1040 STF 6 chip to 2 chip TOS 1.04 conversion

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1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Wed May 10, 2017 11:43 am

Hello,

I couldn't find this in the stickied posts or via search, hope I'm not reinventing the wheel...

I have a Rev D 1040 STF with 6 chip 1.0 TOS. I was gifted a 2 chip 1.04 TOS from someone who burned an extra set.

My board doesn't have the 256/1M solder pads (or if it does, they're unlabeled).

I'd like to know if it's possible to go to a 2 chip TOS - I have lots of vintage/retro computers and am very comfortable soldering, modding, etc.

All of the guides I could find via google are on long-dead web pages.

Can anyone point me to a way to do this without purchasing adapters, etc? Is it possible?

Thank you!

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Wed May 10, 2017 1:30 pm

I believe you'll have to merge the three ROMCS signals into one. I recall doing something similar to this years ago, but unfortunately I don't recall any details. It most likely involved some diodes to form an OR gate, and some extra wires to bring the missing address signals to ROM sockets.
If I would do that again, I would bring the three ROMCS signals (/ROM0, /ROM1 and /ROM2) together through Schottky diodes (BAT54), resulting signal will need a pull-up (something like 4k7) and it will go to the /CS signal of the two new TOS ROMs. Then some extra wires for missing address signals, of course new sockets, and you should be ready to go.
Some info here: http://www.atari-forum.com/viewtopic.ph ... 9&start=25

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Greenious » Wed May 10, 2017 8:14 pm

Well, it's not that hard if you know what you do.

As Kubik wrote, you need an or-gate to combine the 3 ROM-CS signals into one. Also, you need to feed A16 & A17 to the 2 eproms for it to work. (which are the 3 solderpads available on later STs)

But a 2-EPROM TOS set uses 32 pin EPROMs, and the sockets in the ST is 28 pin... (Atari's own 2 chip TOS came on 28 pin 1mbit mask-roms)

So you need to fix that aswell.

Some info can also be found here: http://atari4ever.free.fr/hardware/zip/tos104up.zip

http://dev-docs.atariforge.org/files/10 ... 6-1987.pdf
And page 4 in the PDF shows the solderpads in later ST's, the pinouts of the ROMs and how it generally works.
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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Wed May 10, 2017 8:54 pm

Thank you both! Very informative.

I hadn't even noticed that the 1.04 EPROMS were 32 pin...

If I understand the text file included in the .zip: He's performing the upgrade from 28 pin to 32 pin but in a 2 EPROM system, so he didn't have to do (or document) the signal combining you both discuss?

In order to combine the signals, I would build an OR gate out of diodes similar to this:

Image

Connecting ROM 0,1,2 to the anodes of the diodes, tie the cathodes together, through the pullup resistor and connect to /CS on the new roms. I don't see /CS labeled in the text file, is that the same as /CE?

Anything I'm missing?

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Greenious » Wed May 10, 2017 10:11 pm

Personally, I would use a 74LS or gate, but diodes work aswell I guess.

CS/CE, or Chip Select/Enable (usually) is the same, yes.
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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Wed May 10, 2017 10:57 pm

Sorry for all the questions, but I'm trying to learn digital logic.

So something like this, then?

Image

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Greenious » Wed May 10, 2017 11:38 pm

That'll work.
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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Thu May 11, 2017 11:18 am

Actually, 74LS11 would be better, that's what's used on newer ST mainboards to do the same trick. Diodes might be easier to cram into the board, and I usually have plenty of those.

As for the "bigger sockets", what I usually do is covering the mainboard under the extra pins with some Kapton tape and bending those extra pins outwards. That way, you can solder them easily and still there's no risk in shorting out something on the board.
Kapton tape is made of plastic that withstands the soldering temperature. I think Kapton is a marketing name, the material itself is called "polyimide"

Edit: I just realized 74LS11 is AND gate, not OR - sorry. My previous post was wrong, you need AND gate - if at least one input is low, the output has to be low too.
Image

Another edit: you might consider using 74HCT11 if you can't get 74LS11. Avoid 74HC11. If going for the diodes, use Schottky diodes like BAT54. Traditional 1N4148 will probably work too, but their "logic low level" might be too high.

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby AtariZoll » Thu May 11, 2017 11:32 am

ROM CE signals are low active, so you need to use actually AND instead OR. Still possible with diodes, just need to reverse them - so cathodes to A,B,C, and use pull-up resistor.
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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Thu May 11, 2017 12:35 pm

You all are the best! Thanks for sharing your knowledge.

Just to clarify, if I use diodes, the pull-up resistor connects the anodes of the diodes to /CE on both EPROMS?

