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tezza
March 4th, 2014, 03:38 PM
I have a nice TI-99/4a but with few carts or software.
http://www.classic-computers.org.nz/blog/2014-02-22-ti99_4a-reconstituting.htm

Of course there are loads of software images on the net. I was wondering how best to get the software in these into my machine though? Is there a modern solid-state solution? I'm thinking maybe a device which plugs into the cartridge slot but used SD cards or similar to hold floppy images. As far as the computer is concerned it thinks its talking to a disk drive. Such things exist for commodore machines for example.

I'm aware of the HxC Floppy emulator but would like something I don't need to find an extra power source for or mess around with cables. Anything out there?

Tez

OS9dude
March 5th, 2014, 02:13 AM
Been looking for such a solution myself. This is what I found a while back:

http://webpages.charter.net/nanopeb/

Bad news is that it seems to be our of production and the best bet on getting one is Ebay :(


-- RP

gubbish
March 5th, 2014, 10:48 AM
Hi Tez,

I don't know of a simple cartridge-type solution for this, but this is providing inspiration to fire up the soldering iron and try to build one. I think I can reuse the majority of the code for the PETdisk to make a simple TI/99 SD drive on a cartridge board. Looking up the pinouts and specs now.. will try this out over the weekend to see what happens!
- Mike

tezza
March 5th, 2014, 02:42 PM
Hi Tez,

I don't know of a simple cartridge-type solution for this, but this is providing inspiration to fire up the soldering iron and try to build one. I think I can reuse the majority of the code for the PETdisk to make a simple TI/99 SD drive on a cartridge board. Looking up the pinouts and specs now.. will try this out over the weekend to see what happens!
- Mike

Mike!

Great! Go for it!! You'll have the gratitude of many TI-99/4A nostalgerists over the world (and me too)! Unlike a lot of other popular retro-models, a solid-state disk solution for this one seems to be lacking.

Tez

Ksarul
March 5th, 2014, 06:00 PM
The NanoPEB/CF7+ aren't exactly out of production, the guy who builds them is Jaime Malilong (Schmutzig1952 on eBay). He tends to build a batch of them and then sell them on eBay for as long as the pre0built batch lasts. There will be a pause of from one to three months and another batch will show up for sale. They always go really fast. . .

Mike, Tezza is spot-on when he says a lot of TI folks would REALLY like a cartridge slot SD drive. I would definitely be on board for a few (if you were building them) or plans (if you wanted them to go as an individual build thing). Let me know if you need a cartridge board layout to experiment with, as I've done them up in ExpressPCB for other projects--and exported them to Gerber/Excellon format as well.

gubbish
March 5th, 2014, 10:06 PM
Thanks Ksarul, I would definitely be interested in a cartridge board layout to examine, if you have one convenient. I've used ExpressPCB for most of my other projects, so that format would be fine. If you have any pointers to specs and documentation for the TI cartridge interface, I'd be interested in those as well. Planning to design this much like the PETdisk with a micro controller and SD card with FAT32 support in firmware.
Very excited about this project as the TI-99/4A was the first computer we had in our house growing up, and I still have some audio cassettes with my old programs and saved games from Pirate Adventure on them.

barryp
March 5th, 2014, 11:12 PM
Bad news is that it seems to be our of production and the best bet on getting one is Ebay :(

eBay is THE source for them, they rarely will be up for resale, the designer/builder used to auction them one at a time and now typically lists them ten at a time.

Ramdisks would also be popular, I love mine. (25 years old)

jltursan
March 5th, 2014, 11:34 PM
Great to read that gubbish is planning a TI-99/4A "PETdisk" version :D. IIRC I have some loose TI cartidge PCBs that I can scan easily, let me know if they can be of some help.

gubbish
March 6th, 2014, 01:33 PM
Sure, that could definitely be helpful. If you get a chance to scan the PCBs, I'm interested to take a look.
Currently I'm reading through to learn about the TI-99 architecture and how the cartridge port connects to the address and data bus of the computer. If any 99ers out there have any insights into the details about how the system reads from the attached cartridge and the ROM and GROM on the cartridge are structured, I'd be interested in the info. Thanks!
- Mike

Ksarul
March 7th, 2014, 05:48 AM
Here are the files for a cart in ExpressPCB and in Gerber format. I hope they come in useful.

gubbish
March 7th, 2014, 04:59 PM
Thanks! Will take a look at these tonight.
Made a bit of progress on this so far, mainly just reading up on how the TI checks for the presence of a cartridge by reading the cartridge ROM at address >6000, and looking for a certain structure to list the presence of programs on the cartridge and their locations in memory. One of the first steps will be to make a test board which can plug into the cartridge slot and contain the right data to make the cartridge program show up on TI bootup.

