scp timeout on dual-core processor

["Harig, Mark" <maharig at idirect dot net>]

The Cygwin version of the openssh utility program, 'scp', appears to
have a defect that prevents
it from copying files above a certain size, when 'scp' is running on
computers with Intel 
dual-core processors.

Here is the information that I have gathered so far:

1. ssh from the client machine (which has the dual-core processor)
connects without error, and
   the connection is stable.  

2. scp is able to copy small binary or text files from the ssh server to
the client computer
   without any timeout errors.  Examples:

   $ scp ssh_server:/bin/ls .
   ls                                            100%   66KB  66.1KB/s
00:00    

   $ scp ssh_server:/bin/date .
   date                                          100%   38KB  37.7KB/s
00:00    

3. scp is unable to copy larger binary files from the ssh server to the
client computer.
   Examples:

   $ scp ssh_server:/usr/bin/gcc .
   gcc                                             0%    0     0.0KB/s
--:-- ETA
   Disconnecting: Timeout, server not responding.
   lost connection

   $ scp -o ServerAliveCountMax=1500 -o ServerAliveInterval=20
ssh_server:/usr/bin/gcc .
   gcc                                            73%   64KB   7.8KB/s -
stalled -
   Disconnecting: Timeout, server not responding.
   lost connection

I repeated the above tests using Cygwin's previous version of openssh,
4.3p2-2, the current
version of openssh, 4.3p2-3, and the experimental version of openssh,
4.3p2-4.

In the examples above, the string 'ssh_server' was replaced by the IP
address of the Linux server
that is running the ssh service.  The Linux server is running
openssh-3.6.1p2.

The Cygwin client scp was installed for the first time last week, with
the Cygwin setup.exe
defaults selected for a base installation.  Other utility programs that
were installed using
'setup.exe' are 'openssh/openssl', 'vim', and 'rxvt'.  Cygwin is
installed on a computer
running Windows XP.  I have installed the same version of
Cygwin/openssh/etc. on two more
computers with dual-core CPUs.  Both additional computers have the same
problem.

I have repeated the commands above without any errors on computers
running Windows 2000,
2003, and XP.  All computers are connected to the same network.  None of
the computers on
which the above commands ran successfully are using dual-core CPUs.

Using the standalone program 'WinSCP', all files listed above can be
copied from the server
to the client computer without any errors.

Has this problem been addressed previously?  Is it a known problem with
Windows XP running on
Intel dual-core processors?  Or, does anyone know whether it is a
problem with Cygwin running on
Windows XP on dual-core processors?

I have attached several files to provide more information:

   1. The output from the command 'cygcheck -s -v -r' (i.e.,
cygcheck.txt)
   2. A successful copy command using 'scp' with the option '-vvv'.
   3. An unsuccessful copy command using 'scp' with the option '-vvv'.

If you have any ideas about what might be causing this problem; any
ideas about how I can fix it,
work around it, or trouble-shoot it; or would like more information
about the environment that
could help diagnose it, please let me know.

Attachment: cygcheck.txt
Description: cygcheck.txt

Attachment: scp_ls.txt
Description: scp_ls.txt

Attachment: scp_gcc.txt
Description: scp_gcc.txt

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