Hardware and TOS questions about MEGA ST 2

[chad5200]

Got my old Atari MEGA ST 2 up and running. Opened it up and cleaned everything up. Cleaned the read/write head on Floppy Drive and so far everything seems to be working great!

 

Few questions...

 

1) My TOS ROMs (populating two of the six slots) are labeled C101629 and C101630. What version are these? Is there a newer TOS version that is recommended for the MEGA ST? I have an EPROM burner so I can easily burn new ROMs. Is there a link to the better version that I can download and burn myself?

 

 

2) It appears as if there are empty spaces where I can add more RAM. Possibly increasing my RAM from the existing 2MB to 4MB? If so, is this possible and are the steps detailed for this? I am very good at soldering so I have no problem performing this upgrade if possible.

 

 

3) Is there diagnostic software that I can run to fully test the system (RAM, etc)? If so, can you provide a download link?

 

 

[ParanoidLittleMan]

You can check your TOS version simply by clicking on Desk, Desktop Info . If year is 1989 it's 1.04, if 1987 it's 1.02 .

Or google for those labels. 1.04 is latest for ST machines.

In case of RAM hardest part is to get proper chips now. Or it may be solved by adding some 2 MB module .And later means less soldering.

I have 2 MB module good for. Have improved TOS versions too: http://atari.8bitchip.info/tosimav.html

But that's mostly for usage with newer mass storage like UltraSatan.

 

Sorry, but really can not go in some detailed guides here. I still working on improved TOS, right now too. And all it is online, in forums, just need to use little search for.

Just to add that you can use even TOS 2.06, but that needs some extra HW logic and extra sockets with 32 pins.

[chad5200]

The year on my Desktop Info is 1987 which means this is 1.02.

 

Is there a link to download the ROM files for 1.04?

 

Thanks!

[snarkdluG]

TOS images can be found at http://www.avtandil.narod.ru/tose.html for example. You have to split them though. Use http://atari.8bitchip.info/ROMSPLIT.ZIP

Edited May 29, 2019 by snarkdluG

[chad5200]

Thanks for the TOS images link.

 

Is there a version of the ROMSPLIT that runs on Windows PC?

 

Or is there a download that has these ROM files ready to go for an EPROM burner?

[ParanoidLittleMan]

Correct link: http://atari.8bitchip.info/ROMSPLIT.ZIP

There is no Windows version, and I will not do it for sure (I made Atari version). You have Atari emulators for Windows (Steem, Hatari), and can run there that Atari program - so under Windows in fact. All it needs really little time to DL and set up.

You will not find splitted TOS ROMs online. Most of it is used in emulators, so full TOS image files. Those with EPROM burners usually have, know what tools to use.

Btw. there is some hex editor or like for WIn, what can do hi-lo split, but why should I search for it instead thread starter ? Any problems with using google ?

[chad5200]

Thanks for the info.

 

I hoped that someone might have the ROM files ready to go in a .ZIP file for a modern EPROM burner in a .BIN, .HEX, or .ROM format. This would greatly simplify the process of burning a ROM on modern equipment.

 

I've downloaded many ROMs (for Atari 8 bit, for pinball machines, for arcade machines) and they are all ready to go for a ROM burner.

[ParanoidLittleMan]

Yeah, welcome to 16-bit World 8-bit ROM does not need splitting in low-high. Atari ST is 16 bit.

I had Sinclair Spectrum, and can say only that with Atari ST things are way more complicated. If nothing else, ROM is 20x longer.

Should start to install those emulators instead making adverts for even older retro stuff

[chad5200]

I have installed the Steem emulator as you suggested and was able to split the 1.04 TOS file into two (TOS104US.HI and TOS104US.LO) and should now be able to burn these on my EPROM burner. Thank you for your guidance!

[kodak80]

I have installed the Steem emulator as you suggested and was able to split the 1.04 TOS file into two (TOS104US.HI and TOS104US.LO) and should now be able to burn these on my EPROM burner. Thank you for your guidance!

You may find that the ePROMS for using 2 chip TOS is a bit more complicated than just burning them. 2 chip TOS is 28 pin and programmable chips in 28 pin format no longer exist. There are 2 options: 1. convert the Atari to 6 chip TOS ROMs (which do exist) or 2. use 32 pin chips and follow guidlines for using 32 pin ROMs in 28 pin socket. All of this information is available on the various Atari forums.

Edited May 29, 2019 by kodak80

[chad5200]

I will go the route of splitting TOS into six 27C256 EPROMs.

 

But now I think I have to figure out how to rearrange the jumpers for this to work. The scavenger hunt for this information continues.

