exxos's Atari, Amiga & retro forum

OK, seeing as I've decided to try to build this thing I thought a separate thread for the progress would be a good idea.

So, the primary aim of the project is to fit a TF536 into a 520STFM case and allow the top shield to be fitted normally.

In addition, it will have on-board a socket for an Exxos dual TOS ROM with a jumper to switch between the two ROMs, decode circuitry and jumpers to say whether the ROM image needs to be placed in the TOS 1.0{2,4} address range or the TOS 2.06 range. (I envisage that you'd use a jumper to set the ROM address range for each half of the ROM and then have trailing wires going to an external switch on the case.)

And yet more... use @derkom 's relocator design to also have the 68000 on the board so that you can switch between that and the TF536.

Having this all on one board makes things simpler for users as they "merely" have to replace the CPU with a socket, remove the ROMS, re-fit the CPU on the board along with a DualTOS ROM and they're away. They can then add the TF536 (or anything else) later.

From my initial investigation it looks feasible, at least space-wise.

(This next bit is for my own reference really)

With regards to the ROM decoding, due to the dual ROM switching I can't use exactly the decode system @DoG referenced, instead the address line decode can easily be done with a 16V8 GAL, outputting either one or another output high if one of the address ranges is being accessed, then a modified version of the circuitry DoG referenced can be used to do /CE and /DTACK.

For the old TOS, the line would be high if the top byte of the address is 11111101 or 11111110.
For TOS 2.x it's simpler as you just look for 111000xx, so you can ignore the bottom two lines.

stephen_usher wrote: 24 Sep 2020 10:55 And yet more... use @derkom 's relocator design to also have the 68000 on the board so that you can switch between that and the TF536.

You might want to ponder using a PLCC 68k for this, depending on how tight space gets. On my Stacy switcher, I had to use the DIP 68K because of needing to fit the other expansion boards, but a PLCC would have permitted a considerably more compact design.

I'll be going for the DIP package for two reasons:

(a) I was envisaging people reusing their original CPU.
(b) Not only do I have the original but I have three spare ones, including a spiffing ceramic and gold one. :)

stephen_usher wrote: 24 Sep 2020 12:24 (b) Not only do I have the original but I have three spare ones, including a spiffing ceramic and gold one. :)

Can't argue with that logic. :lol:

stephen_usher wrote: 24 Sep 2020 12:24 I have three spare ones, including a spiffing ceramic and gold one. :)

Don’t ever recall seeing a gold 68k. My google-fu didn’t show anything. Photos please!

chue wrote: 24 Sep 2020 15:31

stephen_usher wrote: 24 Sep 2020 12:24 I have three spare ones, including a spiffing ceramic and gold one. :)

Don’t ever recall seeing a gold 68k. My google-fu didn’t show anything. Photos please!

Here's a picture of one. It's merely the ceramic package.

I am envious! That is indeed, very "spiffing". :)

The TF536 from @PhilC arrived today, allowing me to look at a good location for it.

This seems to be the best place. There's definitely no room for ROMs in the normal location so bringing the ROM and decoder onto the relocator board is a must.

OK, not strictly the project, but I decided that my dev machine needed a bit of a sprucing up, so I gave the case a good clean and then a quick, light spray job. Before During After

OK, now the keyboard looks awful, but the retr-brightening of that will have to wait until next Spring now.

Anyway, on the project front, now I have the TF536 and been able to put the machine together again it's clear that there's no way to get the TF underneath the shield, the 68030 is just too tall. The board will have to go in the orientation shown in the previous posting otherwise the IDE header will interfere with the bottom of the keyboard.

@exxos What model eeprom do you use for your dualtos?