Bryan

I've been looking over the topic and I have a quick question. I discovered a while back that you could get a triangle by letting 2 square waves beat out of phase. Basically, the output would shift between 2 voltages: While in phase, and for sufficiently high oscillator frequencies, you would get the true average of (max+min)/2. While out of phase, you would get the electrical average based on the resistor output network in Pokey, resulting a slightly different value. This makes the output shift back and forth creating a triangle, but a very quiet one. To make matters worse, I don't think it produced the same output level in every Pokey. I experimented with different volume levels and adding extra channels to it, but haven't looked at it in some time. Has another method to generate triangles been discovered yet?

I just realized I'm limited to 32 characters that will repeat cleanly (I was thinking it was the other 96), so this really isn't useful for much. I'm better off managing a full-screen bitmap.

Actually, one more question: if the last line of a VSCROL area has a value set higher than 7, would it just keep looping without intervention? Edit: Actually, I'm guessing the normal character height is ignored and it just counts until it matches.

Awesome, thanks.

I haven't done any Atari programming lately, but I had an idea that requires me to get around the 100% bus usage of the first line of IR2 in a few spots. Now, I could make that region IR15, but that would add a lot of overhead. Is there a way using an out of range VSCROL value (like, maybe 8?) that will read the character names once, then show all 8 character lines twice? That way, I could simply swap character sets for the 2nd 8 lines and get different data while being able to do mid-line writes everywhere except the first line. So... I want one badline to get the character names on line 0, then lines 1,2,3,4,5,6,7,0,1,2,3,4,5,6,7, totaling 16 lines, 2 character rows of the same thing. - I know entering a VSCROL region starts on the line you specify, but will the character end when line 15 wraps to 0, or only when line 7 wraps to 0? - I know exiting a VSCROL region starts on 0 and exits on the line you specify. Does selecting something higher than 7 keep repeating the character? - I'm aware that lines 8&9 would have limitations due to IR3 always being active in there somewhere. I think I can just rearrange the character set. - If this method won't work, is there another way to fake Antic out? I guess in my mind, Atari programming isn't fun unless you're hammering the hardware in some way to make the impossible happen. Normally, I'd whip something up but I'm rusty enough to ask before I try to get set up to code again (any good thread on the best way to code alongside Altirra these days?) Thanks, Bry

The whine generally comes from old diskettes where the oxide coating isn't as slippery as it originally was causing oscillation against the felt pad. There's not much you can do but transfer to disks in better condition. Some brands held up a lot better than others.

I didn't see it mentioned in the thread (pardon me if it was) but I remember a story from Atari engineers that Texas Instruments was a big driving force behind the new FCC rules. They were trying to get the TI99 to market and representatives from Texas were pushing to relax the rules to help them pass testing.

Just thinking here... There may be a way to get some crude alignment on 2 voices with AUDCTL, especially if you can base some pitches off the 15KHz clock. Load the intended pitch, but flip to the 1.8MHz clock until you want the wave to start. You'll get ultrasonic (silent) waves until you flip back and then the slow wave starts. EDIT: I guess that's no better than cramming a divisor of 0, though except that it would affect 2 voices at once. Although flipping to the fast clock would run out the timer on the current pitch quickly since you can't align anything until the counter expires.

Just the datasheets, app notes and emulation info on old voice chips. Looking at the requirements. Well, I believe you can align a voice by: 1. knowing the cycles since Pokey was reset (using WSYNC alignment or maybe triggering an interrupt off a voice?) 2. cramming a short pitch value (perhaps at 0 volume) to delay the next square wave. Cycle counting would be needed, but at least locking to scan lines makes it deterministic. I've also thought about the sounds Alley Cat makes. It's possible there's enough poly sounds already in there that would be suitable for a crude robot voice if you could find them all.

After reading old documentation on speech synthesis, I'm convinced that intelligible speech can be done on Pokey without the overhead of sampled phonemes. You need to identify the main frequency components and type of noise (f, s, t sounds) needed and change them at regular intervals through the phoneme. The poly sounds could be really good for getting basic combinations of frequencies too.

Sometimes the drive spindle or clamping cone bearings have dried out. Note when testing the cone bearing that it won't spin freely unless it is pressed down into the spindle hub (when the door is closed).