Newsgroups: comp.sys.mac.hardware
Subject: centris-clock-mod-11 (FAQ, long)
From:
[email protected] (Guy Kuo)
Date: 7 Jun 93 06:26:04 GMT
Organization: University of Washington
Keywords: centris,610,clock,oscillator,acceleration
Summary: Version 1.1 of FAQ/Instructions for speeding up Centris 610
Centris 610 Clock Mod Version 1.1
by Guy Kuo
This information is only for those who are technically adept. The process
requires soldering leads to surface mount components. This is not a good first
soldering project and should be done only with electrostatic discharge safe
equipment and the usual ESD workmats, etc. You will void your warranty. If you
ruin your motherboard, your friends will laugh at you.
Now that you have been properly warned, the procedure:
1) Apply ESD equipment and open the Mac. The power should be disconnected and
the machine properly grounded. Disconnect and remove the hard drive to gain
access to the clock oscillator. The metal shield in front of the hard drive
pops off. The hard drive then slides forward and out.
2) Look just in front of the CPU. You will see a small 4 pin plastic IC
which is marked 10 MHz. That is the original clock. You may either desolder
it and replace with a new clock of a higher speed or install a socket. I
prefer to place a socket.
3) Assuming you wish to add a socket, obtain a 14 pin IC socket. Remove all
pins except numbers 1, 3, 5, 7, 8, 10, 12 and 14. If you use a machined
pin socket simply push the unwanted pins out with a needle nose plier.
4) Cut the socket leads off the corner pins (#1, 7, 8 & 14) The remaining
four central leads will later attach to the original oscillator.
5) Use some hook up wire on the underside of the socket to connect
pin 5 to pin 7.
6) Connect pin 8 to pin 10.
7) Connect pin 12 to pin 14
8) Mount the socket such that pins of the socket match the oscillator pins
as below. This means the socket's four pins ride on top of the original
oscillator's leads. Simple lap joint soldering holds the socket in place.
Socket Oscillator
3 1
5 2
10 3
12 4
9) Install a wire jumper between socket holes 3 and 5. This grounds the output
enable pin 1 of the existing oscillator disabling it.
10) Install a full size TTL oscillator into your 14 pin socket. Pin 1 of the
new oscillator goes into pin 1 of the socket.
11) Add a heatsink and (optionally?) a cooling fan to the CPU. I routinely
add a cooling fan on top of my heatsinks for this type of modification.
A 40 mm low profile 12 volt fan will do nicely.
12) Turn on the machine and it should "Bong" as usual. If not, IMMEDIATELY
turn power off and recheck your connections.
If you do not understand how this procedure works, very seriously reconsider
whether YOU should be doing it.
To run the machine at normal speed, unplug your oscillator and remove the
jumper wire between socket holes 3 & 5.
Remember the numbering of the socket top view is:
14--12 10---8
----------------
| |
> |
| /--\ |
----------------
1 3 5----7
The on board oscillator pins are numbered:
4 3
------
| |
> |
| |
------
1 2
Clock chip speed is 1/2 the desired speed so order appropriately. Do not
obtain clock oscillators with output enable on pin 1 for this procedure.
If you insist on output enable oscillators, you must add a 1 k resistor
between socket pins 1 and 14 to enable your new oscillator.
Digikey at 1-800-DIGIKEY is a reasonable parts supplier. Here are some part
numbers:
ED3314 14 Pin Machined gold contact socket
HS154ND 0.25 inch tall heatsink for 68040 with clips
Some reasonable clock oscillators to obtain are:
CTX114 10 MHz
CTX131 12 MHz
CTX115 14.3 MHz
X127 14.7 MHz
Please send E-mail so I can gather and summarise successes and problems
with this modification. Good luck and enjoy your new super fast C610.
Guy Kuo <
[email protected]>
