We just ran into and issue, more of nuisance really, with our PXE point downloading the x64 boot wim. This is a nuisance because we associate the x86 boot image with all of our task sequences and and if PXE downloads the x64 boot image, it then has to download the x86 image after the task sequence is selected and the deployment engineer will have to click finish for the computer to reboot and continue executing the task sequence.
As it turns out, what we were seeing was expected behavior. The way ConfigMgr PXE works is that (as long as it passes the architecture test) it downloads the boot wim that is associated with the last task sequence that has been advertised to that collection. In this case it was an x64 boot wim associated to a task sequence, that had evaded us in our QA check.
How the solution was found was by checking the status messages for the SMS_PXE_SERVICE_POINT that was having issues. While reviewing those messages on of our engineers (Mark) noticed that following message:
"The SMS PXE Service Point instructed the device to boot to the bootimage <x64BootImage> based on advertisement <AdvertisementID>."
He searched for that advertisement and the Task Sequence that was assigned to it and that task sequence was associated with the x64 bootimage. Once that task sequence was associated with the x86 image that PXE service point now selected the x86 as the default bootimage to load for client requests.
We push both x64 and x86 images with the same task sequence, the choice is made which bit level OS to push in the task sequence (soon to be pre-executin hta). So we always want the x86 bootimage to download for all task sequences since it will download on all computers.