Another UK101 user
Posted: Sat Jan 11, 2020 10:15 pm
I got my UK101 as a kit back in 1980 while I was still at school and used it for a couple of years before moving on to a BBC Micro in 1982.
Like others here, I made many mods to it and built several add-ons during that time and even came up with a mod myself that got published in the UK's PC world magazine.
Fortunately I kept it and it still works today, but only just, as the board often needs flexing or the chips need reseating to get it to boot after it's been left for a while. I think it needs a complete overhaul!
The mod that was published in PC world eliminated the noise during screen access by synchronising the video circuitry to the CPU's phi1 clock so that there was never any conflict and thus no noise when the screen memory was written to and it didn't affect the speed of screen updates.
The same technique was used by other 6502 based systems like the Apple II and BBC micro and I'm surprised it wasn't designed like that to begin with as it didn't require any extra circuitry, just a slight re-arrangement of the signals although it may have made the timings on the screen memory a bit marginal.
I suppose a similar mod could be made to the Superboard.
Other mods I can remember were:
switchable 16 and 32 line display (Which also switched to 16 and 32 line versions of the 2K monitor ROM)
switchable WEMON monitor ROM
switchable BASIC ROMs
EXMON in EPROM
6821 PIA board (veroboard on the right) which I used to control a home made EPROM programmer and it also controlled a "VOXBOX" speech synthesizer
Creed 7B teleprinter interface (vertical veroboard on the left) with built in EPROM based driver so I could print listings
Unfortunately the teleprinter went to the scrapyard a long time ago
Like others here, I made many mods to it and built several add-ons during that time and even came up with a mod myself that got published in the UK's PC world magazine.
Fortunately I kept it and it still works today, but only just, as the board often needs flexing or the chips need reseating to get it to boot after it's been left for a while. I think it needs a complete overhaul!
The mod that was published in PC world eliminated the noise during screen access by synchronising the video circuitry to the CPU's phi1 clock so that there was never any conflict and thus no noise when the screen memory was written to and it didn't affect the speed of screen updates.
The same technique was used by other 6502 based systems like the Apple II and BBC micro and I'm surprised it wasn't designed like that to begin with as it didn't require any extra circuitry, just a slight re-arrangement of the signals although it may have made the timings on the screen memory a bit marginal.
I suppose a similar mod could be made to the Superboard.
Other mods I can remember were:
switchable 16 and 32 line display (Which also switched to 16 and 32 line versions of the 2K monitor ROM)
switchable WEMON monitor ROM
switchable BASIC ROMs
EXMON in EPROM
6821 PIA board (veroboard on the right) which I used to control a home made EPROM programmer and it also controlled a "VOXBOX" speech synthesizer
Creed 7B teleprinter interface (vertical veroboard on the left) with built in EPROM based driver so I could print listings
Unfortunately the teleprinter went to the scrapyard a long time ago