Then I started flashing twin_test.bit into my boards and I've found that outside of virtual box it takes a lot less to flash a FPGA.
user@t5570:~$ time sudo ./xc3sprog -c cm1 -p 3 -Ixc6lx150.bit twin_test.bit
XC3SPROG (c) 2004-2011 xc3sprog project $Rev: 674 $ OS: Linux
Free software: If you contribute nothing, expect nothing!
Feedback on success/failure/enhancement requests:
http://sourceforge.net/mail/?group_id=170565
Check Sourceforge for updates:
http://sourceforge.net/projects/xc3sprog/develop
Using Libftdi,
DNA is 0x390dc1e841c73bf1
JEDEC: 20 20 0x18 0x00
Found Numonyx Device, Device ID 0x2018
256 bytes/page, 65536 pages = 16777216 bytes total
Verify: Success!
real 2m50.569s
user 0m4.340s
sys 0m10.517s
Less than 3 minutes per FPGA.
spiccioli.
Doing the direct programming of the FPGA is fast but won't stay when you power cycle. Loading ointo the SPI Flash takes longer but is there every time you power up the board.