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Maybe I'm going mad, but the DS1307 has a completely different pinout to the apple RTC from what I can see.... The 512K and Plus seem to use pats with the same pinout: But the DS1307 is differen't: I stand corrected on the hole "should work in the II series" thing though, the 128k / 512k do...

I was under the impression that the 68000 compacts and mac II family used the same RTC hence my "should work" statement but it is entirely possible I am wrong there! Still waiting for the chips so Ic an do some experimentation

Oh sweet, I thought that was a custom chip! Ordered a few for testing :) Off the top of my head I belive that chip is used in the 128k -> SE/30, as well as the II, IIx and IIcx (as well as the classic however that has the chip in a different package)

The extra pins are for extra address signals to allow for larger ROM's to be used, this was presumably because apple had plans to release upgraded ROM's at some point but never did

Time for a little update: The logicboard has been stripped and scanned and I am currently working on tracing the outer layers This is only going to be a aide for generating a schematic though, the board is a 6 layer one so simply tracing it in sprint isn't going to be possible (And even if it...

Unfortunately that one is a no-go, looks like the design is not a universal as I was hoping it would be (Causes some eintertaining chimes of death when installed in a IIcx). Still have a couple of in the works variants of that card though (pending compatibility and if I can find a nice way in...

16 on each side :) (It just looks like there is nothing on the other side as the chips are sitting exactly on top or each other)

And while where here, here is a custom quad rank SIMM for the LCIII: 32 RAM IC's was quite a lot to squeeze ona 72pin simm! :) Just have to hope it's not going to be too tall to fit in the case now!

Yes probably, I only say "banks" as that is what is logical to me even though it is probably technically incorrect . From here on in we shall refer to them as "Ranks" :) Don't know why I keep not answering that - no I don't. I'm purley working on what About this Mac reports, I think the...

Ok, let me start over because I think we are getting crossed here The LCIII supports 5 "Banks" (Banks may not be the correct technical term but it is what makes sense to me) Each Bank has one unique RAS line Bank 0 is the onboard soldered RAM Banks 1 and 2 are the 72pin simm socket Banks 3...

Gotta love it when a new board design works on the first try :)

Just tested it, unfortunately the LC is still reporting only 4MB of ram with 16 installed

Great, many thanks! I'll test it after work tomorrow and report back

Awesome :) 16MB is what I am trying to replace it with (Anything higher than that requires more RAS lines then we have)

Not yet, It's been cleaned up and recapped and had some minor trace repair done but dose not chime when powered on, after not being a easy fix it's slipped back down my list of stuff to work on....

Sure, I'll post the KiCad project on here later tonight Not a full one, I got 3/4 of the way round the chip before getting distracted by the hole "ooh there's two extra RAS lines" rabbit hole :) Bank A (the onboard bank) is restricted in ROM, I have tested this by removing all the soldered...

Thanks @trag I was having the same problem as @alxlab "Where the hell is 2^27 coming from!" it makes sense to me now and I can get the maths to work :) I have done some more testing with the simm breakout board and am pretty confident that as it is it just isn't going to work, I have scoped...

So I have enever been able to wrap my head around the maths, but my understanding i is that you need 11 address lines to fully address a 16MB bank (x2 banks on the simm for 32MB) and you need 12 to fully address 64MB (x2 banks on the simm for 64MB). I could be totally wrong though so if anyone...

No idea.... I would need to dig through the LC475 devnotes and see how much free space is above the official RAM block in the memory map, IIRC the LCIII has just under 1GB free space above it's official RAM block so I would guess the 475 would be something similar, if that is the case one of...

FWIW I think the creators of most of these projects will sell small quantitys and possibly assembled / partially assembled / programmed ones if contacted (parts and time permitting) If anyone wants a assembled one of my SE ROM replacement boards please fell free to contact me, I have pleanty of...