And if I use an AND gate the pull-up resistor connects the output to /CE, and I also have to connect power and ground on the gate?

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Thu May 11, 2017 1:37 pm

The pull-up connects anodes to 5V ("+Es" here means 5V). The anodes also go to the /CE on both EPROMs. Look at the picture above - the "Out" goes to /CE signals of EPROMs. In your case, you will use three diodes, for /ROM0, /ROM1 and /ROM2.

The idea is that if both In1 and In2 are at high level, the diodes don't conduct, and the pull-up resistor keeps the "Out" at high level.
If at least one of In1 / In2 is low, the corresponding diode conducts, thus its anode will be at low level too (actually, at ~0.5V). The pull-up resistor isn't "strong" enough to keep the output at high level any longer, thus the Out voltage will be set by the voltage on the anode of the conducting diode. The pull-up resistor must have the "right" value, not too high, not too low. If it's too low, it wastes a lot of power and stresses or even damages the logic connected to In1 and In2 inputs. If it's too high, it might not be able to provide enough "juice" for the Out output, and might also slow down the whole thing, making it miss some input signals. Typically, 4,7 KOhm (4k7) is a good compromise. You can go down to 2,2 KOhm.

With AND gate, you don't need the pull-up resistor, the output of the gate will be connected directly to the /CE pins of EPROMs. Of course you have to connect power and ground, and also add a ceramic capacitor across the power/ground pins of the gate. 100nF (0.1uF) is enough. If you will use HCT gate, tie all the unused inputs to ground - there are three gates in one 74HCT11 and you will need just one gate. Outputs of those unused gates can be left unconnected.

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Thu May 11, 2017 1:44 pm

Excellent. Now I have a plan.

Once I acquire the necessary parts and do the upgrade, I'll post back here with pictures and (hopefully positive) results.

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Thu May 11, 2017 1:55 pm

Good luck! Next thing will be 4MB memory update, I presume :)

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Greenious » Thu May 11, 2017 8:15 pm

Kubik wrote:Edit: I just realized 74LS11 is AND gate, not OR - sorry. My previous post was wrong, you need AND gate - if at least one input is low, the output has to be low too.


Good catch, I didn't reflekt at all over the OR gate... :thumbs:

Kubik wrote:Good luck! Next thing will be 4MB memory update, I presume :)


Actually, if I might recommend a mod, it would be the Lacescan overscan mod. It's one of the coolest ST mod you can do imho.
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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Mon May 15, 2017 9:05 pm

Kubik wrote:With AND gate, you don't need the pull-up resistor, the output of the gate will be connected directly to the /CE pins of EPROMs. Of course you have to connect power and ground, and also add a ceramic capacitor across the power/ground pins of the gate. 100nF (0.1uF) is enough. If you will use HCT gate, tie all the unused inputs to ground - there are three gates in one 74HCT11 and you will need just one gate. Outputs of those unused gates can be left unconnected.


I've sourced a 74LS11 and capacitor, pulled the ST apart and figured out where the rom 0,1,2 signals are and which bank is Hi/Lo.

Do I bend pin 22 (/CE) upwards on each eprom and connect them to the gate output? Or do they get inserted into the sockets and connected to the gate?

Using a 74LS11 do I need to tie the unused inputs to ground?

Thank you, warming my soldering iron up ;-)

EDIT: Got the EPROMS prepped

Image

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Tue May 16, 2017 9:12 am

You have to bend the /CE signals upwards and connect them to the gate output. The socket already has /CE, but not the one you want (it will be /ROM0, /ROM1 or /ROM2, depending on the socket you use, but you need all of them combined).
74LS11 doesn't really need to do anything special to unused inputs. If you want to be on the safe side, tie all the unused inputs together and then connect them via 1KOhm resistor to +5V, but it's not necessary. You can also tie them to ground, but that will introduce slightly higher power consumption (a few miliamps only).

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Tue May 16, 2017 12:06 pm

Well, something isn't right...

I wired everything up and tested. I get a power light, one click from the floppy drive, and a white screen - no boot. I made sure no wires or pins are shorted.

