Meet the Holborns ...
I contacted user Roland Huisman on the VCFED forum if he was willing to share ROMs and disk images for this fabulous looking machine, and he kindly sent me his complete archive - thanks Roland!
I'll get that up to the FTP later ... it would be great if the machine could be added to MAME. The disk images seem to contain some personal information, so we'll have to see what can be shared.
There was actually a whole range of machines from Holborn before they succumbed to bankruptcy in the early 80s. Following is my summary of the models combined with Roland's corrections and additions: 6100 series:
6110: CPU (Z80, serial port to connect to the terminal board, SASI interface board if you have a harddisk), monitor and keyboard in a desktop case (the terminal board is the same as the one in the later model 9120 terminals, see note there)
6140: two 8" floppy drives or one 8" floppy drive and one 12MB hard disk drive in an external disk unit. Floppy A: and B: are DSDD. If you want to read SSDD or SSSD disks then you have to go to the C: for the A: drive and to the D: for the B: drive. That makes E: the first letter for the first hard disk partition and F: for the second.
There were several hard disks sold. The first ones were 5MB Rodime disks. Holborns are not capable of booting from a hard disk. All the HD settings are on the floppy! So when you have such a machine without a floppy, then you have a hard time to get to the original data on the disk.6500 series
One site mentions only one prototype was made, but there are two known in existence, one in Roland's hands. They were never actually sold, but one of the original employees said he remembered that there were some 6100 machines in the field which were upgraded to 6500 specs.
6510: Pictures show a 6110 style case (but smaller in depth) with two 5.25" disk drives "popping up" on top and a seperate model 6530 keyboard.
One other picture has a "Holborn 6500" terminal that's missing the disk drives - you could use a secondary terminal on the serial port when you run MP/M.
I have done that and it works on the Holborns! Multi user os! 😊
The system boards are interchangeable between the 6110 and the 6510, they are identical with the 6110 and already have the 34 pin floppy header for 5.25" drives.
The 5.25" disks are 77 tracks, just like the 8 inch disks. You can write the 8" disk images onto the 5.25" disks and vice versa.9100 series:
9110: CPU and four 8" floppy disk drives in a floor rack, up to three or four terminals, configured to customer's specs - max four 8" drives.
And I thought max 4 terminals... But I have to check that if you want to know more about it.
9120: Terminal with a lightpen. There are two versions of the 9120 terminal. The old ones have a Beehive terminal inside. You can recognise these 9120 terminals on the long row of black keys on the top of the keyboard. The later 9120 terminals had Holborns own terminal board inside. The same as in the 6100!
Very often you see the 9120 terminal on top of a 9100, but that was not how they were used. The 9100 has a paper tray inside that can feed a printer on top of the cabinet through a door on the back of the machine.
7100 series: same hardware and software as the 9100 series, but limited to two terminals. The 7100 could be field upgraded to 9100 if a customer wanted that. There are just a few empty sockets to fill...
Roland's archive contains ROM and disk dumps for the 6100 and 6500 series, but he mentioned he could get hold of the 9100 series ROM dumps as well.