Simply press s immediately after boot time (while RAM is counting up).

1. Boot: 1 PC Engines ALIX.2 v0.99
2. 640 KB Base Memory
3. 261120 KB Extended Memory
4.  
5. 01F0 Master 848A SanDisk SDCFB-1024
6. Phys C/H/S 1986/16/63 Log C/H/S 993/32/63
7.  
8. BIOS setup:
9.  
10. *9* 9600 baud (2) 19200 baud (3) 38400 baud (5) 57600 baud (1) 115200 baud
11. *C* CHS mode (L) LBA mode (W) HDD wait (V) HDD slave (U) UDMA enable
12. (M) MFGPT workaround
13. (P) late PCI init
14. *R* Serial console enable
15. (E) PXE boot enable
16. (X) Xmodem upload
17. (Q) Quit