General Category > LisaList2
Adding a parallel DAC Sound device to the Lisa (was Insane Questions)
stepleton:
I'm all for this project :)
The Lisa parallel port is very different to the PC parallel port --- the fact that bits come in a row is where most of the things in common begin and end, I think. I guess they're both 5V, there's that too. Still, you ought to be able to get a Speech Thing to work. I like the idea of whacking together some sound hardware from stuff lying around in drawers. Plus, got a 2-port parallel card? You've got stereo!
Sometimes though I have to admit to wondering what you could do with just the built-in hardware. An IBM PC with a 4.77MHz 8088 can play a MOD file on the speaker if you happen to be a demo wizard, with cycles left over to print the end credits.
I don't know much about this stuff, but the demo I linked seems to take advantage of the fact that the PC has a programmable square wave generator (i.e. a particular way of setting up the 8253 timer). In the Lisa, the speaker is hooked up to a pin on one of the 6522s (CB2) that acts as a shift register, and furthermore it seems like you can get a 6522 to generate somewhat arbitrary square waves too if you want by shifting out the same byte over and over --- the last page of this PDF has the details. Whether this facility has a comparable frequency range to what you can do with an 8253 is beyond me. But, it may be possible --- and, with the Lisa, you have volume control, so you can do dynamics. My bet is that you can play samples on a stock Lisa with no peripherals.
I'd love to try it but I have a hard drive emulator hardware bug to fix :)
blusnowkitty:
I only bring up the 6504 because I know the Lisa is a very slow system as it is, and I'm kinda throwing ideas at the wall to see what sticks as far as, what does a stock Lisa have that could possibly give me every extra clock I can get hardware-wise?. I guess I had the Sega Mega Drive in mind, which is also a 68000-based system that uses a secondary CPU for sound (in this case, a Z80). But if the Lisa's 6504 has no ability to access anything other than its own disk drives, that kinda renders that point moot, doesn't it? :D Plus the Mega Drive is a games console, with an 8MHz 68000, 8KB of RAM on the sound CPU, dedicated graphics processors... all of which the Lisa doesn't have... Still, there's gotta be something you can use the 6504 for. This needs further experimentation.
Hey Tom, what tool were you using to copy your floppy bootloader .bin to track 0?
rayarachelian:
--- Quote from: blusnowkitty on January 26, 2021, 09:56:05 am ---I guess I had the Sega Mega Drive in mind, which is also a 68000-based system that uses a secondary CPU for sound (in this case, a Z80).
--- End quote ---
Yeah, I'm familiar with the Sega Genesis/Mega Drive, as the CPU core in LisaEm is from http://www.squish.net/generator/ - but yeah. You could make it work with the 6504, but it won't be easy. Plus there's no Yamaha synth chip in there either.
stepleton:
--- Quote from: blusnowkitty on January 26, 2021, 09:56:05 am ---Hey Tom, what tool were you using to copy your floppy bootloader .bin to track 0?
--- End quote ---
I'm using a homemade all-in-one python program. Just give it a program with the ORG set to $800 for the bootloader to load, and it gives you a bootable floppy image.
Navigation
[0] Message Index
[*] Previous page
Go to full version