Recently we saw pxebooting hanging randomly, without any error at all.

The pxeboot process simply stopped, and was hanging forever.

After long time looking for the error together with the hardware supplier and Microsoft, the error was finally found.

The server we were testing have 40 physical CPU’s and with hyper threading enabled the number is 80 logical cpu’s.

This caused the random error as 64 cpu’s is the max supported number .

To solve this there is 2 options:

  1. Disable hyper threading
  2. Install this KB hotfix at your boot image. http://support.microsoft.com/kb/2529956

Procedure to implement the fix:

Dism /get-wiminfo /wimfile:<path>\TempBootImageMount\winpe.wim

Dism /mount-wim /wimfile: <path>\TempBootImageMount\winpe.wim /index:1 /mountdir: <path>\TempBootImageMount\Mount

Dism /image: <path>\TempBootImageMount\Mount  /add-package /packagepath: <path>\TempBootImageMount\Windows6.1-KB2529956-x64.msu

Dism /unmount-wim /mountdir: <path>\TempBootImageMount\Mount /commit