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:

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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

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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.


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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.

~David

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