Seems some of the CPU board designers didn't think about the thermal issues. When the CPU is put on the side that is agains the motherboard the heat has a hard time to escape.
It also confused me slightly 
Btw, how many layers is the A4000 motherboard?
That was only with the 30. With the 40 it was face up and you could fit a heat sink. Very convenient to add more cards to the board without interfering with the main daughter board for the other cards. I even have one card fitted to a 4000 that is just a fan. Never had any heat issues with a 4000. Amazing how much stuff you can get into an A4000D box. I have A4000s in towers also and that helps I guess.
Dunno what layers you are talking about really. If you mean the actual build up of the board I wouldn't know. In terms of the physical larger structure you have the main board, a perpendicular daughter board and the processor board. Remember with the more powerful boards they need the extra plastic supports. Many of these machines failed because of a poor connection between the board and the long connector slot. Even had that with my 4000T and the Cyberstorm PPC.
