Perhaps you could include a x64 version so we could confirm those assumptions?
It's not easy to make 64-bit version of WinSCP. We definitely aim for that, but it will take time.
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.
Perhaps you could include a x64 version so we could confirm those assumptions?
winscp.exe sftp://user@host/ /rawsettings TcpNoDelay=1 /log=session.log
iperf -s
iperf -c server.ip.address.here
[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.0 sec 850 MBytes 712 Mbits/sec
.