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Don't Mess with Texas – TI-99/4A Megademo [video]

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Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#41

Post by joakleaf »

Olivier26 wrote: post #36
nsxwolf wrote: post #26

Earlier quoted context omitted.

I don't have any problem believing this can run on real hardware. One of the programmers, Tursi, has done some amazing things that do indeed run on the real thing. I'm not sure what you're counting as "vanilla", but a TI with the Speech Synthesizer and the 32K RAM expansion is vanilla to me. Those are utterly ubiquitous and period-correct OEM upgrades. If it required the F18A, which is an FPGA implementation of the T…

> TI with the Speech Synthesizer and the 32K RAM expansion is vanilla to me Agree > graphics chip with some significant new features on it, I'd agree that wouldn't count. Agree too. If the graphics chip was so powerful, it's hard to understand why it was so underused, and not integrated in other microcomputers of this time. The video memory of the TI was 16KB, I had several computers with this size, and you couldn't…

From Wikipedia: --- • Multicolor mode: 64×48 pixels (each pixel may be any color, all 32 sprites are available)

• Bitmap mode: 256×192 pixels (no more than two colors in an eight pixel row, full 15 color palette + transparent, all 32 sprites available)

• Graphics mode: 32×24 characters (256 8×8 user-definable characters, full 15 color palette + transparent and 32 sprites. ---

The last was the mode accessible from Basic and Extended Basic. I remember longing for the bitmap and multicolor mode.

For the 256x182 mode, the pixel bitmap is 5824 bytes bitmap, plus 1 byte for color info of each 8-pixel (4-bit foreground/4-bit background) which is also 5824 bytes. Total 11648 bytes. Just 2 bits per pixel BTW.

The TI994a had 32 sprites (all single colored 8x8 pixels). You could also magnify them.

Also from Wikipedia: --- The TMS9918 was the basis for the VDP chips in the Sega Master System, Game Gear and Mega Drive. They used additional display modes and registers, and added hardware scrolling capabilities and other advanced features. (Note that the Mega Drive VDP cannot access any of the TMS9918 display modes discussed below.) ---

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#42

Post by nsxwolf »

Olivier26 wrote: post #36
nsxwolf wrote: post #26

Earlier quoted context omitted.

I don't have any problem believing this can run on real hardware. One of the programmers, Tursi, has done some amazing things that do indeed run on the real thing. I'm not sure what you're counting as "vanilla", but a TI with the Speech Synthesizer and the 32K RAM expansion is vanilla to me. Those are utterly ubiquitous and period-correct OEM upgrades. If it required the F18A, which is an FPGA implementation of the T…

> TI with the Speech Synthesizer and the 32K RAM expansion is vanilla to me Agree > graphics chip with some significant new features on it, I'd agree that wouldn't count. Agree too. If the graphics chip was so powerful, it's hard to understand why it was so underused, and not integrated in other microcomputers of this time. The video memory of the TI was 16KB, I had several computers with this size, and you couldn't…

Actually the TMS9918 is used in a lot of places - in addition to the MSX (which I see you noted below) it was also used in the Colecovision game console and Sega's SG-1000 among others.

The sprite support was great, especially for the late 1970s. Though, I continue to be impressed with what an unencumbered architectire like the Apple II can do with sprites purely in software.

Sega actually kept going with the architecture - the Sega Master System used an upgraded 9918 based chip, and the Genesis/Mega Drive built further on top of that.

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#43

Post by Olivier26 »

joakleaf wrote: post #38
Olivier26 wrote: post #31

Earlier quoted context omitted.

Well, Parsec is very far from this demo, if the window is small it's for speed. The demo is full screen, which is impressive. And Parsec is coherent with what the hardware had to offer for the 3D those years, like Elite.

Parsec was 2D horizontal smooth scrolling. It wasn't full screen, but the scrolling screens in this demo generally contains repetitive graphics, which would allow them to use a number of possible tricks. I actually downloaded and tried the demo on the Classic99 emulator, and it works exactly as advertised. Would love to see actual hardware demo though.

Same here, it works even with the F18A option disabled. So I apologize to these talented developers!

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#44

Post by boomlinde »

pm215 wrote: post #16
joakleaf wrote: post #7

I grew up and learned basic on a TI-99/4a. It was a wonderful and simple time... but TI Basic was so incredibly slow. At least Extended Basic allowed you to use sprites and overall felt a bit faster. In TI Basic, you accessed the more interesting parts of the machine "Call" functions (e.g. "Call Color", "Call Char", "Call hchar", etc.), and I always found Commodores peek/poke mess very primitive and a bit more inacce…

The slow BASIC was due to the completely insane doubly-interpreted implementation. The BASIC interpreter was written in GPL (Graphics Programming Language; https://en.wikipedia.org/wiki/Texas_Instruments_TI-99/4A#VDP... ), which was itself interpreted at runtime.