[chad5200]

I've looked and I cannot find this info...

 

Can anyone tell me the arrangement for the jumpers for a six ROM configuration on the Mega ST?

[chad5200]

I found this information in the Schematic which can be found here:

https://archive.org/details/Atari_Mega_ST_Schematic_1986_Atari/page/n5

 

Here is the relavent part:

 

Is it safe to assume that for the six ROM option, I should be doing the first row (labeled 256K) ? It also mentions that U12 is "NO USE". Does this mean I have to do something with U12? Or is it's functionality just ignored in this configuration?

 

 

 

[chad5200]

I'm bummed.

 

I've split the ROM into six parts. I've burned them to six 27C256 EPROMs. I pulled out the original two ROMs and inserted the six EPROMs. I jumpered W4.

 

I moved W2 to 1-2 and W3 to 1-2. But it's not working. I got a white screen with 4 bombs.

 

I then thought maybe I need to do the third row (1M x 6) and moved W2 back to 2-3 and W3 back to 2-3. But still not working and now it's just a white screen with no bombs.

 

Any assistance would be much appreciated.

[chad5200]

SUCCESS!!!

 

Here is how it is supposed to be. Hoping this will help the next person.

 

If you want to have TOS 1.04 (Rainbow TOS) running on six 27C256 EPROMs in your Mega ST 2:

 

W2 must be jumpered. W3 must be jumpered at 1-2. W4 must be jumpered at 1-2. U12 (74LS11) must be removed or at the very least (which is what I did) cut the pin that gives it power... this is pin 14 (the pin on top far left).

 

That's it!

Edited May 30, 2019 by chad5200

[ParanoidLittleMan]

Sorry, but man must sleep during night. Good that you solved it self, but again sorry - U12 does not need to be removed, even if is not in use. There is some line, 0 resistor from it's output to remove. Cutting power of some IC is very bad idea, and will cause damage sooner or later. And it may even not work at all - depending on what is connected where on that IC - talking generally.

 

I looked my Mega ST, and it seems that it is little improved v. - there is R33 between U12 and W4 - so it is enough to remove only it in case of 6 ROM chips.

I suggest that you: 1. remove that chip completely if want to stay at 6 ROMs.

2. Better is to leave it in, with power connected, and cut line between pin 12 of U12 and W4 - or cut pin 12 self. Much easier to restore than putting back complete IC.

 

I blame here Atari little - they saved 1 0 Ohm resistor, made confusion with that 'use', 'not use' . Not thinking that after 32 years people still may replace TOS TOM chips What a short sightedness !

Btw. you can use 512K EPROMs too, and have 2 switchable TOS versions im machine: http://atari.8bitchip.info/tosimav.html

 

On pic with 6 EPROMs is visible placement of chips (if not printed or visible on motherboard).

 

And, I think that you should not come with some guide after so little experience with Atari and electronic, and not really good solution. But that's what people like. But good thing is - nobody will see this thread after week-two Did we learn something here ? Me yes - no progress by humankind. People want power (no wonder so many silly superpower movies), but what is really useful is not power, but being wise, and using that little power you have with brain, in good purpose. Too bad - it needs time and forgetting own little interests.

[Wally1]

We need patience, not power

 

from the Holy Bible

[chad5200]

Thank you for your insight.

 

I have reconnected pin 14 on U12 (74LS11) and disconnected pin 12 instead. I wish I could edit my post above to note this correction but it appears I cannot.

[Wally1]

If you have a paid member ship you can edit old posts.

[pluto63]

Not so useless topic anyway, reading the entire post solved my problem of converting my mega st4 to 6 x eprom. Socketed the 74ls11 ic and all perfect. Nice idea the 512 eprom switch, I,d like to experiment with tos 2.06 and Peter said something about a hardware patch needed, any info on this?

Edited October 3, 2020 by pluto63

[ParanoidLittleMan]

12 hours ago, pluto63 said:

Not so useless topic anyway, reading the entire post solved my problem of converting my mega st4 to 6 x eprom. Socketed the 74ls11 ic and all perfect. Nice idea the 512 eprom switch, I,d like to experiment with tos 2.06 and Peter said something about a hardware patch needed, any info on this?

It can be solved really simple and cheap. http://atari.8bitchip.info/flashest.php

On about 80% of page is schematic with txt: "No GAL programmer? There is a simple solution:"

That's for TOS at address $E00000, where 2.06 is. And actually, it can be even longer than 256 KB.

Instead ROMCE, if 74LS11 is not present may use ROM2 line ($FC0000-$FCFFFF) - it is needed only at start.

Possible with 1 GAL chip too - needs programmer for.