TI-99/22 project

[RickyDean]

I've sent an email to the designer of the board asking him about it. Isn't the scratch pad in the vram, if so and we use a pico9918 or another video upgrade, aren't we bypassing the on board sram then? Or in the case of a TI99/4a, the dram?

[+OLD CS1]

3 minutes ago, RickyDean said:

Isn't the scratch pad in the vram

Scratch pad (PAD) RAM is 16-bit CPU RAM at >8000 to >80FF.  It is supposed to be expandable to encompass >8000 - >83FF, but each 256 byte block is mirrored and the convention is to use >8300.  Expanding PAD RAM would be nice, but probably would need to be switchable as there is no telling if programs follow the >8300 convention or >8000, which means a program could place or look for data in the wrong 256 byte block.

[JasonACT]

13 minutes ago, Gary from OPA said:

I would like to see a configuration file on the SD card that could be edited to turn on and off certain features.

That's there already for some things, but not the expansion RAM (CALL EXPOFF can do that though).  The trouble is, however, just turning features on and off via config doesn't make the extra PSRAM available for other things (that's controlled by compile time #defines).

 

I know you want a giant cartridge with 16 banks of GROM, but you'll have to wait for the Pico 2 W / RP2350, because I've run out of RAM on the Pico W / RP2040 chip, for the 2 banks of carts I currently support.

[RickyDean]

7 minutes ago, OLD CS1 said:

Scratch pad (PAD) RAM is 16-bit CPU RAM at >8000 to >80FF.  It is supposed to be expandable to encompass >8000 - >83FF, but each 256 byte block is mirrored and the convention is to use >8300.  Expanding PAD RAM would be nice, but probably would need to be switchable as there is no telling if programs follow the >8300 convention or >8000, which means a program could place or look for data in the wrong 256 byte block.

That's right, that is the purpose of the ram chips on the ti, close to the CPU, forgot about that. 

[Gary from OPA]

13 minutes ago, RickyDean said:

I've sent an email to the designer of the board asking him about it. Isn't the scratch pad in the vram, if so and we use a pico9918 or another video upgrade, aren't we bypassing the on board sram then? Or in the case of a TI99/4a, the dram?

Looking at the schematic, the dip switches control it they can disable 2000 / a000 / c000 / e000 / 8000 so the first 4 switches can turn off the 32k onboard, the last switch turns off the scratch pad which is shared with the 32k.

 

The vdp static ram chip not used, in our case with pico9918 we don't it or the two support chips latching the data bus.

[Gary from OPA]

13 minutes ago, OLD CS1 said:

Scratch pad (PAD) RAM is 16-bit CPU RAM at >8000 to >80FF.  It is supposed to be expandable to encompass >8000 - >83FF, but each 256 byte block is mirrored and the convention is to use >8300.  Expanding PAD RAM would be nice, but probably would need to be switchable as there is no telling if programs follow the >8300 convention or >8000, which means a program could place or look for data in the wrong 256 byte block.

Yes, there is a few ti99 original cartridges that sadly write to 8200 instead of 8300 for some weird reason. All tho it would be nice to have it software configurable to have expanded 1k ram as option, the way he has used the two 32k chips it could be done easy enough, there a lot of wasted ram there since it's really 64k but only 32k plus 256 bytes is used. Crazy.

 

Also the rom chips he does have it setup with jumpers as you can have two console ROM OS with the dual 27c64 as that is 16k total and the jumpers select either top 8k or bottom 8k.

 

Plus if using the the actual 9918 vdp, you have 32k of gram instead of 16k, but he has it tied to only use half the chip, there could be added cru bit allowing for two banks of 16k vfp if using original 9918 instead of F18A or pico9918

[Gary from OPA]

18 minutes ago, JasonACT said:

That's there already for some things, but not the expansion RAM (CALL EXPOFF can do that though).  The trouble is, however, just turning features on and off via config doesn't make the extra PSRAM available for other things (that's controlled by compile time #defines).

 

I know you want a giant cartridge with 16 banks of GROM, but you'll have to wait for the Pico 2 W / RP2350, because I've run out of RAM on the Pico W / RP2040 chip, for the 2 banks of carts I currently support.

Yes, it's shame. Off topic but looking forward to what can be done with the pi pico 2 w. As current one requires like you said recompile firmwares to make changes. Still waiting for my pi pico 2 to arrive from UK, hopefully someday but maybe never since the Canadian government lists raspberry pi as hacking devices so they rarely get through customs now.

[nuxi]

1 hour ago, Gary from OPA said:

Looking at the schematic, the dip switches control it they can disable 2000 / a000 / c000 / e000 / 8000 so the first 4 switches can turn off the 32k onboard, the last switch turns off the scratch pad which is shared with the 32k.

 

Can't see that I would get much use from this. Think I might tie them together and pull them out to an external switch.

1 hour ago, Gary from OPA said:

Plus if using the the actual 9918 vdp, you have 32k of gram instead of 16k, but he has it tied to only use half the chip, there could be added cru bit allowing for two banks of 16k vfp if using original 9918 instead of F18A or pico9918

Now that could be fun to play with...

