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Very interesting, That seems a very good way to go and is more closer to what I was originally thinking about doing Those Simms are had to get over here but I can easily get hold of 4mx4 DRAM IC's so could just design a similar simm assuming there is enough space in the LC case

Almost, two 32MB's and one 16MB. the top slot only has one RAS line connected to it so will only work with single rank SIMMS which due to the ammount of address lines available is limited to 16MB (32's have two ranks of 16MB each on them)

And the breakout SIMM and triple riser have been sent off to JLCPCB While i'm waiting for them I'll probably draw up a "direct riser" design too

I think if we are going that route I would be tempted to have a slot cut on the board, if it was the right width you should be able to get the correct angle on the simms without having to cut them Also I got some new 32MB SIMMS today and can confirm for anyone having doubts that 68MB 100% works:

Probably! :) My liking of this approach is for a couple of reasons though, it's more flexible as what's on the end of the cable could be a breakout board as pictured above or it could just be a RAM card with all the RAM soldered on it (Which I like as angled 72pin sim slots are extreamly hard...

I was thinking, why stop at two simms when you can have three! The top slot replaces the onboard bank and would only support single rank simms (Dual rank ones will likely just show as half their capacity) Really this is just a development stop gap, It's the quickest design I could think of to...

Interesting, I hadn't thought of doing it that way...... I'll need to do some measuring to be sure weather or not that would fit I suspect the floppy and power connectors might get in the way of the backwards facing simm's but i'll need to double check that

Funnily enough that was pretty much my initial idea, but I don't know if the signal trace length would be a issue I'm taking the approach of making a breakout SIMM that has connectors that can be plugged into either a RAM card or a riser module as this allows for flexibility of exactly what is...

This is one of the approaches I'm looking in to, just as long as there is actually space somewhere in the LC III to stuff the other simm slot

Normally the LCIII is limited to 36MB of RAM - 4MB onboard and one 32MB SIMM The simms are limited to 32MB as there are only 11 address lines hooked up to the RAM SIMM socked so larger sticks won't work (The will typically show up as 16 or 32MB) However while creating a pin listing for the...

I have some memory related shenanigans going on with the LC III at the moment, if what I'm planning works it's going to be really cool :)

Yep :) applying something between about 7v and 20v on VPP just before VCC goes high will often bypass the lock bit on GAL's. The exact voltage and timings vary between chips In theory this can be done manually with something like a TL866 and a bench power supply (I believe @Bolle dose it this...

Oh and as a bit of a aside I noticed U47 on my board was a GAL16V8 and since I needed to desolder it for cleaning I figured I might as well throw it into my Galdurino and see if it was crackable, and it was! 9V on VPP got the chip to divulge it's contents Attached is the JED and Equation file...

Quite a few years ago I got my hands on a Quadra 840av for a very reasonable price (£20) I wasn't really looking for a Q840 and tried to avoid buying it, but no one else at the sale I got it from seemed interested in it and given it's very reasonable price I couldn't resist it in the end! That...

Turning this mess (back) into a PCB looks like fun...

More multicolour spaghetti!

Pinout is different between the 5380 and 53C80 so it's not a straight swap. I just ordered one though and might try and rats-nest it onto the repro IIcx board and see what happens

Very nice! The no video issue is likely just bad solder joints, usually on the analog to logicboard connector, yolk connector or flyback (or all of the above!) I wouldn't even bother inspecting the joints at this point, just suck all the solder off them and put fresh on. Only start more in...

All in good time, gotta finish that half finished LC III schematic first :) Which reminds me I still need to send you that scaled down IIcx trace layout.... I'll remember to do it one of these days!