Upgrading TOS 1.0 ?

[Mariano DM]

I'm having better results with my ST, able to run a couple of monochrome games and boot more or less consistentely.

 

I think most of my issues come from my TOS version. too old for most applications (especially image loaders). I was thinking about using Seltos or Ramtos to update to 1.04 without switching ROMS.

 

If I do the full upgrade, I think it would be better go all the way to 2.06. Having concerns about compatibilty, though.

 

Cheers !

[tjlazer]

For best compatibility get TOS 1.04. Rainbow TOS. GEM is faster too. Fixes FAT12 bug too.

[ParanoidLittleMan]

TOS 2.06 in ST, Mega ST needs more than simple ROM chip replacement. Needs HW logic, what can be single chip, because 2.06 is on different address, and is longer.

That costs little, but needs some soldering, wires. And some intermediate sockets too - 32 pin EPROMs needed for 2.06.

Compatibility problems - yes, especially with games. TOS in RAM may have compatibility problems too.

I have 2 chip original 1.04 - UK and De versions, but since your ST is from first revisions, pretty sure that there is no option to set it for 2 chip TOS ROM .

So, simple replacement needs 6 chip TOS 1.04 .

 

Btw., best is to have it all - switchable TOS v. Like 1.04, 2.06 ... and may have even 1.02 or 1.00 for some poorly coded games . Larger capacity EPROMs are not so expensive, and can have 4 or even more TOS versions in machine. All in 2 chips.

[JamesWD]

I have a TOS 1.02 (Mega Blitter version of TOS 1.0) just for playing some really old games that I have still have the original disks for. If I were to replace it TOS 1.04 would be the easiest.

 

As mentioned above TOS 2.06 would require some hacking the PCB.

 

Least pain is straight swap to 1.04 (check what ROMs you have inside first 2 or 6)

[Mariano DM]

You are right, it is a 6-chip version. Good to know before going eBay crazy

 

Ill keep researching before I decide for an upgrade.

 

Cheers

[Mariano DM]

Got my TOS upgrade, as it is 1.04 and 6-chip. hope there are no jumpers to solder.

 

Cheers !

 

[Forrest]

Let us know how the GBS 8200 works out. I'm thinking of buying one for my MegaST4.

[+Nezgar]

I take it those are just 6 x 27c256 EPROMs, drop-in replacements of the originals?

 

I guess you could make a 2 TOS switcher by using 27c512's and wiring the highest address pin (A15) on all 6 chips to a SPDT switch that toggles GND or +5V.

 

Is there a single solder point on the motherboard that could be used to inject a signal to A15 on all 6 chips?

[ParanoidLittleMan]

7 hours ago, Nezgar said:

I take it those are just 6 x 27c256 EPROMs, drop-in replacements of the originals?

 

I guess you could make a 2 TOS switcher by using 27c512's and wiring the highest address pin (A15) on all 6 chips to a SPDT switch that toggles GND or +5V.

 

Is there a single solder point on the motherboard that could be used to inject a signal to A15 on all 6 chips?

That depends from motherboard revision. Older ones, before 1987 have no soldering pads for setting ROM type, then pins 1 go direct to +5V . If there is soldering pad A16 and near to it chip 74LS11 then just need to connect middle part of that pad to GND if want to use lower part of 27C512 (second TOS), + remove soldering at "256K" . Of course best is to put there switch, like this: http://atari.8bitchip.info/p/TOSsw1.png

[Mariano DM]

Hello Guys

Thanks for all your pointers, the TOS update worked like a charm. 1.04 fixed a couple of nasty problems with UltraSatan. and I only bent 1 chip pin in the process.

 

The GBS 8200 only supports vga 30khz. for 15khz you need to combine hsync+vsync and make a custom cable.

Still deciding if building it or getting a 15khz monitor will be better.