The kernel that comes with slackware 14.1 (3.10.17) is too large once USB support is added, so it can't boot Linux on 1MB devices. I used instead 3.4.106. According to https://www.kernel.org/ it is an long-term supported version. Whatever that means.
Steps to install:
- Download Slackware 14.1 DVD.
- Download latest Knoppix DVD.
- Install Slackware 32-bit in VirtualBox, A, AP, D, K, L, N disk sets. sda1 as swap (64MB), sda2 as EXT3.
- Check that all boots OK.
- Change securetty and inittab to add a serial port login
- Configure serial support on pipe in Virtual Box config and reboot
- Test the serial login works from another virtual machine running Knoppix, connected to the same serial port pipe (Knoppix comes with minicom).
- Replace hwclock line in startup scripts as found in previous slackware instructions
- Remove stuff about mime and gtk from startup scripts, just wastes time and resource during boot
- Download kernel for 3.4.106 from kernel.org
- Change timex.h file to adjust PIT_TICK_RATE for bifferboard
- Compile bifferboard kernel using the configuration below.
- Install the kernel modules with make modules_install
- Flash kernel to bifferboard
- Set kernel command line console=uart,io,0x3f8 rootfs=/dev/sda2 rootwait
It is working, however seems to use more RAM than Slackware 13.37. Probably worth finding a lighter shell than bash, as bash seems to use 4MB when running.