c164-1bj@cordelia.berkeley.edu (Jonathan Dubman) (11/07/87)
On the subject of using the interleave trick to double scan rate or increase screen depth or resolution or whatever: (context determines meaning) In article <605@rover.UUCP>, mph@rover.UUCP (Mark Huth) writes: >I think that's where the interleave comes in. Instead of fetching >sequential samples from the same ram chip, you fetch sequential samples >from different banks of ram. Maybe I have four ram banks... >...With sequential addressing like you have in video display applications >the interleave technique works real well. Just use some of the low order >address bits to generate the chip select signals. You forgot that the Amiga's whole graphics architecture is built around graphics structures that do not live at fixed memory locations. I had this idea when a friend of mine was working on a 768x512 graphics board a few years ago, and it's very tempting: for 8 bit planes, just have 8 rows of chips, pull out a bit from each, look up the corresponding 12 or 18 or 24-bit color register - pipeline the thing so you fetch ram data and look up the next color register at the same time - fancy D/A - and presto! Instant mind-blowing graphics with no 30ns expensive static RAM, no muss, no fuss. Change 8 to 24 bit planes - basically no increase in fuss, save for the large motherboard space and one HELL of a color register table - heck - scrap the color register table - that's just a temporary solution to the inequality 2^bitplanes << palette size (Ok - there are other advantages - the color indirection is very handy...) Anyway, such a gimmick is not likely to work in the [current!] design of the Amiga, because the screens can reside anywhere - the Amiga uses yet another level of indirection. That plus the programmable copper gives us the scrolling screens that are a human interface work of art (separate environments for separate programs - much less confusing) In short, the interleave gimmick makes it hard to do zippy multiple-screen scrolling dual-playfield type graphics - unless I'm wrong and the design is not that limiting. *&Jonathan "\0" Dubman I finished the semantic analyzer!!! Now I can read the 435 messages. P.S. (TM, Adobe systems) I seem to have the habit of talking about ten things at once. Multitasking is affecting my brain. NEW YEAR'S RESOLUTION: 1024x800