[stevee671]

You all talk about the openness and space, this board makes a great starting point for improvements:

 

Add Hex-Bus (possible because TI had the interface (i owned one) and was integrated on the 4B and 5)

Add Speech (can be done as well)

Integrate Pico9918 or F18A with a VGA port on the back of the Motherboard

Maybe TiPi integration

 

Place all ports at the rear of the system

 

[RickyDean]

Yeh, I can choose the pico9918, or a tang9k with HDMI, or a F18a, or my TIM 9958 upgrade from OPA as video, and maybe even a TAng 20k 9938 upgrade.

I have the Pico sidecar designed by JasonACT, that gives disk, rom/grom, 32k/SAMS/MYARC/FOUNDATION 512k capabilities, bluetooth keyboard,/joystick, wifi, as well as the possibiltiy of Tipi or Apedsk99, or other.

 

Oh the possibilities are endless.

I'll probably end up putting this board into an old Kaypro II case I've had for years with the intention of building a portable TI.

Edited August 31 by RickyDean

[+OLD CS1]

30 minutes ago, stevee671 said:

You all talk about the openness and space, this board makes a great starting point for improvements:

 

Add Hex-Bus (possible because TI had the interface (i owned one) and was integrated on the 4B and 5)

Add Speech (can be done as well)

Integrate Pico9918 or F18A with a VGA port on the back of the Motherboard

Maybe TiPi integration

 

Place all ports at the rear of the system

Moving into Ultimate99 (a la Ultimate64) territory.

[stevee671]

6 minutes ago, OLD CS1 said:

Moving into Ultimate99 (a la Ultimate64) territory.

Should we start this discussion on the Development forum and turn this into a real project.

 

I like that name “Ultimate 99”.

[Gary from OPA]

27 minutes ago, RickyDean said:

Yeh, I can choose the pico9918, or a tang9k with HDMI, or a F18a, or my TIM 9958 upgrade from OPA as video, and maybe even a TAng 20k 9938 upgrade.

I have the Pico sidecar designed by JasonACT, that gives disk, rom/grom, 32k/SAMS/MYARC/FOUNDATION 512k capabilities, bluetooth keyboard,/joystick, wifi, as well as the possibiltiy of Tipi or Apedsk99, or other.

 

Oh the possibilities are endless.

I'll probably end up putting this board into an old Kaypro II case I've had for years with the intention of building a portable TI.

The thing about putting too much different things into the motherboard, is not everyone wants the same stuff, and things change over time as new devices get designed.

 

If we going to design an ultimate 99 @stevee671 , I would like to see the motherboard designed in such a way that it's mainly an interface layout with a new backplane onboard, the PEB was great idea, but these days with SMT and such it's over kill.

 

My vision would be compatibility with both worlds still have the 8bit bus out for sidecars and the PEB but on the standalone redesigned 4a motherboard console to reserve an area in the top left corner it could be like addon second board that gives you like at least 4 or if possible 8 slots that are 16 bit bus design, similar to what been done with the homebrew 6502 community with their small HBC-56 boards that plug into a double row pin header, @visrealm would know what I am talking about.

 

Then you have different modules make, depending on what you want, like f18a card or pico9918 or real v9958 card, etc. and 16bit tipi or a 16bit Pico2 or 16bit Sam's, etc.

 

If I have time I will draw up a little drawing of what I am trying to say, you still have the underlying main motherboard with its main parts needed, but another set of bus headers added to place a secondary 16bit bus backplane on the top left corner behind the keyboard and to left of the cartridge ports giving you option of installing custom new cards that others design for the ultimate 99.

[RickyDean]

2 minutes ago, Gary from OPA said:

The thing about putting too much different things into the motherboard, is not everyone wants the same stuff, and things change over time as new devices get designed.

Understood about what you're saying, but we are talking here too about the current board being offered and I am just saying what can be currenly done to it. 

I would definitely love to see a Geneve/TI99 or Ultimate type produced also. But I am also thinking of a few weeks from now too.

[Gary from OPA]

23 minutes ago, RickyDean said:

Understood about what you're saying, but we are talking here too about the current board being offered and I am just saying what can be currenly done to it. 

I would definitely love to see a Geneve/TI99 or Ultimate type produced also. But I am also thinking of a few weeks from now too.

Yes, the current project is good already, it is baseline to start with and will be easier to develop various other things mods for it and at some point a whole new redesign with finalize ideas, it will not come overnight and could take months to complete.

 

First, I need the set of boards in my hand build them up and so continue to work on the new ti99 os using grommy2, because no matter what cool new hardware we design, it needs a ton of backend support to make it a dream to use and program for as well.

 

Plus, the first few mods I want to do, I want to still be able to have someone install them on a original /4a motherboard as well.

 

The "ultimate 99" has to be carefully planned and done in stages, and this 99/22 is great backbone to help design and troubleshoot and try out various custom mods first.

