dale@amiga.UUCP (Dale Luck) (07/15/87)
For you guys that need 120 hz refresh but can get by with half the number of lines are your display, you could try this. I haven't tried this out , but it shoudl work. Write the beam counter in the middle of the display to bump it down to the end. I don't remember if the copper can write the beam counter, the chip designers might have gone crazy again with their arbitrary limitations. But anyway, write it so it is about 255 or so, it will then continue counting up to 262 or so and trigger vblank and the display will start again. Most monitors should not have any trouble with this. Well, I'm no hardware guy so that is just a guess to. This response prompted by some guy in toronto wanting to quad lace the display. I remember the tektronics stereo displays were running at twice refresh rate so this idea just popped up. Meaning they were interlacing at 120 instead of 60hz per field. Oh well, happy hacking Dale
stever@videovax.Tek.COM (Steven E. Rice, P.E.) (07/15/87)
In article <1699@amiga.amiga.UUCP>, Dale Luck (dale@amiga.UUCP) writes: > For you guys that need 120 hz refresh but can get by with half the number > of lines are your display, you could try this. > I haven't tried this out , but it shoudl work. > Write the beam counter in the middle of the display to bump it down > to the end. I don't remember if the copper can write the beam counter, > the chip designers might have gone crazy again with their arbitrary > limitations. But anyway, write it so it is about 255 or so, it will then > continue counting up to 262 or so and trigger vblank and the display > will start again. Most monitors should not have any trouble with this. > Well, I'm no hardware guy so that is just a guess to. No luck, Dale! Most monitors will ignore a vertical interval in the middle of the active picture area. Those that don't will have a fit trying to synchronize to something that is twice normal rate. (The deflection magnetics are usually resonated at the scan rate to reduce drive power requirements.) > This response prompted by some guy in toronto wanting to quad lace > the display. I remember the tektronics stereo displays were running at ^^^^^^^^^^ Aaaaaarrrrggggggghhhhhh!!!!! That's TEKTRONIX!!! No "c"s. No "s"s. > twice refresh rate so this idea just popped up. Meaning they were > interlacing at 120 instead of 60hz per field. Special monitors. Big bucks. Not interlaced -- progressive scan (how progressive!). Since the liquid crystal light valve can switch polarization between frames, every other frame is a "left eye" frame. Steve Rice ----------------------------------------------------------------------------- new: stever@videovax.tv.Tek.com old: {decvax | hplabs | ihnp4 | uw-beaver | cae780}!tektronix!videovax!stever