Some Useful Websites
1. The HP Computer Museum: comprehensive information on HP computers and peripherals of all types developed up to the mid 1990s.
2. The HP 9845 Project: Ansgar Kueckes' site dedicated to the HP 9845 technical workstation family. Includes much useful information relevant to series 300 including discussion of the LIF filing system. Source for HPDrive, HPDir and other useful software tools.
3. Bitsavers document archive: many scanned manuals covering HP 9000 series 300 hardware and software.
4. Bitsavers software archive: operating-systems, firmware and applications software for HP 9000 computers.
5. Hewlett Packard Archive: dedicated to collectors and curators of vintage Hewlett-Packard equipment, catalogues, HP Journals and other periodicals.
6. VintHPcom@groups.io: this group is about all kind of vintage HP computers build before about 1990 (except series 80).
7. Wikimedia Commons photo archive: excellent collection of more than 1000 photos by Thomas Schanz showing HP 9000 series computers. Many of the photos used on this site are taken from the Wikimedia Commons archive.