I've been using the old pxelinux.0 version 4.06 for a while now and it works fine:
CLIENT MAC ADDR: 00 50 56 33 07 01 GUID: 564DCD75-3B1C-88C8-F497-7F51CDED582E
CLIENT IP: 192.168.51.7 MASK: 255.255.255.0 DHCP IP: 192.168.51.10
PXELINUX 4.06 2012-10-23 Copyright (C) 1994-2012 H. Peter Anvin et al
!PXE entry point found (we hope) at 9E8E:0106 via plan A
UNDI code segment at 9E8E len 0BD2
UNDI data segment at 98F8 len 5960
Getting cached packet 01 02 03
My IP address seems to be C0A83307 192.168.51.7
ip=192.168.51.7:192.168.51.10:192.168.3.2:255.255.255.0
BOOTIF=01-00-50-56-33-07-01
SYSUUID=564dcd75-3b1c-88c8-f497-7f51cded582e
TFTP prefix:
Trying to load: pxelinux.cfg/01-00-50-56-33-07-01 ok
early console in extract_kernel
input_data: 0x00000000019f03b4
input_len: 0x00000000003da3dc
output: 0x0000000001000000
output_len: 0x0000000000db8910
kernel_total_size: 0x0000000000a9c000
Decompressing Linux... Parsing ELF... done.
Booting the kernel.
[ 0.494266] intel_powerclamp: CPU does not support MWAIT
Booting Core 8.0
Running Linux Kernel 4.8.17-tinycore64.
Checking boot options... Done.
Starting udev daemon for hotplug support... Done.
Skipping compressed swap in ram as requested from the boot command line.
Scanning hard disk partitions to create /etc/fstab
Setting Language to en_US.UTF-8 Done.
Setting hostname to web-vm Done.
syslog started.
klog started.
glibc_gconv.tcz: OK
mylocale-en_US.UTF-8.tcz: OK
...
As I'm trying to update the various parts of my systems I'm trying to migrate to pxelinux 6.03 in the syslinux extension. The problem is that it hangs after it displays the first line showing the version (so I know that part loaded OK). I read that I have to have ldlinux.c32 in the TFTP root, but it doesn't seem to get that far. I'm using busybox udpsvd for tftp so its logging leaves something to be desired.