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TI-99/2 questions


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#1 mizapf OFFLINE  

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Posted Sat Apr 14, 2018 4:17 PM

I think it is about time to complete the 99/2 emulation in MAME. I have some questions about that machine:

 

1. The specs say that the machine has 32K ROM. All dumps that I know have 24K. That is, we probably need to re-dump the ROMs. Those of you who have a console: Does it look like it has 24 or 32 K ROM? (3 or 4 EPROMs)

2. The console has 4.2 K RAM and can be expanded by 32 K. How is that done? Expansion cartridge? Sockets on the PCB?

 

 



#2 kl99 OFFLINE  

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Posted Sat Apr 14, 2018 11:06 PM

Hi Michael!

I can use my 99/2 today if it helps. Here is my disassembled unit:

http://www.ti99.eu/?...id=3353&lang=en

I have the HX5102 to load any assembler code from disk.

Also I can do continuity tests with my multi meter to identify some connections.

 

There is some bank switching to get to the last 8K Rom.

Some documents from the beginning of the project might tell different, but they couldnt fit the ROM in the targeted memory space for the ROM, so they had to expand the area somehow. Because the decision was done late, they piggypacked the eproms.

 

The Memory Expansion was always planned via the large back bus, which is also used as port to connect potential Cartridges.

And weren't there some plans for a Hex-Bus Memory Expansion?


Edited by kl99, Sat Apr 14, 2018 11:06 PM.


#3 kl99 OFFLINE  

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Posted Sun Apr 15, 2018 12:15 AM

afaik this is the complete list of documents currently available:

http://www.ti99.eu/?...id=2732&lang=en



#4 mizapf OFFLINE  

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Posted Sun Apr 15, 2018 3:37 AM

Klaus, you don't happen to have an EPROM reader? This would make things much easier, and as I saw on some pictures, the circuits are socketed.

 

I can try to write some dumping programs, but it will be a bit more cumbersome as with the 99/8 because of the limited RAM space.



#5 kl99 OFFLINE  

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Posted Sun Apr 15, 2018 3:55 AM

I have to say no to desoldering the eprom from the unit and wiring. it is not just socketed.

http://www.ti99.eu/?attachment_id=3165

 

An assembler program further has the advantage that it can be run on multiple units to identify diffs in the rom from unit to unit.



#6 mizapf OFFLINE  

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Posted Sun Apr 15, 2018 3:58 AM

OK, if not socketed, keep it in the board, sure. I thought I saw a picture somewhere with sockets.

 

Edit: On your pictures, the EPROMs are clearly in sockets, aren't they? (Those with the stickers, type 2564. BTW, you should stick something on those glass windows, or you will risk the EPROM contents to be erased by UV radiation.)

 

I mean, you can certainly keep everything as is, I don't want you to break anything. My only problem is that I do not have a working emulation of the 99/2, so it will be a bit more difficult to write a program and to test it.


Edited by mizapf, Sun Apr 15, 2018 4:27 AM.


#7 mizapf OFFLINE  

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Posted Sun Apr 15, 2018 4:20 AM

Seems as if the anonymous FTP issue with WHTech is not yet fixed.



#8 ti99iuc OFFLINE  

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Posted Sun Apr 15, 2018 5:35 AM

I would want to be useful in something for this project but my two TI-99/2 have a non working keyboard :( and in addition them are also early prototypes.

the Kl99 one is instead one of the latest producted i think and fully working.
anyway if you mizapf thinking that i could do something useful i am ready to start :)


Edited by ti99iuc, Sun Apr 15, 2018 5:35 AM.


#9 mizapf OFFLINE  

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Posted Sun Apr 15, 2018 5:39 AM

Hi Ciro,

 

maybe you can still dump the ROMs - if they are socketed and if you have an EPROM reader. We could then compare the ROM contents from different consoles (just like we did with the 99/8).



#10 mizapf OFFLINE  

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Posted Sun Apr 15, 2018 6:16 AM

There are two statements about the BASIC subprograms: One says there are subprograms CALL PEEK, CALL POKE and CALL MCHL (BASIC Reference manual), while another one lists CALL INIT/PEEK/LOAD/LINK (Software Specification, section 4.2.2). The former version means we would have to include the machine language program as DATA lines in the BASIC program, the latter one would allow for a loader.

 

Klaus, could you please try which one is supported?

 

Also, do you have lowercase letters or not? I found one specification with lower case (Misc BASIC info).

 

We have dumps as PDF on WHTech, but I think it will be a pretty hard job to OCR them back to a binary file. Mabe someone wants to try?



#11 ti99iuc OFFLINE  

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Posted Sun Apr 15, 2018 6:22 AM

Yes i have the EPROM reader and them are socketed but not easy to read, at least one could.

Attached File  1.png   243.74KB   2 downloads

there are also two of these but probably we do not need to read or not seems to be EPROMS:

Attached File  2.png   186.1KB   2 downloads

maybe the right way should be the same we done on the TI-99/8 dumping using the Floppy Driver and in this case KL99 have a fully working system.
I Should try to fix the keyboard or find another way to connect a keyboard.
Fabrice Montupet offered his help on this but need time anyway.

#12 ti99iuc OFFLINE  

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Posted Sun Apr 15, 2018 6:25 AM

I have to say no to desoldering the eprom from the unit and wiring. it is not just socketed.
http://www.ti99.eu/?attachment_id=3165
 
An assembler program further has the advantage that it can be run on multiple units to identify diffs in the rom from unit to unit.


