30 Jan
2011
30 Jan
'11
10:06 a.m.
Tony Duell wrote:
Actually yes, that would likely make sense, if the video's all running via the
connector on the CPU board - the system bus therefore wouldn't be hooked to
anything and so might not need termination.
Indeed.. I have an idea you can make a cassette-based system that way.
Interesting - presumably the colour PAL board also does the bus termination
(my bus terminator card's also labelled as being for black and white video,
although components for that aspect aren't fitted - presumably it was used on
40x25 systems without the hi-res option)
I am a little puzzled. AFAIK you can make a minimal system with no bus
cable or termiantor atall -- just the CPU board linked ot the 40 column
VDU. Video output comes from the VDU card. Do you have any idea waht sort of components
could be fitted on the
terminator bord? Are there spaces for (DIL) ICs, or jsut discretes?
For the video portion: modulator, "video in" and "video out" sockets
(two
ground pins on each and one for signal), and then a handful of discretes.
For the termination portion: 4 capacitors, 1 resistor, 3 diodes, a 16-pin IC
that's likely a resistor network, and two 18-pin ICs that have had their
markings ground off (bastards!).
It actually says "Black and white modulator / bus terminator board" and then
"BWM 1/1" on the PCB which for RML is unusual - I don't think any of their
other boards list their purpose like that. Copyright date is 1981, so it's not
like it's a very early board or anything. (the PCB itself is a pale green and
quite transparent - in my photo I can see PCB traces for the reverse side -
which is different to all the other RML boards that I've seen, too)
Maybe third-party?
I wonder if it hints at there being another variant of the 40x25 video board
around which doesn't have the modulator on-board? Or maybe the terminator
Not that I know of. The 80 column one doenst' ahve a modulator AFAIK, but
then 80 column text ona TV is likely to be unreadable anyway. My guess is
that it's for the hi-res output.
Yes, that was my assumption, that Adrian just
doesn't have the RGB board. I
thought that all machines with hi-res had that output board too, but that's
No. We had 380Z when I was at school, and they all had hi-res, mono
monitors (litlte 9" Hitachi ones) and no RGB boards. I remeber in my
final year at school converting the school's Barco monitor to have RGB
inputs and fitting the RGB output board in one of the 380Zs.
The 380Z I picked up at a radio rally had the RGB board in it.
There are at
least 2 versions ofthe 5.25" machine. One has a pair
offull-heigfht drives fitted horizotnally, the otehr has a pair of 2/3
height (!) drives mounted vertically. The latter seems more common.
That's interesting. Mine has the horizontal drives, and I always thought of
those as being the most common :-) I think I did a detailed inventory of the systems at Bletchley and emailed it to someone many
moons ago - I'll have to
see if I can dig that out. Of the five or six systems they had, I don't think
any two were quite alike.
That sounds like RML :-)
-tony