If you have ever used operting system deployment with SCCM and not just SCCM, then you know that before installing full OS computer boot in Windows Preinstallation Environment (WinPE). This WinPE is usually called a boot image.
Let's get to the subject - when using SCCM with PXE, x64 or x86 boot image can be loaded. But what happens when computer is advertised with both x64 and x86 Task Sequences how do you control which boot image to load?
The answer is simple - with SCCM it is not possible to control which boot image is loaded. The SCCM loads the boot image for last deployed Task Sequence.
The consequence of this is, for example, that if you booted a x86 boot image then after choosing to deploy a x64 Task sequence the first thing would be to download a x64 boot image and reboot and only then execute the Task Sequence.
A possible solution for this could be to create a separate collections for x64 and x86 computers and only deploy appropriate Task Sequences. For new computers you would first have to import computer to the necessary collection.