What's inside the TI Extended Basic module?

[Lios]

So I more recently dusted off my TI 99/4a, made a cable for my TI Program Recorder and had some fun messing around with transferring over cassette recordings of TI Basic games. Of course, I'm extremely limited on what I can do without an Extended Basic cart. I was wondering, what all is inside of one and could it be easily replicated with off the shelf components, a proper donor cart, and an eprom? Would it be possible to simply swap out the TI Basic rom (assuming it's contained as such) with an eprom with the XB code on it? I've spent a good long while searching for information on this, and have come up woefully short on even a measly list of components inside the XB cart. I'm kind of surprised no one seems to have at least proposed the idea of hacking in XB functionality before. Any insight is greatly appreciated.

[+Ksarul]

This is not a trivial experiment. There is a way to put the XB functionality into the console--but it requires something called a Zeno Board (and I haven't seen one of those available for sale in a long time, although I do have one for one of my systems). The cartridge has five chips in it that you will not be able to get anywhere else (the GROMs) and two ROM chips. GROMs are specialized ROMs that you cannot replace with a standard EPROM, as the chip has an auto-incrementing 13-bit address register in it. Your computer talks to it as if it were a device, not as memory, per se. It increments and presents the next byte of data on the data bus when selected (although all 8 GROMs in the system advance in lock step and only the one selected presents data). Look at the 512K cartridge threads in the TI Programming subforum and you will get lots of info on how this works amd what current projects are afoot that simulate those GROMs successfully. BTW, there are new cartridge boards out there too--ones that have the capability to emulate an Extended BASIC cartridge and a lot more. I designed the hardware, Tursi designed the software, and Acadiel did most of the hardware testing. I've also got ROM-only boards with space for up to 512K of code--and there are a lot of ROM-only cartridges that it can be used for. I'll be working on soldering the basic components onto a bunch of each of these board types after I finish up here. . .I don't have an EPROM burner set up though, so others have to get chips and do the chip programming on them (the GROM board uses a 512K PLCC Flash chip and an ATMEL ATMega1284P, while the ROM board uses any DIP EPROM from 8Kx8 to 512Kx8.

[Lios]

What a speedy reply! I took a quick skim over your 512k cart thread. There's certainly no lack of in depth info on the subject. I'll have to give it a more thorough reading when I'm better rested. I'll have to check if my eprom burner supports the ATMEL ATMega1284P, because if it does, that GROM board you're working on looks nifty. I don't suppose you've figured out pricing for these boards yet, sans ATMEL and flash chips?

[+Ksarul]

Boards from the current run are $20 assembled. That includes a pair of blank Flash chips (I got a really good deal on them a few years ago), but not the ATMega. Shipping in the US is about $3, so the total cost would be $23, shipped. I built and tested six of them today, so I have a few spares right now. I also have a couple of the ROM-only boards that use DIP EPROMs. I can let you have one of those for $12 assembled (that would be $15, shipped), as I was able to find a less-expensive board house to do the bare boards for them. Note, the board won't have an EPROM yet. Obviously, shipping to locations outside the Continental US would be more.

Edited April 25, 2014 by Ksarul

[Lios]

As tempting as the GROM board is, I don't think my getting on 8 years old, made in china programmer is going to be of much use with the ATMega. I don't suppose the GROM board can function as rom-only without the ATMega in place? Otherwise, I may have to take you up on the offer for the ROM-only board. I assume you take Paypal?

Edited April 26, 2014 by Lios

[+Ksarul]

The UberGROM works as pure ROM only, pure GROM only, or a mix of the two. It is highly flexible (as the manual in the 512K cartridge status thread shows). I do take PayPal. I know Tursi is working on a loader for the UberGROM to load programs into GROM space with it, but I'm not sure if it requires the basic GROM simulator code to be present beforehand (it is still a WIP with no hard-fast schedule as he's working this project in his limited spare time). Gazoo has done a module image to put into it, but we haven't tested the image for full functionality yet, as we haven't put it into the hardware--all tests were done using Tursi's Classic99 emulator.

 

The real difference between the UberGROM (on the ROM side) is that it uses 32-pin PLCCs instead of DIP EPROMs. The 512K ROM-only board will work with anything from 8Kx8 to 512Kx8, all jumper selectable. The UberGROM expects a 512Kx8 chip, but as the addressing for the 256Kx8 and the 128Kx8 match otherwise, it will work with them too.

[Lios]

I have a 32-pin PLCC to DIP adapter for my burner, so programming one is no issue. I'd prefer flash over eprom anyways, saves time on erasing the chips. Simply using it as a rom cart for the time being is enough of a toy for me while I figure out how I want to handle acquiring the ATMega. $23 for an UberGROM + a pair of blank flash chips sounds good to me, even if it is a prototype. What's your paypal?

[+Ksarul]

PM sent on the PayPal. The hardware is actually more pre-production than prototype, as it is the third iteration of the board. All three worked, the changes were more to add additional functionality to the basic design as the original iteration gave us some neat ideas on the GROM side that were relatively easy to implement. Tursi has a demonstration of the GROM code in action, but it isn't set up so that it can be used with GROM images outside the ones in the demo yet--that is the function of his in process loader software.

[Lios]

Payment and PM sent back at you. It sounds like I picked a good time to unbury my TI-99 and decide to actually do something with it. I'll probably be performing one of the internal 32k memory upgrades as well. It's just too bad this is a US unit with the composite video out, I'd really love to hook up RGB out up to my PVM, even though the rf alone is some of the cleanest I've seen.

[+Ksarul]

You could always get one of the F18A video chip replacement boards--that would give you VGA out on your TI, along with a slew of other enhancements. . .the device:

 

http://codehackcreate.com/archives/30

 

and his store:

 

http://codehackcreate.com/store#!/~/product/category=0&id=14022176

[Omega-TI]

You could always get one of the F18A video chip replacement boards--that would give you VGA out on your TI, along with a slew of other enhancements. . .the device:

 

http://codehackcreate.com/archives/30

 

and his store:

 

http://codehackcreate.com/store#!/~/product/category=0&id=14022176

 

GOOD ADVICE! It was by far the BEST purchase I ever made for my TI.