If I understand that correctly, the BASIC programs were stored in VDP RAM. If that's anything like the MSX (most of which also used this video chip), that means that BASIC tokens are read from a slow 8-bit bus by writing addresses byte by byte to a port and reading the content from another.

There's functionality to automatically increment the VDP address, but any non-contiguous read will have to write the VDP address to the port.

I really like this layered design despite its performance impact. It meant that they could fully utilize the VDP RAM where the CPU local RAM was lacking.

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#45

Post by YZF »

arundelo wrote: post #27
Narishma wrote: post #20

Earlier quoted context omitted.

The contemporary of the Apple II and TRS-80 was the Commodore PET. The C64 came much later.

I'm talking about 8-bit microcomputers in general, from the late seventies to the mid-to-late eighties: https://en.wikipedia.org/wiki/Home_computer#Notable_home_com... EDIT: I owned a Commodore 64 and a TRS-80 in the eighties, and used an Apple IIe at school. These were all programmable in Basic, and although the C64 was clearly the most powerful, they were all similar in power compared to, say, an Amiga.

The Amiga used the 68K so it was more powerful than the previous microcomputers that were mostly 6502 (some Z80).

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#46

Post by pm215 »

boomlinde wrote: post #44
pm215 wrote: post #16

Earlier quoted context omitted.

The slow BASIC was due to the completely insane doubly-interpreted implementation. The BASIC interpreter was written in GPL (Graphics Programming Language; https://en.wikipedia.org/wiki/Texas_Instruments_TI-99/4A#VDP... ), which was itself interpreted at runtime.

If I understand that correctly, the BASIC programs were stored in VDP RAM. If that's anything like the MSX (most of which also used this video chip), that means that BASIC tokens are read from a slow 8-bit bus by writing addresses byte by byte to a port and reading the content from another. There's functionality to automatically increment the VDP address, but any non-contiguous read will have to write the VDP address…

Not only the BASIC programs you wrote (which do indeed live in VDP RAM). The BASIC interpreter itself was stored in GROM, which was read-only but had a similar slow 8-bit interface with an address port and a data port on it, and written in GPL bytecode which was then interpreted by a GPL interpreter which lived in real ROM.

If they'd written the BASIC interpreter in actual machine code and put it in ROM then your BASIC programs (and the interpreter's own volatile data) could still have lived in VDP RAM, but everything would have been rather faster...

http://www.unige.ch/medecine/nouspikel/ti99/gpl.htm is a detailed description of what GPL looks like.

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#48

Post by 13of40 »

ddrager wrote: post #40

Oh wow, the TI-99/4A, I learned BASIC on this computer! If you didn't have the tape storage unit, which could save data onto an audio cassette, you had to re-type your program into the computer if the power went out or unit was reset. It also had an external voice processor as an addon which was really creepy https://www.youtube.com/watch?v=kUPkCNcT1Yw

It was my family's first computer and the one I wrote my first programs on. Three things that stuck in my craw about it were:

1. BASIC supported PEEK but there was no POKE.

2. You could save files to a disk but you had to remember the file names because there was no way to list them.

3. Lower case letters were just small versions of uppercase.

For the last one, a year or so ago I actually found a dump of the Apple IIe font and hacked an emulated TI-99 to use it, and it worked and looked great, so I have no idea what they were thinking.

Anyway, it's awesome to see them be able to squeeze so much out of it in this demo.

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#49

Post by nsxwolf »

joakleaf wrote: post #38
Olivier26 wrote: post #31

Earlier quoted context omitted.

Well, Parsec is very far from this demo, if the window is small it's for speed. The demo is full screen, which is impressive. And Parsec is coherent with what the hardware had to offer for the 3D those years, like Elite.

Parsec was 2D horizontal smooth scrolling. It wasn't full screen, but the scrolling screens in this demo generally contains repetitive graphics, which would allow them to use a number of possible tricks. I actually downloaded and tried the demo on the Classic99 emulator, and it works exactly as advertised. Would love to see actual hardware demo though.

I have the real hardware ready to go, but I don't currently have an easy option for getting software from the internet onto it. I see they made a ROM cartridge version of it; if they ever make a run of those for sale I'll definitely grab one.

Re: Don't Mess with Texas – TI-99/4A Megademo [video]

#50

Post by pjmlp »

apo wrote: post #33

Good times. I owned one of these. The TI-99/4A was never very popular, but there was one store called "The Bach Company" on San Antonio Road in Palo Alto that specialized in selling hardware and software for it. It's easy to forget just how hard it was to get software for a home computer in the early 1980s. If you had a modem, then you could use bulletin boards, but the first 300 baud models (plus required RS-232 int…

On my home town in Portugal the only BBS available could only take about 5 simultaneous connections, nevermind the outrageous prices for connecting outside the city center.
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