Usually it takes a long time for PXE Boot during the downloading boot image file, you can change the registry settings to make it faster:
HKEY_LOCAL_MACHINE\Software\Microsoft\SMS\DP\RamDiskTFTPBlockSize
Type Reg_Dword
Value: 16384 Dec
((Recommend that you increase this setting in multiples (4096, 8192, 16384, and so on) and that you not set a value higher than 16384.))
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