A while ago I found a hack how to add 64MB or RAM into the Amiga 4000 motherboard:

To get there just check http://www.amibay.com/showthread.php?57613-64mb-fastram-to-your-A4000-mobo

ONE SIDENOTE: this hack will NOT work on Rev D Amiga 4000 (those with the 030 soldered onboard) or the A4000T

But this required cutting traces on the motherboard. so. how to do it WITHOUT cutting wires?  well some work but this is how I did it:

First of all you will need some files to program the GAL etc. and here is one place to download the files: 64MFiles

This DOES require alot of soldering. so the above link might be more EASY. but then you need to cut traces.

So first I had to remove the RAMSEY chip, I do that with my hot-air station.

so when I have removed the ramsey, I clean up the pads:

(shiny picture.. :))  nice and clean. also removed the solder on the U860 spot.

Now solder one wire from U890 pin 45 to U860 pin 14, and one wire from U89 pin 46 to U860 pin 13.

Also solder a longer wire to U860 pin 17. (this will be a wire to the back of the board to the SIMM sockets. put it trough a VIA hole or so. (the big hole you see is for the CPU card spacer.. not recomended to use).  also one of the hacks reuires cutting pins of the U860. but to be sure. just insulte the pins with a piece of kapton tape:

Now they will not be connected, no cutting needed so solder in a socket in U860 now (the wires shold be connected so take care), and now well as this hack requires cutting traces to the ramsey.  Actually to pin 45 and 46 that was used above.  so instead of cutting, insulate them with more Kaptontape:

Now they will not be connected to the RAMSEY chip.   Well now it is time for the pull-up resistors needed to “fool” the ramsey chip:  I decided to put them UNDER the ramseychip as I will put it in a socket.

so I just take a normal socket:

and remove the bottom-plastic plate. and locate pin 45 and 46, solder a small wire to it and solder a 4.7KOhm restistor to them:

I insulate them with a shrinktube.

Solder it to the socket: (remember to skip pin 45 and 46 as you insulated them with kaptontape)

and solder the 2 loose wires to pin 47.  let the resistors be even in the MIDDLE of the socket. so you can push down the Ramsey later.

Now. time to fix the wire to the SIMM socket. (you know the one you soldered to pin 17 of U860)

flip the board around. and you should have the wire through one of the via holes:

at the end of this wire solder a 33Ohm resistor:

and Insulate with shrinktube:

Now solder it to the first FASTMEM SIMM Socket pin 19, also solder wires connecting all fastmem sockets pin 19 to eachother:

and secure them. I always use Kaptontape:

Now you need to program a GAL 16V8 with one of the codes in the file above. this will work with V3 of the hack. V6 should work aswell, not sure.

Put in the GAL and ramsey in each socket:

Put in 4 16MB simms instead of 4MB simms (this is more or less the ONLY legal configuration now.  2 32MB simms should work in every other socket)

Boot up and:

64MB of fastmem on the Amiga 4000 motherboard.