David Boyes wrote:
There's only one manufacturer, and only for ESCON, not FICON.
Channel
adapters are about US $6000, by the time you get drivers, etc for
them.
_I_ don't know whether Fortune 500 finds that expensive. When we
bought
out 168s, we might not have (back then the $US was only worth about
70c).
The problem is less the expense than that IBM is pushing very hard to
get people to FICON (with good reason). Most big shops have done the
forklift upgrade to FICON and don't HAVE any ESCON left (or are trying
to get rid of it ASAP). The smaller shops would find that fairly pricy.
There have in the past been
cards one could install in a PC to give it the ability to emulate a
local 3270-style console. One of those, with new programming, might
do
the job.
Via coax, yes. You still needed a 3x74, which puts us back in the
host-doesn't-see-the-keystroke model.
Is that a controller device? I'm suggesting the PC connect as a
controller. Unfortunately, we're on my wrong reply:-(
I wasn't aware there were controller devices that would connect to a PC
other than a 7171. In that case, wouldn't you need both channel and coax
adapter? Or were you thinking of something like MS SNA Server that just
front-ended a single DFT connection?
I was wondering whether there is/suggesting there ought to be something
that attaches a PC directly to a channel.
The pc would function as a channel, and it's devices _could_ be ssh
sessions.
I don't recall the controller model numbers, and I think the relevant
books are in the garden shed, but when the 3270 family was first
released we had 3277 displays that plugged into a 3271 or a 3272
controller: the first was local (channel attached), the other remote.
The 3275 was a 3277 with a built-in remote controller.
The 3272 was the local controller, and connected to a channel (I suspect
a block multiplexor channel would have bene first choice, but maybe
selector if there wre no tapes around).
Then one plugged the 3277s into the 3271 or 3272 control units using
coax cables.
A PC would, of course, handle just the kind of communication that Linux
requires. What is needed is the physical attachment to it can be
connected to a channel, and VM support for it, and VM emulation of it.
VM's role would be about that of a channel.
There would be no channel program running against the PC until it
generates an interrupt, just as the 3271 does when a user presses an
attention key. Then, something creates a channel program to read
whatever the PC wants to send. While the overhead for reading individual
bytes might be high, you wouldn't ordinarily be running more than 15 per
second per virtual device attached to the pc, depending on how fast you
can type.
If this were done, then anything that could be connected to a PC could
be connected to the mainframe, through the PC, it's only more software
in the PC and another driver in the host. This might increase the data
rate, but with burst-mode transfers I don't think it should be
excessivly expensive.
--
Cheers
John
-- spambait
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