donn@utah-cs.UUCP (11/23/86)
In all this folderol about the Teletype DMD 5620, I noticed one interesting point fly by and disappear. Guido Bertocci (twitch!guido) mentions that the 5620 can run at 19.2 Kbaud. In my experience this is misleading -- flow control and protocol overhead limit the throughput to ~300 cps in layers. My beat-up old Ann Arbor Ambassador gets 1900+ cps at 19.2 Kbaud. This is one reason why I have a triple-A in my office instead of a 5620. Another problem with the 5620 has been lack of software. Rob Pike demonstrated features of the Blit software at the Santa Monica Usenix back in 1982 which I still haven't seen on a 5620. (I understand through the grapevine that the situation has improved recently, although (of course?) we haven't encountered anyone who is actually running the new stuff.) The expense of the 5620, the limitations of the software and the slow speed have combined to kill off any interest our user community might have developed. The only way someone here might conceivably buy another 5620 would be if (a) the speed improved to handle 19.2 Kbaud without flow control, (b) the price dropped to the same as an Ann Arbor terminal, and (c) someone put X windows up on it (:-). I wouldn't mind hearing that (a) and (c) are in a $10 upgrade kit, Donn Seeley University of Utah CS Dept donn@utah-cs.arpa 40 46' 6"N 111 50' 34"W (801) 581-5668 decvax!utah-cs!donn
gwyn@brl-smoke.ARPA (Doug Gwyn ) (11/25/86)
In article <4037@utah-cs.UUCP> donn@utah-cs.UUCP (Donn Seeley) writes: >... flow control and protocol overhead limit the throughput >to ~300 cps in layers. The protocol is multiplexed, full-duplex, error-correcting packets with relatively little overhead for large data transfers. However, if you transfer a single byte per packet, the overhead is naturally substantial. (The original "jerqio library" implementation suffered from this.) Rob Pike reported over 16,000 user bits per second on a 19,200 baud line, on 8th Edition UNIX. (He also reports no more than 6,000 baud effective rate on other implementations.) If you're using a user-mode multiplexer based on ptys on a 4BSD kernel, then the context switching alone will eat you alive. Doug Kingston published a kernel-mode 4BSD multiplexer modeled after AT&T's "xt" pseudo-device driver that runs much faster. >Another problem with the 5620 has been lack of software. Rob Pike >demonstrated features of the Blit software at the Santa Monica Usenix >back in 1982 which I still haven't seen on a 5620. Dave Prosser's "myx" package (available rather inexpensively through the AT&T UNIX System Toolchest) has most of those features. One point that people who are not heavy DMD users keep missing is that the DMD is designed to be used for more sophisticated user interaction interfaces than simple windows. A typical DMD layer is a downloaded program that has a fairly capable 32-bit processor available to drive the user interaction when it needs it. I have seen some amazing user interfaces, and I'm expecting to develop yet another in a few weeks. People who use the default terminal emulator in a DMD layer to run something like EMACS on the host computer are not exploiting the DMD's capabilities very well.
shap@sfsup.UUCP (J.S.Shapiro) (11/25/86)
> 5620 throughput <> 19.2K
Don,it seems to me that you are confusing things. Your Ann Arbor does not
let you have 6 virtual terminals at a slot, each operating independently.
Ever wish you could *use* that time during a make?
Also, comparing the flow control under layers to the Ann Arbor running raw
is hardly fair. The DMD running raw is just as nice (nay nicer, because
even in raw mode I can download whatever emulator I want) as the Ann Arbor.
Nicer, really, because it doesn't tend to have quite as bad focus problems.
As to 19.2, Frankly I think its uninteresting. Most serial ports on the
computer end can't handle that.
All I can tell you is I use one daily with all of the software I want.
Jon Shapirojrg@hpirs.HP (Jeff Glasson) (11/26/86)
Don't forget the original Heathkit H9.... It was 12X80, uppercase
only (mapped lowercase incorrectly), no remote cursor control (there
were cursor keys, but they didn't generate any ESC sequence),...
This was truly a glass TTY.
