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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...

We have now reached the first major milestone! This: Now it might not look like much but this techstep now has none of the original programmed parts installed. The main micro and all 3 PAL's have been replaced verifying that all the dumps are good! Work can now properly start on stage 2 :)

I think both me and @Kai Robinson have considered the IIsi and IIci but they are 6 layer boards so require completely redrawing like @Bolle did with the SE/30 rather than just tracing. I'll defiantly be looking at them in the future though if someone doesn't beat me to it My next board (after...

Just had the V1.1 IIcx booting for the first time last night :) Needs a couple of small patches but the design is 99% done

That's exactly what my breakout board dose :) (Well would do, if more than 4MB worked in the onboard bank) My intention is to replace the onboard bank with another SIMM or additional RAM on another module and completely ignore the onboard bank

If you ever feel like patching the LCIII ROM to recognize more than 4Mb it's internal bank I would love to get the LCIII booting with 16MB in the internal bank :)

Provisional version of the new DC in board is done: This comprises of a lithium battery charger, battery protection IC and associated dual mosfet and two boost regulators (+5v and +9V) This board can in theory be fitted to a original techstep however the +5V regulator should be omitted in this...

I thought they where 27C16's not 64's, need to have a look at my SE/30 board now..... Either way it doesn't really matter as the 28C64 will work fine to replace either :)

That 4 slot riser is very intersting, i'm guessing that PAL is generating additional RAS signals for the extra simms Given the marking of that chip (CE16V8) i'm guessing it's a PALCE16V8, hopefully it isn't protected as it might be hard to extract the code from it if it is

Me and @jajan547 are currently working on creating a replica of the Apple Techstep This will be a functional and (mostly) electrical clone of the original but will not be a exact 1:1 copy as the design will be optimised where changes can be made to make the board easier or cheaper to assemble...

Are those sanded or have they been painted over? it might be worth trying a little IPA on them Edit: Looking at the pictures I would guess U8 is the only PAL on there, looking very closely at the picture @Kai Robinson posted I *Think* its marked as a TIBPAL16R4 so hopefully this is unprotected...

Yep ROM's are socketed If someone whats to have a go at modifying it that would be really cool, software is not my expertise.... I tried 0/8/16MB, 0MB gives death chimes anything else works but only 4MB is seen

And a couple of things I have discovered while playing around: The LCIII needs the onboard RAM bank to be present otherwise it produces chimes of death (even with SIMMS in either or both of the other slots) and secondly that onboard bank is limited to 4MB, if you install more it simply doesn't...

Board layout, gerbers and scans are now on GitHub: https://github.com/max234252/MacLCII_Reloaded As with my other designs these are provided under a non-commercial licence but if you are a repairer and want to offer transplant services (or have any other commercial use in mind) please contact me