Klaus but didn't you already dumped the Roms ?

http://www.ti99.eu/?...id=3376&lang=en

Edited by ti99iuc, Sun Apr 15, 2018 6:27 AM.


#13 kl99 OFFLINE  

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Posted Sun Apr 15, 2018 6:55 AM

There are two statements about the BASIC subprograms: One says there are subprograms CALL PEEK, CALL POKE and CALL MCHL (BASIC Reference manual), while another one lists CALL INIT/PEEK/LOAD/LINK (Software Specification, section 4.2.2). The former version means we would have to include the machine language program as DATA lines in the BASIC program, the latter one would allow for a loader.

 

Klaus, could you please try which one is supported?

 

CALL PEEK, CALL POKE, CALL MCHL are in the Subprograms List of the Basic Interpreter. Can be verified by checking the R1 dump file (C2000-C3FF).



#14 kl99 OFFLINE  

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Posted Sun Apr 15, 2018 6:57 AM

Also, do you have lowercase letters or not? I found one specification with lower case (Misc BASIC info).

 

http://atariage.com/...p/#entry3618943

in short: includes small caps letters.



#15 kl99 OFFLINE  

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Posted Sun Apr 15, 2018 6:58 AM

Klaus but didn't you already dumped the Roms ?

http://www.ti99.eu/?...id=3376&lang=en

 

Yes, via some Basic Program, that peeks every byte of the memory.

However there is a hidden bank that is only activated instead of another when some CRU code is sent.



#16 kl99 OFFLINE  

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Posted Sun Apr 15, 2018 7:03 AM

We have dumps as PDF on WHTech, but I think it will be a pretty hard job to OCR them back to a binary file. Mabe someone wants to try?

 

I did some manual comparison of the three banks I made dumps of with those print out and they fully match.

Interesting will be to have the diagnostic ROM available, also for emulation.



#17 mizapf OFFLINE  

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Posted Sun Apr 15, 2018 7:15 AM

Ah, thanks for reminding me of that thread. If you take my message from there, saying that Hexbus is still in the queue, you will notice the difference to now: The Hexbus has been done. Thus ...

 

Yes, the point is that one ROM is still missing. My suggestion would be to create a small machine language program that turns on the ROM, copies a portion of it into RAM, and then dump it the same way as the other dumps were done. If necessary, we can do it in small portions of 1K. Or 512 bytes?

 

When I look into the MAME code, it seems to me as if the second ROM bank is turned with the S0 keyboard line. I can try to figure it out by disassembling the existing ROM. I have a strong feeling that the key to find out how to turn on the ROM is not inside the missing ROM. ;)



#18 fabrice montupet OFFLINE  

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Posted Sun Apr 15, 2018 1:49 PM

The ROMs of my 99/2 prototype aren't fast to pick up. To read them with my EPROM programmer, I before have to desolder all the piggy back chips and the strap wires. But If it is the only solution , I can do that.

ti992_1.jpg

 

ti992cm1.jpg



#19 acadiel OFFLINE  

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Posted Sun Apr 15, 2018 9:10 PM

If there are three 2564's, isn't that 24K?  Where does the other 8K live?

 

I emailed someone who I know had a 99/2.... just to see what they had anything on it like dumps, etc.  This person would likely have had it if they were available.



#20 kl99 OFFLINE  

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Posted Mon Apr 16, 2018 12:17 AM

The prototype of Fabrice is an earlier version, not the 32k version.

Here are the 4 eproms on mine:

http://www.ti99.eu/?attachment_id=3149



#21 fabrice montupet OFFLINE  

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Posted Mon Apr 16, 2018 4:53 AM

Yes, my 99/2 is a  very early version.  Its ROM could be interesting to read. It is the reason why I proposed to study them.



#22 mizapf OFFLINE  

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Posted Mon Apr 16, 2018 5:32 AM

Hi Fabrice, we may find a way to dump the ROMs without desoldering, and it will certainly be interesting to get a dump from yours.

 

I think I already figured out how to turn on the missing bank: setting bit 0 on CRU base E000. But if you only have 3 EPROMs there is most likely no second bank.

 

Klaus has a dump program in 99/2 BASIC that can save the data to disk; maybe you can get it from him.



#23 kl99 OFFLINE  

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Posted Mon Apr 16, 2018 8:07 AM

the program is just a few basic lines which can be seen in the rom dumping video



#24 mizapf OFFLINE  

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Posted Mon Apr 16, 2018 8:43 AM

OK, looks pretty simple. Klaus, could you please check the first available machine code location by doing a CALL PEEK(-4086,A,B) and report it here? (see personal message)

 

I need to know this to find out how much buffer we can use for copying the second bank. The longer we can get it, the less passes we need for saving the contents.

 

The machine code itself is only 26 bytes.



#25 retroclouds OFFLINE  

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Posted Mon Apr 16, 2018 10:49 AM

Klaus I watched the video and I'm really surprised by the speed of the Basic interpreter. 
Seems a lot faster than on the TI-99/4A. I just did a quick test and took the same program, but without saving to disk.
From that alone I would say, that on the TI-99/2 it's probably 2,5x - 3x times as fast as in Extended Basic on the TI-99/4A.

Edited by retroclouds, Mon Apr 16, 2018 10:49 AM.





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