We’ve had a couple of mentions of the Holborn 9100 before, mainly because of the striking look.
But here’s a site - Technisch Museum (in Dutch) which includes much technology history including three pages on Holborn and their machines. Images in this post are from that site: please visit and explore.
Here are some deep links:
Holborn computers (Overview and history, photos, sales charts)
Holborn 6500 (a flexible reaction to the IBM PC)
Established in 1979, with previous experience at Holland Signal, who used Motorola microprocessors, they chose the Z80 to avoid conflict. They got a design house to come up with the beehive shape for the 9120 terminal units - the 9100 computer was cabinet-sized. The 7100 was cost-reduced but expandable to meet 9100 capability. Software was in ROM, user data on 8" floppy.
The 9100 and 7100 computers ran all programs and the operating system HOS (Holborn Operating System) from ROM. The data could be stored on 8" diskettes. The machines were then made customer-specific. There are various brochures for jewelers, opticians, small businesses, etc. (see downloads)
However, due to the software in ROM, the machine was not very flexible. CP/M was on the rise and it was time to start serving this market as well. Moreover, there appeared to be a demand for even smaller and personal computers without a system idea, which was paid dearly. In order to ultimately be able to participate in the CP/M world, Holborn has developed a 6100 system. This is also in the Technical Museum.
There is still uncertainty about which machines can now run certain software. According to the brochures, a 9100 can also run CP/M and a 6100 would also support HOS. According to several former employees, this was not the case. Not all options mentioned in the brochures were actually possible. But there are also people who report that the 6100 could indeed run HOS and the 9100 CP/M. However, no hard evidence has been found so far. There is no known 9100 system running CP/M and no 6100 running HOS.