B3_B3_B3 wrote:I always wondered about the bbc B's excessive amount of built-in ports (and thus unnecessary added cost for unused circuitry) e.g. many were unused on mine (disc and printer were eventually used):
Most of the extra interfaces you say are typically unused are not present on the Model A, though this is only by omitting the components from the PCB - the space to fit them is still there.
If you wanted a machine with 32Kb of RAM without the extra I/O you could fit the extra RAM chips. Looking in the service manual dealers had instructions on how to create an A+ (my term) which had the extra RAM and the user VIA but none of the other options.
B3_B3_B3 wrote:Also, I thought Centronics printers of the time were viewed as less hassle to setup than serial....
For a personal printer, they were. I still remember going to a computer centre where we setting up equipment to capture screen dumps from a terminal - we attached a computer to the printer port and wasted much time because the technical guy at the centre concerned was adamant about the baud rate, strt & stop bits etc. Only when I fetched the protocol analyser and discovered what settings where really in use did we make any progress. You don't get that hassle with a centronics I/F. On the other hand the centronics I/F has limited cable length - you can't so easily sent to a printer in another room or even at the end of a modem.
B3_B3_B3 wrote:An agreed(officially suggested) way of wiring Atari joysticks to user port pins could have allowed MOS/BASIC Joystick support.....
I think this another question in the category of "Why was the BBC not better optimised for playing games" to which the answer is "that was not the focus of its design". For the TV series one would be much more likely to demonstrate controlling robotics via the joystick, hence the choice of an analogue one, capable of proportional control rather than Atari-style. It was nevertheless common practice to connect game-playing hoysticks to the analogue port and once you did that the OS support for a joystick would work fine.
B3_B3_B3 wrote:Also, without RS423 port perhaps serial UART IC could have been dropped from main board* and the cassette bit-banged like on Electron (but I suppose they were probably in a hurry_). *but moved to optional Econet daughterboard/section.
It may be a co-incidence but at the time I remember the BBC micro having much more reliable tape loading than some of the other machines of the time and it occurs to me this might be specifically because it uses a proper UART for the tape interface.
B3_B3_B3 wrote:Would an extra internal '1Mhz' style Bus interface and IDC header for the Disc Interface have avoided needing disc interface specific ICs on main board, saving purchasing cost / giving smaller main board/ allowing design to be deferred/changed to 1770 later? Similarly for the econet section of board.
Also, it could be easier to attach a daughterboard to an IDC header than solder new chips to the motherboard.
I think there is a clear design philosophy with the BBC micro to keep things neat by having things inside the single case and to me this is very much preferable to the mess of interconnected boxes that might otherwise have been. On the other hand, given that there was no room inside the case of 5 1/4" disc drives and therefore an external enclosure was needed, and given the later trend for having a power supply inside the case with the disk drives, it would have been a neater design to mount the floppy disc controller hardware on a PCB inside the enclosure with the drives and have that box then connect back to the BBC 1Mhz bus. It would also have been good to define an OSWORD interface for reading/writing raw sectors from the disk and formatting discs that wasn't tied to a specific FDC and didn't extend to doing trickery with the hardware, so that the choice of FDC would be up to whoever was supplying the DFS ROM to go with the disks. But hindsight is wonderful thing.
I am not sure the same would apply to econet - it's a simple cable connection so having the optional hardware fitted internally as required is preferable to external. On whether to put it on a daughter board I suspect the relative cost of PCB space vs. the semiconductors to go there was rather different than it is today.