Wednesday, September 28, 2016

IRIS with Device 033 and 027, DKP and DZP

This page is a part of the "Understanding IRIS" collection.  Many thanks to David Takle, for figuring this out, and sharing this with us:


On this SimH Migration page, David says 

"Very few drivers existed on IRIS for standard DG controllers using Device 33"

I asked David to expand the thought by stating what Device # most Point 4 IRIS systems had a tendency to use.  was it 027?

I remember wrestling with this issue before I met David

The first I ever heard of it was when Bruce Ray analyzed the first file I ever pulled off of these tapes, which I quote in Minicom Disk To Tape Utility tells a story...

"The utility assumes two devices exist: a tape controller using device code <022> and a disk controller using device code <027>. The tape controller may or may not perform QIC to DG-style file handling emulation since the original tape is not available to me.

The disk controller appears to use the standard DG "Zebra" controller (Model 6060/6061/6067) programming model. However, it assumes a non-standard disk geometry of 16 cylinders, 5 heads, and 32 sectors."

Device 027 wasn't an option in SimH, nor was it in the Bruce Ray's reNOVAte Demo Version 4.0B.06, only in his later, full-function versions, which I never accessed.

By then I was facing the whole DKP vs DZP thing, with device # issues when I was wrestling with Wild Hare's reNOVAte Demo Version 4.0B.06


In answer to the dev. 33 question, it seemed that most IRIS users opted for 3rd party controllers. My guess is that cost was a major factor. Controllers in those days were incredibly expensive, and DG probably charged more than they needed to, which made a market for other engineers to step in and offer their stuff for less.

For whatever reason, they seemed to gravitate more to device 27. So EDS / Point4 either wrote the drivers or got them from the controller manufacturers and distributed them freely in the CONFIG file.


I noticed Bruce Ray mentioned the variety of multiplexors as well.
DG produced a fairly simple one that simply acted like a rack of serial (RS232) devices. When Point4 designed theirs, they went for a high-tech approach with a direct access channel to memory. So it did not have to interrupt the CPU for every character going out or coming in.

I just recently figured out how the SimH supports a multiplexer. I had not given it much thought, because I knew they would only support the DG version and not Point4's DMA version. Turns out that the IRIS backup has a mux driver designed for the DG mux, called $DGMX or just DGMX if it is not enabled. If handled right, it can support a ton of Telnet connections all at once on the Nova.exe. I have already used it several times. It will just take me some time to document the process.

I have also found a couple of great Telnet programs that support really nice terminal emulations as well as transfer protocols like XMODEM. So one of my goals is to write a terminal translation module to support VT320 codes as well as XMODEM transfers, which would make it very easy to transfer files between SimH and Windows --- even binary files.



This page is a part of the "Understanding IRIS" collection.  

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