Path: utzoo!utgpu!water!watmath!clyde!att!ucbvax!ucsfcgl!cca.ucsf.edu!root From: root@cca.ucsf.edu (Computer Center) Newsgroups: comp.arch Subject: Re: Sw vs. Hw BitBlit. Summary: For the "dominant" uses one should not be blitting at all any more Keywords: BitBlit. Message-ID: <1315@ucsfcca.ucsf.edu> Date: 28 Jul 88 22:52:20 GMT References: <399@ma.diab.se> <1313@ucsfcca.ucsf.edu> <61783@sun.uucp> Organization: Computer Center, UCSF Lines: 43 In article <61783@sun.uucp>, guy@gorodish.Sun.COM (Guy Harris) writes: (In an attempt to refute my point about substituting word-blitting for bit-blitting without admitting it being a debater's trick). > > For applications in terminals, there are three cases of "bitblt" that > dominate: drawing characters, scrolling windows and window-window > operations such as exchanging off-screen data with the display. These > cases also cover the most common graphics operations on personal > computers. > ... > > from "Hardware/Software Trade-offs for Bitmap Graphics on the Blit", Rob Pike, > Bart Locanthi, and John Reiser, Software-Practice and Experience, Vol. 15(2), > 131-151 (February 1985). > Another debater's trick: this one is called Appeal to Authority. Never mind, I suppose, that this is 3 1/2 years after publication of the above and who knows how long before that it was written. A few things have happened in this business since then. But the real point is that these are exactly the applications that should not be blitted at all; the video mapping controller should be handling all of that. For example, at last month's Usenix meeting Bell Technologies was showing their Intel 82786 (I hope I got the number right) video controller running smoothly scrolled text over 2/3 of a high-res screen while occupying the remainder with instant opening and closing overlapped windows. No jerks, no glitches, no skew were to be seen. It sure made the skew distorted scrolling of the corner cutting move-screen-bits-with-the-cpu systems look awful. Thos Sumner (thos@cca.ucsf.edu) BITNET: thos@ucsfcca (The I.G.) (...ucbvax!ucsfcgl!cca.ucsf!thos) OS|2 -- an Operating System for puppets. #include