4 ms·

The lack of machine language programming out of the box was deliberate and similar to Apple's App Store business model. If you wanted to be a serious developer

The lack of machine language programming out of the box was deliberate and similar to Apple's App Store business model. If you wanted to be a serious developer for the platform you had to buy an expensive 32K upgrade and floppy drive. Then you could use the assembler and other languages. The RAM thing was an architectural choice - you weren't really meant to use the 256 bytes of SRAM for your programs, you were meant to share 16K of RAM with the video processor and make all read and write requests via the video chip. (You could access the 32K expansion directly)

PaulHoule 4y ago
I'd say the 99/4A was unique among the 8-bit computers. All the rest had basically the same architecture, but the TI had that strange system where most of the RAM had to be accessed through in's and out's.
- abecedarius 4y ago
  A 16-bit machine slower than most 8-bitters. I did find the instruction set to be nice to code for once I'd upgraded enough to get access to assembly.
- lproven 4y ago
  > All the rest had basically the same architecture Z80 (Tandy, Sinclair, Amstrad, Elan, Memotech, etc.) 6502 (Acorn, Commodore, Atari, Oric, etc.) 6809 (Tandy, Dragon, etc.) Some with a "GPU" that generated screen output, some without. Some with sound generators, some without. Some with disk interfaces as standard, some without. Some with standard ports (Centronics parallel, RS-232 serial, IEEE, etc.) some without. The same architecture?!
  - TMWNN 4y ago
    >The same architecture?! Yes, the same architecture. You know what PaulHoule meant, and if you didn't you should have. It's a fact that * It is relatively easy to port between computers with the same 8-bit CPU * It is harder, but still quite possible, to port between the Z80 and 6502 * Very, very little software was ported to the 99/4A, and until the end the lack of software was a major issue for a computer that sold almost 3 million units The 99/4 architecture by and large baffled developers. Partly because of the unique CPU, but also because of fundamental design differences. I know of no Z80 or 6502-based computer which abstracts things the way 99/4 does. There is no TI equivalent (I'm talking about deviations from the prescribed norm, not the functionality per se) to the Atari 8-bit and TRS-80's multitude of DOSs, the C64's fast loaders, the Atari 8-bit's Happy Drive, Star Raiders and Eastern Front on Atari, Pinball Construction Set and Prince of Persia on Apple II, GEOS on C64. Since you're British, I'll add 3D Monster Maze on ZX81, Elite on BBC Micro, The Lords of Midnight and Knight Lore on Spectrum. Even the Color Computer, benighted by the 6809 CPU almost as unfamiliar to Z80 and 6502 developers as TMS9900, birthed Dungeons of Daggorath.
    - lproven 4y ago
      Hmmmm. OK. I guess. This is not any standard definition of "architecture" that I recognise, but I think I see what you are getting at.
KerrAvon 4y ago
The App Store model only works if developers want to build apps for your system. In the microcomputer market, even IBM couldn't afford to make that assumption. Every successful vendor had to evangelize and grease the skids for developers as much as possible.
sidewndr46 4y ago
So the video chip functioned as a sort of memory controller? I've heard of people using modern GPUs to store arbitrary data. But that was just because it's there, it's fast and it is not in use most of the time. But this is different.
- II2II 4y ago
  It probably isn't as crazy as it sounds. Graphics consumed a considerable amount of the memory on early personal computers. It looks like one of those video modes could consume about 75% of the 16 kB. Of course, that is cherry picking the most memory hungry mode. Other modes would use less memory, leaving unused memory for programs to use. If anything, it looks like the TI-99/4A is different since it appears to be designed for programs to use video memory because it's there and offers very little dedicated memory for the CPU.
- nsxwolf 4y ago
  Yes, that chip was the TMS9918A and it was also used in systems like the MSX computers and the Colecovision game console. The Colecovision was similar in that it offered 1KB of "scratchpad" RAM the CPU could directly address, and 16K of video RAM shared with the VDP. The chip used auto-incrementing address registers that would allow a CPU to read from and write to VRAM.

PaulHoule 4y ago

I'd say the 99/4A was unique among the 8-bit computers. All the rest had basically the same architecture, but the TI had that strange system where most of the RAM had to be accessed through in's and out's.

abecedarius 4y ago
A 16-bit machine slower than most 8-bitters. I did find the instruction set to be nice to code for once I'd upgraded enough to get access to assembly.
lproven 4y ago
> All the rest had basically the same architecture Z80 (Tandy, Sinclair, Amstrad, Elan, Memotech, etc.) 6502 (Acorn, Commodore, Atari, Oric, etc.) 6809 (Tandy, Dragon, etc.) Some with a "GPU" that generated screen output, some without. Some with sound generators, some without. Some with disk interfaces as standard, some without. Some with standard ports (Centronics parallel, RS-232 serial, IEEE, etc.) some without. The same architecture?!
- TMWNN 4y ago
  >The same architecture?! Yes, the same architecture. You know what PaulHoule meant, and if you didn't you should have. It's a fact that * It is relatively easy to port between computers with the same 8-bit CPU * It is harder, but still quite possible, to port between the Z80 and 6502 * Very, very little software was ported to the 99/4A, and until the end the lack of software was a major issue for a computer that sold almost 3 million units The 99/4 architecture by and large baffled developers. Partly because of the unique CPU, but also because of fundamental design differences. I know of no Z80 or 6502-based computer which abstracts things the way 99/4 does. There is no TI equivalent (I'm talking about deviations from the prescribed norm, not the functionality per se) to the Atari 8-bit and TRS-80's multitude of DOSs, the C64's fast loaders, the Atari 8-bit's Happy Drive, Star Raiders and Eastern Front on Atari, Pinball Construction Set and Prince of Persia on Apple II, GEOS on C64. Since you're British, I'll add 3D Monster Maze on ZX81, Elite on BBC Micro, The Lords of Midnight and Knight Lore on Spectrum. Even the Color Computer, benighted by the 6809 CPU almost as unfamiliar to Z80 and 6502 developers as TMS9900, birthed Dungeons of Daggorath.
  - lproven 4y ago
    Hmmmm. OK. I guess. This is not any standard definition of "architecture" that I recognise, but I think I see what you are getting at.

KerrAvon 4y ago

The App Store model only works if developers want to build apps for your system. In the microcomputer market, even IBM couldn't afford to make that assumption. Every successful vendor had to evangelize and grease the skids for developers as much as possible.

sidewndr46 4y ago

So the video chip functioned as a sort of memory controller? I've heard of people using modern GPUs to store arbitrary data. But that was just because it's there, it's fast and it is not in use most of the time. But this is different.

II2II 4y ago
It probably isn't as crazy as it sounds. Graphics consumed a considerable amount of the memory on early personal computers. It looks like one of those video modes could consume about 75% of the 16 kB. Of course, that is cherry picking the most memory hungry mode. Other modes would use less memory, leaving unused memory for programs to use. If anything, it looks like the TI-99/4A is different since it appears to be designed for programs to use video memory because it's there and offers very little dedicated memory for the CPU.
nsxwolf 4y ago
Yes, that chip was the TMS9918A and it was also used in systems like the MSX computers and the Colecovision game console. The Colecovision was similar in that it offered 1KB of "scratchpad" RAM the CPU could directly address, and 16K of video RAM shared with the VDP. The chip used auto-incrementing address registers that would allow a CPU to read from and write to VRAM.