exxos's Atari, Amiga & retro forum

Byteswapping issue ?

exxos wrote: 09 Apr 2020 19:49 Byteswapping issue ?

Anything is possible. As I say, when it comes to programming ROMs, I don't know what I'm doing. But the TOS 1.04 and 2.06 images look sufficiently similar in the programmer software that I would guess they are both in the correct format:


At 10€ a chip, and a very small supply of blanks, it's not something I want to stab at randomly. ;) Unless there's a simple explanation of something I've probably done wrong, perhaps I should build up that 27C4096 emulator. :)

You would need to look at the hex codes on the ROM that works... For example 104 in the second byte is 0401, or 0602 for tos206.. But you need to verify what your programmer comes back with on a working ROM..

As @exxos says, some roms need to be byte swapped for some programmers. For instance a rom that works fine in a TL866 needed to be byte swapped to work in my new programmer.

The way I usually work it out is by finding the text section in the rom file whilst browsing it with the programmers software. If its readable you are usually ok to burn it to a 27c4096 or similar, if not, you will need to byte swap it first tilliys readable.

It just occurred to me that I could pull the dual TOS chip out of my STE (with exxos' switcher installed), and sure enough, 2.06 boots fine off that chip.

So the problem is indeed something with the way I'm programming, not with the board. I will poke around at this more, hopefully without going through more than one more chip. :mrgreen:

what programmer are you using?

I can send you a 1.04 / 2.06 file that I use?

PhilC wrote: 09 Apr 2020 20:26 what programmer are you using?

TL866II PLUS

derkom wrote: 09 Apr 2020 20:27

PhilC wrote: 09 Apr 2020 20:26 what programmer are you using?

TL866II PLUS

ok, gimme 5, I will post a rom file that works for me.

PhilC wrote: 09 Apr 2020 20:12 The way I usually work it out is by finding the text section in the rom file whilst browsing it with the programmers software. If its readable you are usually ok to burn it to a 27c4096 or similar, if not, you will need to byte swap it first tilliys readable.

Yeah, this was the key to me realising it's byteswapped. I found some text and it's all out of order. Makes sense I guess, 68k being big endian and I'm writing the ROM on a little endian system.

PhilC wrote: 09 Apr 2020 20:28 ok, gimme 5, I will post a rom file that works for me.

You don't actually need to. I can byteswap the image I've got, although I suspect you'll get it posted before I tell you don't need to. ;)

LOL, had just pressed the reply button to say I can't send it as my win doze laptop has finally died (fan failure).

Glad you got it sorted.