THE POWER BUTTON !!!

I am just not sure on how to update the firmware only without updating my Windows RT install, mainly I have a very early version of Windows RT and the technical preview of Office 2013 that I want to dump / do not want to lose.