Newbie questions

[+bent_pin]

I recently acquired 2 working TI99/4As and I purchased 2 finalGROMs, so I have one for each. I downloaded a bunch of programs from ftp.whtech.com. Looking forward to seeing the capabilities of the system. I got these to dig into TMS9900 assembly programming with stock hardware.

 

Is it possible to store data to the cartridge being emulated by the finalGROM? If so, is it the same speed as storing data in a file on a floppy disk?

 

What is the cheapest way to emulate a floppy drive? I have piles of various microcontrollers so if there's a guide to making one, that would be helpful.

 

How many floppy drives can the system support?

 

I see that editor/assembler requires a memory expansion. I'd prefer to avoid too much more investment. Is there a cross-compiler that will let me write GROMs without it? 

 

Can new OS GROMs be created and used on finalGROM?

 

It looks like there are internal GROMs and that many external GROMs can be loaded at the same time too. Is the code available for the internal GROMs? What do I read to better understand this?

 

From the schematic, it looks like someone tripped and dumped a bunch of 16-bit processors into 8-bit backplanes? What happened there?

 

The internal GROMs and the scratchpad RAM are 16-bit, but the 16K of RAM on the video card and all the external busses are 8-bit? All memory expansions are also 8-bit? Anyone every explore a 16-bit memory expansion that saddles the CPU? 

[Reciprocating Bill]

1 hour ago, bent_pin said:

I got these to dig into TMS9900 assembly programming with stock hardware.

The only practical way to do this is using the MiniMemory cartridge - which the FinalGrom can emulate - along with the very basic Line by Line Assembler (also available on the FinalGROM). This enables assembly programming with a pair of tweezers. You'd have approximately 4k of CPU RAM to work with and save and restore to cassette. The Mini Memory can also store files created by TI-BASIC, but (IIRC) it can't be configured simultaneously for file storage and assembly programming. Further, the file storage feature is only useful with the actual physical Mini Memory cartridge, which has a built in battery and can retain its contents when removed from the console. 

 

Fully equipped, the system supports three floppy drives. The TIPI provides (by far) the best drive emulation (and much more). Writing and reading to it seems to be about 3x faster than to/from floppy. Storage with the TIPI is almost unlimited, for all practical purposes (small TI files, gigabytes of SSD storage via raspberry PI).

 

Groms are serial devices running on their own very slow clock and executing programs running on what amounts to a virtual machine (the GPL interpreter). 

 

The 16-bit thing is an historical shit-show all its own. RAM expansion is on the 8-bit bus with wait states for multiplexing. But there indeed are modifications that piggy back 32k of of 16-bit RAM onto the ROM chips, putting the expansion on the 16-bit bus, no wait states, and providing up to a 50% performance kick. Alternatively, there are cards (the SAMS being the most prominent) that provide paged RAM WAY beyond 32K. Can't have both, though.

 

 

Edited August 4, 2023 by Reciprocating Bill

[+arcadeshopper]

FAQ has a lot of these answers

 

- floppy drive needs a disk controller.. or a TIPI 

- finalGrom99 can't be storage but it can be a minimemory cart (4k!) which is limited but how a lot of people learned assembly

 

ultimate set up is the console, a fg99, SAMS1mb sidecar and TIPI sidecar board stack.. and a rasp pi for storage/network connection via TIPI 

I stock these at arcadeshopper.com

 

- Can new OS GROMs be created and used on finalGROM?  -  created yes, used no.. FG only does cart roms.. it doesn't have the circuitry to override the console GROMS, there were products to do this, the GramKracker for one..but its limited to 80k of RAM/GRAM vs uber is 1mb there's a grom replacement project here: 

Lots of good info here on the console and groms;

https://www.unige.ch/medecine/nouspikel/ti99/titechpages.htm

https://archive.org/details/tibook_ti994a-intern

https://archive.org/details/tibook_the-orphan-chronicles

[Stuart]

9 hours ago, bent_pin said:

From the schematic, it looks like someone tripped and dumped a bunch of 16-bit processors into 8-bit backplanes? What happened there?

The TI-99 was originally designed to use the 8-bit TMS9985, but that had problems and never made it into production, so TI stuck in the 16-bit TMS9900 and the 8<>16 bit multiplexer.

[+mizapf]

To be precise, as far as I know, the TMS9985 was also designed as a 16-bit processor, but with 8 data bus lines (like the TMS9995 in the Geneve). The bit count should only be used for the architectural width, not for the data bus width.