TI-99/8 Games?

[Retrospect]

Obviously it never made it to market but we've got it emulated now in a fashion.

 

Has any games ever been made for the 99/8 ?  Also , it states it has 62 K of free memory available , does anyone know if all 62 K can be saved to cassette?  

I'm toying with the idea of making something for it once I get back into programming.  Dunno when that'll be.  

[jrhodes]

Makes me wonder why they didn't try for 64k instead of a odd sounding 62k.

Looking forward to what you can cook up 🙂

[Retrospect]

I'm tinkering now just for something to do, easy come easy go.  I'm not gonna do an 8-hour session though because that's part of what wore me down beforehand but it's nice to have a play.

 

Graphics are drawn in magellan and it's actually quite fun to type them straight out to the 99/8 by hand. It'll be a cassette game just to be novel.  A simple enough premise for now.  

 

 

[Retrospect]

  Do NOT play this sound file whilst wearing headphones. (Right click, Save Audio As ...... )
 

 

Video and WAV file of game so far.  There's no text file because I'm typing it straight into the 99/8 emulator.  Doing it old school!  

 

 

 

 

 

[Retrospect]

prototype.zip < Wav cassette file

 

This is all I'm doing for today.  My eyes are going funny again.  lol.  There's a spider in the woods now.  It will move at random speeds, and then suddenly stop dead, just to be an arsehole.  

On my next update I'm going to make the spider do only two things ... either move, or stop dead.  No random speeds, as this is slowing the player movement down a little.

 

 

 

[Retrospect]

3 hours ago, jrhodes said:

Makes me wonder why they didn't try for 64k instead of a odd sounding 62k.

It's a straight 64K machine but I guess BASIC needs some space reserving for system stuff.  I dunno.  It's not actually that bad when we compare to what we got with the C64 and Atari 8 bit's.  38.9K and 37K respectively remaining out of 64K.  

 

I'm just hoping the 99/8 has the ability to record more than 13K to a tape otherwise it's gonna be a bit shitty.  

[jrhodes]

39 minutes ago, Retrospect said:

 

(Right click, Save Audio As ...... ) 👈 VERY IMPORTANT!

😳 🎧 Headphone warning! Do not play this while wearing headphones! (Like i stupidly did. Missed the note in parenthesis)

I think my ears are bleeding lol.

@Retrospect How about calling it "Eric in 99/8 Land"?

[Retrospect]

Just now, jrhodes said:

Do not play this while wearing headphones!

😅 i had mine on when i loaded it back in 

 

Hey that's not a bad title really.  

[+OLD CS1]

5 hours ago, jrhodes said:

Makes me wonder why they didn't try for 64k instead of a odd sounding 62k.

My guess is memory-mapped I/O or ROM.  As an example, the Commodore 64 has a full contiguous 64k of RAM, but only about 38k of that is available to BASIC as the RAM is "under" (shares address space with) 16k of ROM, 8k of I/O space, and color RAM.  Now, on the C64 it is possible to turn off ROMs or I/O space, provided nothing needs to use them (no or re-mapped IRQ, NMI, BRK, &c.)   With some clever interrupt management, it is possible to give more RAM to BASIC and change its pointers to use it.

 

Anyway, in terms of the 99/8, I suspect the memory mapping is similar but not swappable, so 4k had to be lost to something: DSR ROMs, I/O, whatever.

[+FarmerPotato]

I'm not certain but I recall the 99/8 has 2K of RAM at 8000. The memory maps appear there. You can set any  24-bit base address  for each 4K bank (with I think 16 byte alignment?) That's all done in an ASIC chip. 

The extra 2K RAM concept began with the 4B spec of Dec 1981, immediately after the 4A shipped. It stuck around through the 99/8. 
 

The idea was to have just enough CPU RAM in the low-cost machine to support fast execution of code downloaded from cartridge  GROMs. The high-end 99/8 or whatever could load many more banks at once into RAM. But the same cart could still run on a 4B with 2K.

 

Low-cost 99/4B died, as the 4A absorbed all the cost improvements but none of the new features. 
 

 That spec changed more times than (colorful metaphor)    A later 4B developed a 19-bit extended physical address (512K) by adding an 8-bit base , shifted left 11 bits. Then any 2K-aligned memory could appear in each of 16x4K banks. 

 

 

The address arithmetic was done outside the CPU, with TTL full-adders, at the start of every memory cycle. 

 

And that leads into the 99/8, having a full 24 bits of base address to add for any 4K logical block. 

This against the backdrop of a 990, which could partition the 64K logical space into 3 ranges, each one a window into 2MiB at any 32-byte alignment. (LMF instruction.) Those bases were stored in TTL registers!

 

Anyhow, TLDR the 99/8 had 2K for scratchpad at 8000-87FE. 

 

(Note from Ron Wilcox to Mike Bunyard says: "nope we can't move SOUND away from 8400" and so there was a PAL to make that a 2 byte hole At 8400.)

 

 

 

(I could be off by powers of 2 anywhere.)

 

[+mizapf]

Everything that I gathered from documents in order to implement the emulation of the TI-99/8 (in particular the memory maps) can be found in the comments of the file

 

https://github.com/mamedev/mame/blob/master/src/devices/bus/ti99/internal/998board.cpp

 

(beginning and lines 1077ff., 1570ff., and more)

[kl99-interims]

On 4/8/2023 at 4:37 PM, jrhodes said:

Makes me wonder why they didn't try for 64k instead of a odd sounding 62k.

Looking forward to what you can cook up 🙂

the whole 99/8 project had to work under the limitation to keep 99/4a compatibility.

the 99/2 project didn't had that limitation.

i guess this might be the origin for the 99/8 limits.