 

[+OLD CS1]

1 hour ago, stevee671 said:

Should we start this discussion on the Development forum and turn this into a real project.

 

I like that name “Ultimate 99”.

I would say start a new thread in the dev forum and let this remain here for people who are interested in the 99/2.

[Gary from OPA]

1 minute ago, OLD CS1 said:

I would say start a new thread in the dev forum and let this remain here for people who are interested in the 99/2.

Good idea.. this thread should stay focused on the actual 99/22 schematics, building, etc.

 

And when the time comes a ultimate 99 development thread can be started.

[nuxi]

5 minutes ago, Gary from OPA said:

Plus, the first few mods I want to do, I want to still be able to have someone install them on a original /4a motherboard as well.

 

The "ultimate 99" has to be carefully planned and done in stages, and this 99/22 is great backbone to help design and troubleshoot and try out various custom mods first.

 

Yeah. I'd agree, the main focus of this project should be a 100% compatible, hackable motherboard with common QoL improvements. And Dan has done an amazing job: it's 90% of what I'd want, anyway.

 

I'd like to see this hit a more-or-less fixed "1.0" spec that other projects can then fork off of.

[stevee671]

Ultimate99 thread created in the Development forum. This thread will stay true to the 99/22.

 

 

Edited August 31 by stevee671

[RickyDean]

Dan got back with me on the memory question.

"

Yup – the DIP switch on the main board allows you to configure which bank areas are populated with RAM.     RAM0 enables RAM to addresses >2000-3FFF (Lo Memory Expansion) RAM1 enables RAM to addresses >A000-BFFF (Hi Memory Expansion) RAM2 enables RAM to addresses >C000-DFFF (Hi Memory Expansion) RAM3 enables RAM to addresses >E000-FFFF  (Hi Memory Expansion) RAM4 enables RAM to addresses >8000-83FF (Normal TI Scratch Pad RAM)   Note that I have never actually tested off-board 8 bit RAM, so this is new territory and might need some debugging 😊   also note that on-board RAM is 16 bit – so all of those external RAM sources will be slower.   Dan

[Gary from OPA]

10 minutes ago, RickyDean said:

Dan got back with me on the memory question.

"

Yup – the DIP switch on the main board allows you to configure which bank areas are populated with RAM.     RAM0 enables RAM to addresses >2000-3FFF (Lo Memory Expansion) RAM1 enables RAM to addresses >A000-BFFF (Hi Memory Expansion) RAM2 enables RAM to addresses >C000-DFFF (Hi Memory Expansion) RAM3 enables RAM to addresses >E000-FFFF  (Hi Memory Expansion) RAM4 enables RAM to addresses >8000-83FF (Normal TI Scratch Pad RAM)   Note that I have never actually tested off-board 8 bit RAM, so this is new territory and might need some debugging 😊   also note that on-board RAM is 16 bit – so all of those external RAM sources will be slower.   Dan

Yes, just as I thought when looking at the schematic a few posts back.

 

So for testing PEB setup or picow sidecar we would disable the first 4 switches but leave the scratch pad on.

 

And I think from looking at it more it might be indeed 1k of scratch pad not just 256 bytes, so that could be an issue with some minor original cartridges that have 8200 instead of 8300, we need to debug that as well.

 

Once I get my board and build I will for sure be giving it a full workout by interfacing it with my dual peb setup with 14 different peb cards all running at once along with the thermal printer and axiom sidecars so this will be fun test.

 

Also because of the expansion port being in the back inside of the right side, having a normal setup of sidecar and dual PEB setup with @Ksarul normal peb joiner, just will not work, angles wise.

 

So i am going to order one of these cables and test it out as well, as I want to see what is best load wise and timing also for testing, compared to my current setup as you can see below.

 

https://iec.net/product/ti994a-side-port-splitter-16-inches/

Edited August 31 by Gary from OPA
added info about dual peb testing, setup.

[RickyDean]

Here's a project to add a tipi internally to the TI99/22.

 

https://github.com/lucedoriente/TI99-4A-internal-TIPI

[Gary from OPA]

6 minutes ago, RickyDean said:

Here's a project to add a tipi internally to the TI99/22.

 

https://github.com/lucedoriente/TI99-4A-internal-TIPI

Nice, I am browsing thru it on my mobile, which doesn't have anything kicad on it of course, but I see nothing in the GitHub that shows what it looks like or how it connects, can someone kindly load the files and take a screenshot of the PCboard what it looks like and how it connects.

[RickyDean]

5 minutes ago, Gary from OPA said:

Nice, I am browsing thru it on my mobile, which doesn't have anything kicad on it of course, but I see nothing in the GitHub that shows what it looks like or how it connects, can someone kindly load the files and take a screenshot of the PCboard what it looks like and how it connects.

Here ya go..

[Gary from OPA]

4 minutes ago, RickyDean said:

Here ya go..

So am I correct in that it designed to plugin on this connector I highlighted in green in the 99/22 board? At the top just to left of the back io port?