Atari 520 STFM - Issue 4x Multi TOS Upgrade

[DigitalSkunk]

Hey guys, I am probably overlooking something silly, but I am a bit stuck.

• I got Petari's awesome TOS Improved 2 versions, and Atari's original TOS 1.04, 2.06
• On 2x 27c4001 EEPROMs
• A17 and A18 (Pin 30, 31) are TOS toggles. This seems to be working. Switch off has both pins at 5v. I used 33ohm resistors I had laying around, is this high enough for protection?
• With both switches grounded, A17 and A18 low, it successfully boots TOS 1.04 original.

I can't get the other three versions to boot, and am not sure what to check next.

I have a strange revision of 520 STFM, ROMs are under the PSU, 2 chip version. So, to be less cramped and reduce the chance of ROMs, GAL shorting to the bottom of the PSU shield, I actually installed the GAL on top of the 68k, and ran a fairly long CE1 line from GAL 15 pin to Pin 22 of new ROMs.

• Pin 24 on new ROMs are pulled up from the socket, connected to GND on mono. (OE)
• Under pin 24, I ran A16 to Pin 2 of new ROMs.
• GAL pin 15 CE1 is running to Pin 22 of new ROMs. This pin is inserted in the socket still.
• When I unsoldered the CE blob jumper on the board, TOS 1.04 original quit working until I soldered it back on 1M pad.
• A16 and A17 pads are still soldered on 1M like stock.

I hope this is enough info to start. Thanks in advance for nay help anyone can offer. I am rather confused at this point. lol

[DigitalSkunk]

I actually ended up completely redoing everything.

I left the original 28 pin ROM sockets in place. I got some rainbow ribbon cables and used some prototype board to move the new EPROMs over to where the factory RAM was previously. I can easily pop in 32 pin ROMs or switch back to the originals for testing by inserting one or the other.

Also put two switches in the area under the keyboard with the joystick ports to avoid drilling any holes in my case, but allow easy TOS version switching without opening the case.


The issue I found was ground on the GAL chip accidentally shorted to another ground area on the board, which I believe was keeping the GAL from operating. (It will worked on the stock ROMs that the GLUE can address, which didn't rely on the GAL chip)

TOS Improved is so cool.... now to figure out storage and a regular backup solution so I can start really playing with my ST

 

[Ronald J. Hall]

I love the later TOS versions. So many features and I love
the single-key keyboard shortcuts.

I've got TOS v2.06 in my Mega ST4, TOS v2.06 in my Mega STe,
and TOS v3.06 in my STacy.

[DigitalSkunk]

Quite the collection you have there! How did you manage to get a hold of a STacy?

I always loved the aesthetic of the ST line, especially the Megas.

I want to start doing homebrew on my 520 ST once I graduate. Thinking Petari's TOS 1.04 Improved + the TOS 2.06 GUI will be the perfect combo.

Plus I can switch easily to stock 1.04 and 2.06 to test compatibility while having all of Petari's quality of life improvement on my older ST, and HD drivers right in ROM.

Also there a Blitter in there now... curious if I can find clever ways to leverage it for games.

 

[Ronald J. Hall]

Quite the collection you have there! How did you manage to get a hold of a STacy?

I always loved the aesthetic of the ST line, especially the Megas.

I want to start doing homebrew on my 520 ST once I graduate. Thinking Petari's TOS 1.04 Improved + the TOS 2.06 GUI will be the perfect combo.

Plus I can switch easily to stock 1.04 and 2.06 to test compatibility while having all of Petari's quality of life improvement on my older ST, and HD drivers right in ROM.

Also there a Blitter in there now... curious if I can find clever ways to leverage it for games.

 <img src="https://forum.8bitchip.info/Smileys/default/cool.gif" alt="" title="Cool" class="smiley">

I got lucky on the STacy. A guy I know that lived a couple of hours away had one that he was working on (he actually had more than one) and let me have it for $400.00. He even let me make payments on it. The catch is, when I got it and opened the box, it was in pieces. He didn't take the time to put it back together. So, never having taken a STacy apart, I had to figure out how everything went back together. That was entertaining. (this was probably 15 years ago or more). Of course, I've done crazy things to it now, including a Pak 68/3 board running at 40mhz, the RGB2HDMI mod for a color screen and more.

That dual combination of TOS should work well for you and your efforts.

I wish more games had taken advantage of the blitter. I mean, it's been around since the Mega ST's came out but a lot of software ignores it. It seemed like it wasn't really taken seriously until the STe came out.

[DigitalSkunk]

It really is a shame more software didn't use it. I think maybe I saw a forum somewhere about someone doing adaptations of games to make use of it, since it is such a wasted opportunity. Or maybe mentioning starting a project around that.

I get that a lot of thew time commercial software is made for "the lowest common denominator" but... you could even put a Blitter in most the earlier models with a manageable amount of effort. In fact, I feel like the ST was made for modding and upgrading. lol

Would be interesting to explore how manageable a task that would be. Would imagine that would be getting pretty deep in assembly, etc though....

Also that is amazing on the STacey!  Sounds like it was fun to assemble also haha (I really enjoy that sort of thing)

[Ronald J. Hall]

It really is a shame more software didn't use it. I think maybe I saw a forum somewhere about someone doing adaptations of games to make use of it, since it is such a wasted opportunity. Or maybe mentioning starting a project around that.

I get that a lot of thew time commercial software is made for "the lowest common denominator" but... you could even put a Blitter in most the earlier models with a manageable amount of effort. In fact, I feel like the ST was made for modding and upgrading. lol

Would be interesting to explore how manageable a task that would be. Would imagine that would be getting pretty deep in assembly, etc though....

Also that is amazing on the STacy!  Sounds like it was fun to assemble also haha (I really enjoy that sort of thing)

I've had so much fun with my STacy. It's currently apart, where I've been doing a bunch of upgrades. I'm wanting to get it right before I put it back together (they are notoriously fun to take apart).

I've got a few short Youtube videos where you can see some of the things I'm doing with it, and it in action.

Some great Spectrum pictures:
https://www.youtube.com/watch?v=cbHhlOskuc8

Music to drive off the Monday blues:
https://www.youtube.com/watch?v=I1JI0sADi1A

STDOOM at 40mhz:
https://www.youtube.com/watch?v=RcOMiAHXenM