BBC Acorn - test-drb@ccmp.vtda.org

12 Dec 2002

On Dec 11, 23:50, Tony Duell wrote:
...
  On Dec 11, 15:36, Joe wrote:

 >    Today I went and picked up another part of my lot of computers that
 > I bought last week. One of the things that I brought home today was a
 > BBC Acorn computer. I'd heard of these but never seen one before. I was
 > pleasantly surprised to find that this one was apparently built for use
 > in the US and that it operates from 110 VAC 50 or 60 Hz and has a US
 > style power plug.  Does anyone know how many of these were imported into
...
  > the US?  I'm assuming that since it's set
up for US power system that it
...
  > will also operate on standard US TV and monitor
frequencies. Does anyone
...

 THere is a US version of the BBC Micro. The differnces are the MOS ROM
 (MOS = Machine Operating System, nothing to do with the technology of the
 chip), which programs the 6845 for US frequencies and the colour encoder,
 which generates NTSC rather than PAL video. Oh, the master Xtal must
 change too, I guess... 
The crystal for the colour circuit does, but not the main crystal.

...
   know for sure.
 BTW the model number on this one is UNB 09. All the
 Acorn websites that I've found only list models A, B and B+ so I'm not
 sure what this is equivelent to. 
 The A and the B are really the same machine. It's just that the A has
 many chips missing (half the RAM, the ROM select register, the user VIA,
 the RS423 buffers, etc). There are also spaces on the PCB for options
 that are not standard in either the A or the B -- the disk controller,
 Econet interface, Speech system, etc.

 The B+ is different. It has many more custom ULAs in it, and 64K RAM.

 From the model number on your machine, I would
assume it's a B, but I am 
 not sure. 
I don't need to add much to what Tony has said, except to confirm that what
you have is indeed (from the model number) a USA Model B.  Other (minor)
differences are things like it accepts American spellings for BASIC
keywords ("color" vs "colour"), and IIRC some of the screen modes
have
different numbers of lines.  I guess I should go and look up the technical
notes for you...

-- 
Pete						Peter Turnbull
						Network Manager
						University of York