Re: PC connection via twinax ?

[Douglas Handy <dhandy1@xxxxxxxxxxxxx>]

Steve,

Can't address the other issues, but

>Back in the day when converting from the s36 to 400, there 
>was an ibm product that allowed data transfer thru the twinax 
>port.  Is it known how to do that?

I believe it was the same way that some early 3x to PC data transfers worked.
Ignore for a minute complications with characters below EBCDIC x'40'.  Create a
display format with a single input field starting at 2,1 and continuing to the
end of the display.  The old DOS based emulators, even IBM very first one,
included a set of APIs to let a PC program examine or change screen contents,
simulate keypresses, etc.

To transfer to the PC, the 3x fills the buffer and display the screen format.
The PC extracts the data out of the emulation buffer and "presses" Enter,
allowing the 3x to fill it with the next screen of data.  

To transfer to the 3x, the reverse is done.  The 3x displays an empty screen.
The PC fills the buffer and "presses" Enter.  The 3x collects the data and
redisplays a blank screen.  The PC "presses" Cmd7 or whatever when done.

Control characters can be handled by a temporary escape to hexadecimal.  Later
the 5250 protocol was enhanced (and documented publicly) to add a "transparency"
subcommand to allow "data" to include characters below x'40' .  Using a 24x80
session you could do up to 1919 characters at a time; using a 27x132 you could
do 3563 and get better performance.

Back on the 36, I used to write programs for specialized bi-directional data
transfers using these techniques.  There were third-party tape drives for the 36
which worked in the same fashion -- they would attach as a 3180 via twinax and
emulate a 27x132 session.

I used one of the boxes you referred to in a 36 to 400 conversion.  It attached
to both WS controllers, and you could have sessions on each and hot key between
them.  For data transfers, it would take as many twinax addresses as you would
allow.  The doc recommended configuring data transfer addresses as 27x132
displays to maximum throughput.  So I'm pretty sure it worked the same way as
the old APIs for the emulator.

No undocumented stuff needed for the transfers.

Doug