26 Jan
1998
26 Jan
'98
6:44 a.m.
I'm not that impressed with the 3270pc. I bought
it because I wanted
stuff out of it, but it was all pretty much proprietary (and covered
in dust and old) lots of wire wrapping and jumpers, so I just left it
alone. Now I use it to test Linux-16.
The REAL question is, if IBM used these as terminals which could run
software, what did they have in them allowing them to use the network
ports? I mean that was 1984, DOS might have had some hooks, but they
would have sold it.
Were these running XENIX/86, CPM86, or what? Anyone know? Anyone have
the software...
Um. As I recall, when you booted a 3270PC, it booted MS-DOS from the
hard disk as usual. Early on in the boot procedure, it loaded some sort
of 3270-terminal-operating-system which grabbed some memory somewhere,
locked DOS out of it somehow and REBOOTED. DOS then loaded normally
UNDERNEATH the terminal program.
The 3270 PC had some extra keys on the keyboard - the function keys (24
of them) were where they are on a modern PC keyboard, but there was a
block of keys where they were on the original PC keyboard. These keys
did things like switch between your terminal session and your PC
session. The keyboard plugged into the terminal card as well as the
keyboard port, BTW - I think the terminal card filtered out stuff that
wasn't meant for the DOS session. The point was, DOS never knew about
the terminal unless you specifically piped data through the terminal
program.
IBM sold an API (Application Program Interface) which was a piece of
software allowing programs running on the PC to type on the terminal,
look at the terminal screen memory, etc. Very crude. File transfer
software - not very good - was available too.
The reason they were rare was that the IBM 3270 terminal protocol (SNA,
Systems Network Architecture) was only used on IBM mainframes - not even
on the System/3X minis. I don't know how it worked but it was EBCDIC
for a start...
Returning to the 5155, when I was working at IBM this was the cheapest
complete system in the IBM range - it was much the same price as an XT
(if not less) and it had a monitor built in. Many IBM employees bought
them as an entry level system (IBM required us to sign a contract saying
we wouldn't develop software for other than IBM machines - I don't know
whether this would have survived a court case!) But there must be some
around if only for that reason.
Hope this helps!
Philip.
PS *** Off Topic ***
Will Sam and Anthony please go and have their argument somewhere else?
The first couple of posts about Anthony's personal testimony were
interesting and related to computers. The subsequent argument about
drugs and off-topic posts, not to mention mature adults of 17 and silly
kids of 30 (I'm one of the latter FWIW) was not.
Sam, you say Anthony has problems - but so do you. Will you stop
jumping down everybody's throat as soon as the topic starts to drift,
please?
Finally, alcohol. Interesting points about Prohibition (which we didn't
have over here). Thank you whoever posted them (even though off topic).
Denatured alcohol here is still "Methylated Spirit" - i.e. it has had
methanol added. It has also had pyridine (I think) added to make it
look purple and taste foul, and it is therefore even more poisonous, but
it doesn't leave a residue.
On the subject of home-made booze, if you use the wrong sort of yeast,
you may well get methanol in the ferment. During prohibition I'd guess
that proper brewer's yeast was not easily available! Apparently
potatoes are particularly susceptible, and this has given the
traditional Irish spirit made therefrom, Poteen, a bad name for making
you literally "blind drunk."
Since I am a non-drinker I'd better say no more on that subject...
Philip.