Jump to content
IGNORED

Multiple GROM simulator


fabrice montupet

Recommended Posts

My 99/8 computer has a low serial number (#22), it didn't received the Pascal GROM/ROM Kit.
I would like to try this feature. As it will be difficult to find a ROM/GROM Kit, I would like to make my own. No chance for me to produce a GROM, so my idea is to make a hardware GROM simulator that will use EPROM chips and that will use the less component that it is possible to make smallest PCBs. The goal is to install onto the 99/8 motherboard
No need to reinvent the wheel. So, before starting the developpment,I would like to know if someone has already made a GROM simulator that has the abilty to manage 10 GROMs.
Of course, I read many years ago the excelent book of Mike Bunyard about the TI-99 hardware and I was very interested by the GROM simulator that he proposed. But it is only for a 6Kb GROM chip. It could be a start for build my own simulator .
It seems to me that an article about the GROM simulation has been published in the German TI-Revue but I haven't found it.

Do you have any information?

Thanks by advance

  • Like 2
Link to comment
Share on other sites

I haven't begun the study of all the P-System GROMs. But, yes, 5 GROMs per base is normaly the norm.

 

I forgot to mention an important pre-requisite : Not to disfigure the 99/8, I will use only technology that was used in 1983 ( at the 99/8 period). So no Atmel and all other things like that.

  • Like 1
Link to comment
Share on other sites

The maximum memory as shown in MAME:

 

https://github.com/mamedev/mame/blob/master/src/mame/drivers/ti99_8.cpp

 

Speech: TMS5200C, a rare variant of the TMS52xx family. Compatible to the
speech data for the separate speech synthesizer for the TI-99/4A.
Speech ROMs CD2325A, CD2326A (total 128K*1)

ROM: TMS4764 (8K*8 ), called "ROM0" in the specifications [1]
TMS47256 (32K*8 ), called "ROM1" [1]
TMS47128 (16K*8 ), "P-Code ROM" (only available in late prototypes)
See below for contents

GROMs: TI-specific ROM circuits with internal address counter and 6 KiB
capacity (see grom.c)
3 GROMs (system GROMs, access via port at logical address F830)
8 GROMs (Pascal / Text-to-speech GROMs, port at logical address F840)
8 GROMs (Pascal GROMs, port at logical address F850)
3 GROMs (Pascal GROMs, access via port at logical address F860)
(total of 132 KiB GROM)

RAM: 1 TMS4016 (SRAM 2K*8 )
8 TMS4164 (DRAM 64K*1)

 

(I HATE these silly smileys that show up e.g. when you have an 8 and a closing parenthesis)

Edited by mizapf
  • Like 1
Link to comment
Share on other sites

  • 2 months later...

It seems to me that an article about the GROM simulation has been published in the German TI-Revue but I haven't found it.

 

Do you have any information?

 

Hi Fabrice,

 

Did you already find the TI-Revue articles?

I found an article in TI-Revue 5/85, where Heiner Martin published his his GROM module (8k GROM + 8k ROM) schematics and the PCB.

Additionally there are articles in TI-Revue 6/87 (which resides in the magazine HCA). Reiner Zigler tells us there how to build a module expander (a small hardware which generates additional GROM base addres select lines) and how to expand the previously mentioned GROM module to 40k GROM.

Do you need these articles?

Link to comment
Share on other sites

 

Hi Fabrice,

 

Did you already find the TI-Revue articles?

I found an article in TI-Revue 5/85, where Heiner Martin published his his GROM module (8k GROM + 8k ROM) schematics and the PCB.

Additionally there are articles in TI-Revue 6/87 (which resides in the magazine HCA). Reiner Zigler tells us there how to build a module expander (a small hardware which generates additional GROM base addres select lines) and how to expand the previously mentioned GROM module to 40k GROM.

Do you need these articles?

I have the TI Part from the German Magazin HCA as PDF Scan here

HCA_1987_8.pdf

Edited by Flottmann1
  • Like 1
Link to comment
Share on other sites

Not to stray too far OT, but...it makes me wonder about the GROM box TI was taking around to state fairs back in the day. A fair number of unreleased module dumps came our way because they were being shown on these boxes.

 

 

Ksarul is now in possession of the two that I had. I have pictures on http://www.hexbus.comof them :)

Link to comment
Share on other sites

Thank you Flottmann1 :-)

I am going to read it with a great pleasure!

Sorry Fabrice, for my late response, but Flottmann was too "flott" (German slang word for hurry) for me (like back the years in school: "hmmm, hmmm, take me...! I know it better...")

:-)

 

If you still miss some information, just ask... I only have my weekends to be TI-active...

  • Like 2
Link to comment
Share on other sites

  • 6 years later...
7 hours ago, Artoj said:

Hi All,

I am not sure why the 74LS139 pins 4/5/6/7 are not connected to anything and what I can figure they are for adding RAM (6264) on pin 20 (CE#). Can anyone who reads German or who has built the circuit let me know. Regards Arto.

Here is a quick translation of the two paragraphs that discuss the ROM and GROM selection circuitry. Note that the pins you are looking at here are not normally used unless trying to decode the ROM space into 2K chunks. . .

Martin Board.odt

  • Like 2
Link to comment
Share on other sites

37 minutes ago, Ksarul said:

Here is a quick translation of the two paragraphs that discuss the ROM and GROM selection circuitry. Note that the pins you are looking at here are not normally used unless trying to decode the ROM space into 2K chunks. . .

Martin Board.odt 22.94 kB · 0 downloads

Thank you for the prompt reply, I find it curious that this was never explained clearly. I am looking into the GROM circuitry so I can start to write software. What I have gathered so far, is TI created a system that can run programs with a minimum of RAM and a maximum of control. The only loss was speed and a slight increase of complexity. The GPL language is an amazing journey and Speccery has unlocked a lot of it's potential.  I am looking forward to applying this knowledge into programming. Thanks Ksarul for you insight, regards Arto.    

  • Like 2
  • Thanks 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...