Use 4164 RAMs in place of 4116 RAMs



The 4116's used in the early Apple IIs run very hot and are fairly 
unreliable. They require +5v, +12v, -5v and 0v for power. We can 
actually adapt a more common 4164 RAM so it will fit into a 4116 
socket. This RAM runs much cooler, requiring +5v and 0v only, and 
tends to be more reliable.



Let's have a look at the pinouts of the 2 types:
         ___  ____                  ___  ____
   -5v -|1  \_/ 16|- Gnd      N/C -|1  \_/ 16|- Gnd
   Din -|2      15|- /CAS     Din -|2      15|- /CAS
   /WE -|3   4  14|- Dout     /WE -|3   4  14|- Dout
  /RAS -|4   1  13|- A6      /RAS -|4   1  13|- A6
    A0 -|5   1  12|- A3        A0 -|5   6  12|- A3
    A2 -|6   6  11|- A4        A2 -|6   4  11|- A4
    A1 -|7      10|- A5        A1 -|7      10|- A5
  +12v -|8       9|- +5v      +5v -|8       9|- A7
         ---------                  ---------


OK, well the data pins are all in the correct places but we'll need 
to do something about the power supply pins which are needed for the 
4116 but not the 4164. Also, the 4164 has 4 times the capacity of the 
4116 so we'll need to address that too. This turns out to be really 
easy, the A7 pin of the 4164 is in the same place as +5v on a 4116, 
so we don't need to do anything here and A7 will be tied high. Pin 8 
of the 4164 (Vcc) will be connected to +12v unless we do something 
about it. We bend the pin so that it won't go into the socket and 
jumper it to +5v - the easiest way to do this is to connect it to 
pin 9 on the other side of the chip. The surplus length of the bent 
pin 8 can be snipped off. Finally, pin 1 of the 4164 should not be 
connected to anything but will be connected to -5v if placed in the 
socket for a 4116. We can simply snip off this pin and all is well. 
This procedure can also be followed to use a 41256 as a 4116. Also 
in the IIe 80 column/64k card, you can bend up or remove pin 1 of 
a 41256 to replace a 4164. I have one with 2 such chips inserted and 
it works fine. I also have a II+ with a chip such as described above 
and no problems. If you need to or simply want to try this, and are 
not sure, simply email and I'll walk you through it. 
Thank you for reading. 

This page has been formatted for People using Apple IIs accessing 
the internet.