ProDigit wrote: ↑
Mon Jul 29, 2019 7:22 am
As far as I understand, Vector displays, crt or LCD shouldn't matter.
Except that nobody makes a vector LCD display.
If a 4Mhz CPU can display 5 moving vectors on a 320x240 (0.75Mpix) screen at 24Hz, in theory a 1,6 Ghz CPU being over 400.000x faster, should …
No, you misunderstand: vector displays don't have pixels. Raster computer displays no longer have an electron beam scanning inside a CRT. Every pixel of the display is refreshed at a fixed frequency, even if it's not illuminated.
On a vector display, though, the beam doesn't even touch the parts of the display if they're not lit. In its simplest form, a vector display uses three analogue signals — X, Y and brightness — to draw the screen. Once it's drawn all the items in the display list, it goes back and refreshes them, possibly in their new position if they've moved. If you magnify a line on a vector display, there are no pixels or steps: only glowing phosphor. Vector displays do filled areas very badly, where it's no extra effort on a raster display.
The Atari vector machines might've had 320 x 240 addressable points, but that only means they had a minimum DAC width of 9 bits horizontally and 8 bits vertically. We can simulate them today with very fine dot-pitch LCDs, but we're pumping millions of times more information to the screen to do so. It's a hardware problem: vector-scan LCDs are not manufactured.
The wikipedia Vectrex
article has a good description of how a simple vector display worked. The old Tek displays produced useful output at 1024 by 780 addressable points when fed at 2400 baud; by contrast, the most you could do with a raster display at that speed is 10 × 10 pixels at 24 Hz, monochrome — a measly 0.0001 Mpix!
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