HP DC7700 imaging is very slow - 3 hours for 1.5gb image via PXE

Netware v6.5 SP4 server with ZFD 7 SP1 + hot patch.

HP DC7700 takes over 3 hours to download a 1.5Gb image (via PXE)
Other model workstations download image in less than 1 hour on same infrastructure (cables switch ports etc)

Anyone got any ideas.

Had to apply the hot patch to get PXE imaging to work on the HP DC7700.