exxos's Atari, Amiga & retro forum

PhilC wrote: ↑Mon Nov 02, 2020 8:30 pm I swapped out the -38 mmu and glue for the originals and the machine booted up just fine. So it appears there are differences between the old and current version. No idea what yet though.

Now we go into rumor territory ... but I _think_ I've seen it claimed that the very first MMUs couldn't do more than 1MB. While not obviously relevant (and might not be true) it's at least something that could be connected to memory addressing.

I have seen that happen where they would not recognise more than 1 MB.. But I have also seen where they do... But we are going back like 20 years here now... I could not really say if those chips were simply faulty because there wasn't a large enough sample set to reliably draw a conclusion.. And I would not have been very familiar with chip number variations back then either.

I guess anyone who has these older -20 chips which are not the "standard -38 numbers" could try them in a H4 / H5 to see if they really do see 4MB or not.

@exxos @troed I'll try a 4mb upgrade in the ST when I get time and will report back. It does have a mad9 line so hopefully just connecting that will work.