Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!gatech!akgua!usl!elg From: elg@usl.UUCP (Eric Lee Green) Newsgroups: net.periphs,net.micro,net.wanted Subject: Re: update on **real** 19200 CRT Message-ID: <855@usl.UUCP> Date: Mon, 4-Aug-86 01:17:30 EDT Article-I.D.: usl.855 Posted: Mon Aug 4 01:17:30 1986 Date-Received: Tue, 5-Aug-86 05:47:33 EDT References: <671@mordred.purdue.UUCP> <71@winfree.UUCP> <2349@cbosgd.UUCP> <604@ulowell.UUCP> <15071@ucbvax.BERKELEY.EDU> Reply-To: elg@usl.UUCP (Eric Lee Green) Organization: USL, Lafayette, LA Lines: 64 Keywords: Amiga,Macintosh, calculator gymnastics, scrolling speed Xref: mnetor net.periphs:493 net.micro:5757 net.wanted:3599 In article <15071@ucbvax.BERKELEY.EDU> mazlack@ernie.Berkeley.EDU.UUCP (Lawrence J. Mazlack) writes: >In article <604@ulowell.UUCP> page@ulowell.UUCP (Bob Page) writes: >>Since you're thinking about going micro-based, check out the Amiga. >>text/background, and it works great at 19200! Of course, you can >>still multitask all you want (recalculate your spreadsheet while you >>download a file, etc). Nice to have a window-based system. >>..Bob >>UUCP: wanginst!ulowell!page Bob Page, U of Lowell CS Dept > >Could you send me an exact list of hardware/software that I would need to >do this. I could then explore doing it with my purchasing people. (My >micro choice is a Mac - hardly a cost effective way of achieving a 19200 >baud terminal.) A Macintosh won't run at 19200 baud. To scroll the screen, it needs to move 32K of RAM. I would estimate it takes at least 20 clock cycles per word to move it, which would be roughly 320,000 clock cycles for the whole thing. That's only 25 newlines per second that would be allowed before the terminal started falling behind... lines would need to average over 77 characters to not lose text at 19200 baud. Obviously, a Macintosh would simply not work as a 19200 baud terminal... simply too slow due to insufficient hardware support for high-speed bit moves. Hmm, the Amiga blitter would take 32,000 cycles, which is 250 newlines per second that would be allowed... adequate, perhaps, you would still fall behind on lots of under-8-character lines. An Amiga with educational discounts sells for about $1600 full-blown, still too expensive, but it's kinda like a SUN for poor people... The 8Mhz. PC-clone would take about about the same amount of time to scroll 2000 bytes, using the CPU to do the data movement. As someone pointed out, if your CRT controller supports scrolling, a scroll is only about 200 cycles of tightly hewn assembly code (clear the new bottom line, move the pointers, presto)... but PC-Kermit would almost certainly use the BIOS routines, which probably don't take advantage of any such features. A PC-drone with Hercules card and monitor would probably cost around $1200... inexpensive, but cheap. By the way, method of calculation: newlines_per_second = 8,000,000/newline_cycles (8Mhz = clock cycles per second) minimum_line_length = 1920/newlines_per_second minimum_line_length is minimum average line length necessary to not fall behind due to newline scrolling speed. 1920 is of course characters per second. None of the mentioned computers should have too much problem with just placing characters upon the screen matrix -- it'd take pretty much to eat up 4166 clock cycles unless the terminal program was written in interpretive BASIC :-). This inner loop would probably need to be in machine language. Most PC "C" compilers I have seen are memory hogs that produce awful code. Terminal commands, however, would definitely be a speed problem... some fairly heavy padding may be needed for deleting and inserting lines, which on the average require moving half the screen. Geez, one sure can get carried away with a calculator! -- If I am elected no one will ever have to do their laundry again! (YOW!) -- -- Computing from the Bayous, -- Eric Green {akgua,ut-sally}!usl!elg (Snail Mail P.O. Box 92191, Lafayette, LA 70509)