These are abbreviated instructions from the .zip that Greenious posted:

Code: Select all

   ROM TOS 1.0/1.02                     EPROM TOS 1.04
     (Worked by me)                    (Thanks to ChipDir)
    +------\/------+                    +------\/------+         
 1 -|A15        Vcc|- 28            VPP |1           32| VCC     
 2 -|A12        A14|- 27            A16 |2           31| /PGM   
 3 -|A7         A13|- 26            A15 |3           30| NC       
 4 -|A6          A8|- 25            A12 |4           29| A14     
 5 -|A5          A9|- 24             A7 |5           28| A13     
 6 -|A4         A11|- 23             A6 |6           27| A8     
 7 -|A3         A16|- 22             A5 |7           26| A9     
 8 -|A2   ROM   A10|- 21             A4 |8   271001  25| A11     
 9 -|A1         /CE|- 20             A3 |9           24| /OE     
10 -|A0          D7|- 19             A2 |10          23| A10     
11 -|D0          D6|- 18             A1 |11          22| /CE     
12 -|D1          D5|- 17             A0 |12          21| D7     
13 -|D2          D4|- 16             D0 |13          20| D6     
14 -|gnd         D3|- 15             D1 |14          19| D5     
    +--------------+                 D2 |15          18| D4     
                                    GND |16          17| D3     
                                        +--------------+       

bend upwards the pin 2 and 24
Well, take a wire from pin 24 to pin 16.
Now wire together pin 1,32,31 and 30.

Take a short wire (about 2-3 cm) from pin 22 of the old socket, where there
were the ROMs.               
Remember the wire from pin 22? Solder it to pin 2 of the corresponding eprom


And the ROM schematic from a REV C (mine is a REV D):

Image

This is what's going on under the chips:

Image

And this is how everything is connected together:

Image

I took power from the floppy connector for the 74LS11, confirmed I have +5 volts to the chip.

I'm thinking, based on the schematic, that the point I chose for ROM0 (pin 20 of socket U4 - H0 ROM) may not be correct?

Can you folks review and tell me where I went wrong?

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Tue May 16, 2017 12:21 pm

Just one thing - are you sure your EPROMs are programmed right? Upper/lower half, offset etc?

If I am not mistaken, you need to split the TOS to even/odd (high/low) images, and then burn them so that the images are located at the beginning of the EPROM (image is 96KB, EPROM is 128KB).

EDIT: I am not sure if you can take A16 from where you're trying to. What if you try to get A16 from CPU directly?

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Tue May 16, 2017 12:57 pm

Kubik wrote:Just one thing - are you sure your EPROMs are programmed right? Upper/lower half, offset etc?

EDIT: I am not sure if you can take A16 from where you're trying to. What if you try to get A16 from CPU directly?


I don't have any way to confirm the EPROMS are programmed right, however, the person who gave them to me had 2 sets made in case he messed up the install. His set is working properly.

I checked A16 with a multimeter and all of those lines are connected to each other in each bank (Hi vs. Lo), but not across banks. The instructions tell you to grab A16 from the same socket that you're putting the ROM in, so I assumed (possibly incorrectly) that this would work. I can also try grabbing it from the CPU.

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Tue May 16, 2017 6:39 pm

Kubik wrote:EDIT: I am not sure if you can take A16 from where you're trying to. What if you try to get A16 from CPU directly?


Same result if I take A16 from the CPU to both EPROMS pin 2 - White screen, power led, one "clunk" from the floppy drive, then nothing.

EDIT: I notice in exxos 6 chip to 2 chip kit, he also takes A17 from the CPU

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Tue May 23, 2017 10:07 pm

BUMP!

Any of the Atari wizards in this forum have any insight on where my problem may lie before I disassemble everything and return to TOS 1.0?

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Wed May 24, 2017 8:00 am

Does the floppy do the same sound when you just reset the computer? What kind of diagnostic tools do you have?

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Wed May 24, 2017 12:36 pm

Yes, just one "clunk". I have a multimeter, a logic probe, and a lot of patience ;-)

Edit: oops - I lied. I just tried and pushing the reset button does nothing (that I can see or hear)

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby Kubik » Wed May 24, 2017 9:08 pm

As a first check, I'd verify the EPROMs are getting /CE signals, because at the moment it looks like the system doesn't start at all. It would be great if your probe was able to count the pulses as well, that way we could determine what's going on.
I love my Superprobe, it helped me a lot many times. You could even buy it as a kit: http://www.talkingelectronics.com/proje ... eMkII.html
You could also get Sealeae (?) USB logic analyzer, your average Chinese online shop sells them for peanuts.

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Re: 1040 STF 6 chip to 2 chip TOS 1.04 conversion

Postby xnlekf0987 » Thu May 25, 2017 8:44 am

I have a cheap elenco logic probe, but I'm willing to pick up additional troubleshooting tools because I'd like to learn and I have other machines in need of repair.

I checked the CPU CLK and verified I have a pulse. RESET is high and goes low when I press the reset button.

I checked the output of the gate and I see high on the pin connected to /CE on the eproms. I get one pulse on that pin when I press the reset button.

Because my eproms are under the power supply, I'll have to work out some way to rearrange things to power the board if I need to probe the eproms directly.


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