Thinking about a couple of use cases for the cartridge SD drive -
One would be as a software multicart which can read ROM images from the card and place them into RAM on the cartridge board so various cartridge images can be selected at bootup.
Another is to load/save cassette-based programs to/from system memory.
And a third is to simulate a true TI floppy drive with support for floppy disk images.

Any ideas on ways you would want to use such a device? Any input is welcomed.. thanks!
- Mike

tezza
March 7th, 2014, 09:59 PM
Thinking about a couple of use cases for the cartridge SD drive -
One would be as a software multicart which can read ROM images from the card and place them into RAM on the cartridge board so various cartridge images can be selected at bootup.
Another is to load/save cassette-based programs to/from system memory.
And a third is to simulate a true TI floppy drive with support for floppy disk images.

Any ideas on ways you would want to use such a device? Any input is welcomed.. thanks!
- Mike

I don't know enough about TI-99/4a culture to suggest anything but all of those uses sound great!

Were real time clocks common/useful on expanded TI-99/4as?

One other thought...probably from left field so don't take it seriously if it's in any way difficult. I know these computers generally have RAM soldered in. It's damn hard to replace. It's also hard to diagnosis if RAM is the problem with a non functioning machine. Would it be feasible to have RAM on board the cart to substitute the RAM in the computer simply by flicking a dip switch. Partly like PetVet? Might bring quite a few working versions back to life or at least confirm a RAM issue.

Tez

Ksarul
March 8th, 2014, 05:40 AM
Note, one of the major issues to design of a TI multicart is the fact that a significant number of the TI carts contain GROM. GROM is unique to the TI--and it has its own 13-bit internal auto-incrementing address register that it uses to present the next byte of data to the data bus. Tursi has designed a GROM implementation using the ATMEL1284 that allows up to 128K of GROM, along with a lot of other functions that may be of use here. The current version of the board that uses it has some lingering issues (it intermittently crashes the TI, even without the chips installed (but with all resistors and capacitors), which makes me think it may be an electrical issue on the board itself).

Here are the files for the board in ExpressPCB (I can send you a couple bare boards to experiment with if you like, Mike), and the WIP manual for it. I have the programming file for the 1284, but I'd have to send that privately.

Ksarul
March 8th, 2014, 05:51 AM
I like the idea, Tezza, but the cartridge port only accepts memory in the >6000 space and in the spaces for GROM 3,4,5,6 and 7 (although one could use up to 16 GROM bases here, so you could actually have up to 80 GROMs of 6K to 8K each attached to the cartridge port (up to 640K of GROM, but no device yet made for the TI goes above 128K in this space). The board I put up in my prior post will also bank switch 512K in 8K increments in that >6000 space (this is separate from the GROM space). The main problem with the TI's onboard memory is that only 256 bytes of it belong to the CPU--the 16K that is also in the console belongs to the VDP. If it goes, you get no display (or a garbled display).

Ksarul
March 8th, 2014, 05:55 AM
Mike--all of the ideas are good--and if you can bring any of them to fruition, a lot of TI folks would be really pleased! Many have asked for the SD-floppy emulator in a cart solution, many have asked for multi-carts, I hadn't thought of using it as a transfer method to preserve cassette-based programs, but that would be an outstanding use as well.

gubbish
March 11th, 2014, 10:14 AM
Ksarul, thanks very much for the PCB files! Will look over them shortly. I think I have some Atmel 1284s around,
I'm still attempting to understand how the GROMs work in the TI. If the GROM has an auto-incrementing address register, does that mean that it presents that address value on the TI address bus, and then 'writes' its value to the data bus, as opposed to having an address presented as you would with a regular ROM? Reading through some of the TI-99 technical resources posted on the AtariAge forum, which look quite useful. Just trying to get a handle on the exact interaction of the GROM with the rest of the machine. The PET memory map seems quite simple in comparison!
Also like the idea of the RAM replacement/expansion, would be great except for the fact as mentioned that the cartridge slot only gets, I believe, 13 of the 16 address lines. Might be possible to have a separate connection to the expansion connector to combine the functionality.
So, still plugging away on this.. Ksarul, I would be very interested in a bare board to experiment with if you have any to spare. Thanks very much, just send me a PM at your convenience and we can arrange it.

Lurch666
December 22nd, 2014, 03:25 AM
Been looking for such a solution myself. This is what I found a while back:

http://webpages.charter.net/nanopeb/

Bad news is that it seems to be our of production and the best bet on getting one is Ebay :(



-- RP


This has just popped up on my ebay saved search (the search was for schmutzig1952).It looks like a stealth listing for a nanopeb.Bought one but now the listing has disappeared.
Did anyone else manage to grab one or was it just for the one?
Anyway looks like I'm going to be digging my TI out again.