[syslinux] PXE linux starts slowly

[Gerrit Binnenmars]

Hello,
 
On our system (embedded Intel based board acting as server, compact pci switch, number of embedded Intel based client boards) it sometimes (guess is one of 25 starts) occurs that some client boards start very slowly.
The client has received the pxelinux.0 file and now starts asking for a pxe configuration file. The server sends TFTP error indicating the file is not present (we only have a default file) but pxelinux seems not to see this response and retries the request several times with the same filename. (I checked that the message is on the switch port with a port mirroring function).
Eventually after 20 minutes the board resets and than it starts without any problem.
We have seen this with syslinux 4.00 and 4.02.
 
Is this problem known?
How can we investigate it further?
So far we were not able to rebuild pxelinux.0 on a RedHat4 system to add debug info (additional printf), the file gets too large for prepcore. Is it possible to post the output of the original make process to check any differences ( I have gcc 4.2.3 and nasm 2.09) or at least the version of the tooling needed?
(I am very interested in the thread How to compile syslinux 4.03)
In the past, version 3.70 of syslinux, I was able to build pxelinux.0.
 
With regards,
 
Gerrit Binnenmars