TOS 2.06 in ST, Mega ST without 32 pin sockets

[ParanoidLittleMan]

I was thinking after this thread: https://atariage.com/forums/topic/296830-bought-wrong-size-tos-chip/

It is possible to solve TOS 2.06 in ST, Mega ST with existing 28 pin sockets if using EPROMs 27C512 . Will need 4 of them to get needed 256 KB capacity.

Chips may go direct in sockets on mainboard, except pins 20 of 2 EPROMs in middle (FD-H and FD-L). Will need special soldering pad setting and simple additional circuit for new address space - 1 GAL chip for instance. EPROMs 27C512 are still available.

[+DarkLord]

I would love to get TOS v2.06 into my Mega ST without

using a board that interferes with my AdSpeed accelerator.

 

[ParanoidLittleMan]

I made it in my Mega ST. Here is how looks:

EPROMs go in original sockets, so not higher. I soldered GAL on top of 1 20 pin TTL chip - that's where flat cable from CPU goes.

But it can be placed anywhere (near) . Need to solder some 15 lines, most is between CPU and GAL . That's only way without some intermediate board, sockets.

I'm ready to ship this - 4 programmed EPROMs (US 2.06 TOS is what I used here) + programmed GAL for decoding new address space of 2.06 for ST, Mega ST.

 

[+DarkLord]

Do you have any idea whether or not it will clash with existing accelerator

boards like the AdSpeed?

 

Thanks.

 

[ParanoidLittleMan]

According to what I read about AdSpeed it is 16 MHz CPU with some cache, so basically very similar to what is in Mega STE .

What means that should work with any TOS version.  Couldn't find some photo of installed ST version, so can not say how will be good to connect to CPU lines (mostly address) with GAL for address decoding. In any case, those lines - A17-A23, /AS, /RW, /DTACK are accessible at other locations too.

[+DarkLord]

Just to give an example, it won't work with the the MonSTer board - some kind of conflict.

 

[ParanoidLittleMan]

15 hours ago, DarkLord said:

Just to give an example, it won't work with the the MonSTer board - some kind of conflict.

 

That's pretty bad formulation. Since MonsTer self has TOS 2.06 support, you don't need this solution described here.

[+DarkLord]

Umm, that's why I'm *not* using the MonSTer board...and

thus, no TOS v2.06, because it conflicts with the AdSpeed.

[ParanoidLittleMan]

Not sure that it really conflicts. Someone has concrete experience and explanation ? Even IDE port on Monster should work well, because AdSpeed slows down to 8 MHz when accessing regular memory, ROM and bus (and IDE port is on it).

Of course, there may be conflict about how to install it physically.

[+DarkLord]

I had actually already bought one before I found out about it. In was in a thread on Atari Forum, I believe.

 

Alan H. explained that both devices use the same resources (IRQ line or address maybe?) I don't remember exactly

but I could probably look it up.