Jeff Glasson
Hewlett-Packard
{ubcvax,hplabs}!hpda!jrghurf@batcomputer.tn.cornell.edu (Hurf Sheldon) (12/02/86)
In article <5404@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes: ... >>Another problem with the 5620 has been lack of software. Rob Pike >>demonstrated features of the Blit software at the Santa Monica Usenix >>back in 1982 which I still haven't seen on a 5620. ... or information about what's available > >Dave Prosser's "myx" package (available rather inexpensively through >the AT&T UNIX System Toolchest) has most of those features. ... is there more? >... the user interaction when it needs it. I have seen some amazing user >interfaces, and I'm expecting to develop yet another in a few weeks. ... will you share it? >People who use the default terminal emulator in a DMD layer to run >something like EMACS on the host computer are not exploiting the DMD's >capabilities very well. ... maybe so but it does work nicely - can it run emacs locally? Say - do you know how to get a larger font in the tek4010 window? We have several 3b2/dmd systems - We are ignorant of the possibilities & would much appreciate any helpful suggestions & software. I was excited when I realized we had the real magilla blit that A.K. Dewdney wrote of but where is a standard reference on what it can do & how to do it? Hurf Sheldon Arpa.css: hurf@ionvax.tn.cornell.edu Lab of Plasma Studies 369 Upson Hall phone: 607 255 7267 Cornell University Ithaca, N.Y. 14853
gwyn@brl-smoke.ARPA (Doug Gwyn ) (12/04/86)
In article <1617@batcomputer.tn.cornell.edu> hurf@batcomputer.UUCP (Hurf Sheldon) writes: > will you share it? [referring to a DMD user interface I'll be developing] Sure, when it's ready I'll announce it somewhere. Is this the right newsgroup? I'm one of the old-timers who would rather give away useful software than sell it; I think there's only a few of us left.. > do you know how to get a larger font in the tek4010 window? The font menu uses two character sizes with 4 inter-character spacings. (One can lock the font in so that set-font codes from the host have no effect.) Since the "tek4014" program attempts to emulate a scaled Tektronix 4014, no larger fonts are available. By the way, "myx" (although not a Tektronix emulator) supports other fonts besides the default. > We have several 3b2/dmd systems - We are ignorant of the possibilities & would >much appreciate any helpful suggestions & software. I was excited when I >realized we had the real magilla blit that A.K. Dewdney wrote of but where >is a standard reference on what it can do & how to do it? References: ACM Transactions of Graphics, Vol 2 No 2 (Apr 1983) pp 135-160: Rob Pike, "Graphics in Overlapping Bitmap Layers" describes the fundamental algorithms underlying layers (not really necessary for DMD programmers, since this code is mostly hidden within the system and libraries) AT&T Bell Laboratories Technical Journal, Vol 63 No 8 Part 2 (Oct 1984) pp 1607-1631: R. Pike, "The Blit: A Multiplexed Graphics Terminal" overview, design philosophy, implementation, etc. pp 1633-1647: T. A. Cargill, "Debugging C Programs With The Blit" describes what is essentially the same as "dmdebug" AT&T documentation available from their Customer Information Service: select code 306-140: 5620 Dot-Mapped Display User Guide how to use the basic utilities (tek4014, jim, dmdp, etc.) select code 306-141: 5620 Dot-Mapped Display Administrator Guide how to install DMD software, etc. select code 306-142: 5620 Dot-Mapped Display Application Development Guide DMD programmer's reference manual and instructions for "icon" select code 306-143: 5620 Dot-Mapped Display Text/Graphics Guide how to use cip & proof select code 306-144: 5620 Dot-Mapped Display Reference Manual "UNIX manual" pages; essential for programming DMD applications The AT&T UNIX System ToolChest offers some DMD programs; descriptions can be had by dialup modem access ((201)522-6900, login "guest"). Last time I dialed up, some months ago, I found the following: $price $transmission name description 60 ? centipede Insect Shooting Game 125 69.50 dmd-pgmg Collection of Teletype 5620 DMD Prog's (includes "myx") 95 ? dmdps Bitmap Printer Interface 75 ? gebaca Corporate Logo Shooting Game 1200 ? paw Graphic Model Builder and Simulator I mail out my own implementations of "dmdp" and "crabs" upon request (Gwyn@BRL.MIL). Doug Kingston (DPK@BRL.MIL) has posted some useful software to the INFO-BLIT mailing list, which seems dormant at present. To join the mailing list, send a note to INFO-BLIT-REQUEST@BRL.MIL. I took an excellent 5-day DMD programming course at AT&T's Lisle, IL corporate education center, but I haven't seen that course offered recently. My suggestion is to get the two AT&T manuals flagged above as useful for programming, obtain the AT&T DMD core and text+graphics source packages (you also need the application development binaries) and some programs such as "myx", and use the existing source code and reference manuals as a guide for what to do. Start with some of the simpler "demo" program sources and modify them experimentally..