5 ms·

interesting, I wonder if the common cpu made it easier to port the games for those two systems or possibly a shared compiler? I'm pretty sure the TI994a had so

interesting, I wonder if the common cpu made it easier to port the games for those two systems or possibly a shared compiler? I'm pretty sure the TI994a had somewhat of a video buffer in the form of sprites (I know it was capable of parallax scrolling) and it's own sound chip that was the one used in speak and spells(That may have been a separate module called speech synthesizer). Later models of Atari and Amiga may be the units I am thinking of being very similar.

bluGill 5y ago
The 8 bit Atari design team had a lot to do with the amiga computer. The 16 Atari st series shared a CPU with the amiga, but otherwise was very different.
- timbit42 5y ago
  The Atari ST was largely a 16-bit Commodore 64. The designer was an engineer on the C64 team, Shiraz Shivji.
rbanffy 5y ago
The common CPU helps, but considering how different the machines were, I doubt it’d help that much.
- memsom 5y ago
  That reminded me of this: https://github.com/unbibium/atari64 https://github.com/unbibium/atari64 He ported the C64 KERNAL and BASIC to Atari
  - rbanffy 5y ago
    Must be about twice as fast ;-)
    - timbit42 5y ago
      It is faster but the ANTIC/GTIA steals cycles from the 6502 while the VIC-II cycles are interleaved with the 6502 to greatly reduce cycle stealing: https://www.youtube.com/watch?v=mxi5_VhxkJQ https://www.youtube.com/watch?v=mxi5_VhxkJQ
rbanffy 5y ago
> the TI994a had somewhat of a video buffer The TI 99 had some interesting design choices. The CPU had a very small amount of SRAM, 128 bytes IIRC, because it couldn't easily use DRAMs, which were much cheaper. The BASIC interpreter in ROM would read the program from the VDP's memory (which was DRAM) and interpret it, storing data back into the display controller's memory. It was a really nice 16-bit minicomputer CPU with one of the ugliest hacks around it to make it fit a home computer budget. Legend says IBM almost settled on the TI99's CPU instead of the 8088 for the IBM PC (they also mused about plain acquiring Atari) but didn't go for it because TI would be the single source for the component. The same VDP would be the basis of the MSX, Master System and a couple others.
justinlloyd 5y ago
Outside of the instruction set of the 6502 CPU there was zero overlap between the C64, the Atari 400/800 and the Apple II. There were no common tools to speak of, no common data formats, no compilers (compiler? pshaw! sub-optimal code!), no common memory map, no common audio hardware, and between the Commodore/Apple/Atari of the time, there wasn't any commonality in how the screen memory could be read or written. The BBC Micro (also 6502) and the Apple II did share a common video chip in the form of the MC6845, which was a particularly strange beast to program for, but again, the overlap between those two systems was minimal at best. I wrote code for published games and applications for all of those systems, and more besides like the TI99/4a, including a couple of C compilers.
- rbanffy 5y ago
  The 6845 was only in the Videx cards. Also, on CGA, MDA, and Hercules cards on PCs. The II generated its video using discrete TTL chips.
  - justinlloyd 5y ago
    You know, it is so far in the past now I cannot recall if "The 6845 was only in the Videx cards" is true or not. I suspect you are right and I am confusing Apple's weird video RAM layout with the 6845. Now I need to go check on my old Apple II. Update: You are correct. It appears I have reached "that age."

bluGill 5y ago

The 8 bit Atari design team had a lot to do with the amiga computer. The 16 Atari st series shared a CPU with the amiga, but otherwise was very different.

timbit42 5y ago
The Atari ST was largely a 16-bit Commodore 64. The designer was an engineer on the C64 team, Shiraz Shivji.

rbanffy 5y ago

The common CPU helps, but considering how different the machines were, I doubt it’d help that much.

memsom 5y ago
That reminded me of this: https://github.com/unbibium/atari64 https://github.com/unbibium/atari64 He ported the C64 KERNAL and BASIC to Atari
- rbanffy 5y ago
  Must be about twice as fast ;-)
  - timbit42 5y ago
    It is faster but the ANTIC/GTIA steals cycles from the 6502 while the VIC-II cycles are interleaved with the 6502 to greatly reduce cycle stealing: https://www.youtube.com/watch?v=mxi5_VhxkJQ https://www.youtube.com/watch?v=mxi5_VhxkJQ

rbanffy 5y ago

> the TI994a had somewhat of a video buffer The TI 99 had some interesting design choices. The CPU had a very small amount of SRAM, 128 bytes IIRC, because it couldn't easily use DRAMs, which were much cheaper. The BASIC interpreter in ROM would read the program from the VDP's memory (which was DRAM) and interpret it, storing data back into the display controller's memory. It was a really nice 16-bit minicomputer CPU with one of the ugliest hacks around it to make it fit a home computer budget. Legend says IBM almost settled on the TI99's CPU instead of the 8088 for the IBM PC (they also mused about plain acquiring Atari) but didn't go for it because TI would be the single source for the component. The same VDP would be the basis of the MSX, Master System and a couple others.

justinlloyd 5y ago

Outside of the instruction set of the 6502 CPU there was zero overlap between the C64, the Atari 400/800 and the Apple II. There were no common tools to speak of, no common data formats, no compilers (compiler? pshaw! sub-optimal code!), no common memory map, no common audio hardware, and between the Commodore/Apple/Atari of the time, there wasn't any commonality in how the screen memory could be read or written. The BBC Micro (also 6502) and the Apple II did share a common video chip in the form of the MC6845, which was a particularly strange beast to program for, but again, the overlap between those two systems was minimal at best. I wrote code for published games and applications for all of those systems, and more besides like the TI99/4a, including a couple of C compilers.

rbanffy 5y ago
The 6845 was only in the Videx cards. Also, on CGA, MDA, and Hercules cards on PCs. The II generated its video using discrete TTL chips.
- justinlloyd 5y ago
  You know, it is so far in the past now I cannot recall if "The 6845 was only in the Videx cards" is true or not. I suspect you are right and I am confusing Apple's weird video RAM layout with the 6845. Now I need to go check on my old Apple II. Update: You are correct. It appears I have reached "that age."