Macintosh Centris 610

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Centris610.jpg
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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.

General Information

The Centris 610 was one of the first mid-range computers to include a 68040 processor and the first Mac to be housed in the now-familiar low-profile case. It was replaced in October 1993 with the Quadra 610, which had a 25 Mhz full 68040 processor, but was in all other ways the same. The Centris/Quadra 610 sold for $2,520.

CPU

20MHz clock speed and features built-in paged memory management unit (PMMU) and 8K memory cache.

Memory

4MB of RAM onboard, expandable to 68MB via two 72-pin SIMM slots.

Video

The Macintosh Centris 610, Centris 650, and Macintosh Quadra 800 computers come with 512 KB of VRAM and sockets for expanding the VRAM to a total of 1 MB. The VRAM in the Macintosh Centris 610 computer uses 100-ns devices.

Expansion

The Macintosh Centris 610 has a single expansion slot that accepts an adapter card for either a processor-direct slot (PDS) card or a NuBus card.

Modifications

Clock Mod

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

Troubleshooting/Repair

Capacitor replacement

The SMD capacitors on the logic board will most likely have already started leaking electrolyte out the bottom, and failing to replace them in a timely manner will result in further leakage with possible damage to nearby components. See below list of capacitors to replace:

  • 10 x 47uf 16V

Gallery

Documentation

See Also

The Macintosh Centris Series from Apple Computer
Macintosh Centris 610 -- Macintosh Centris 650 -- Macintosh Centris 660av