You just a need a minimal system with a 386 processor and 8MB of RAM. HAL91 comes along with harddisk and CD-ROM support but it runs directly from
floppy out of a RAM disk.
A special feature of HAL91 is the included minimal support for NE2000 compliant network hardware and the ability to establish a PPP connection over a null
modem cable (via the ppp-nullmodem script). From Linux Gazette.
November 4, 2000