Macintosh Centris 610
The Centris 610 appears to be the slowest of the 040 based Macintosh systems as it uses a 20MHz Motorola 68LC040 processor. The case design is shared with the Macintosh Quadra 610, Macintosh Centris 660av, Macintosh Quadra 660av and Power Macintosh 6100.
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]>