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From: [e-mail] (Guy Kuo)
Newsgroups: comp.sys.mac.hardware
Subject: Quadra Clock Modification - Long
Summary: Quadra 700 Clock Acceleration Instructions
Keywords: Quadra,clock,acceleration,oscillator
Message-ID: <[e-mail]>
Date: 22 Apr 93 04:33:57 GMT
Article-I.D.: shelley.1r577lINNjks
Organization: University of Washington
Lines: 149
NNTP-Posting-Host: carson.u.washington.edu

Here is how I modified my Quadra 700 for higher speed. Previously I
had been using a Variable Speed Overdrive for accelerating my CPU
but this modification is testing out as more stable at higher speeds.

Your mileage may vary. The top speed you achieve cannot be predicted
before hand. My personal Q700 has tested fine up to 32 mhz thus far.
I didn't have higher speed clock oscillators on hand to test higher
speeds.

Parts

	Clock Oscillators (4 pin TTL variety) You will need a selection of
	speeds beginning at 50 mhz on up. The CPU will run at 1/2 the
	oscillator speed. The original one is a 50 mhz unit. I recommend
	getting a 50 mhz clock in case you damage the existing one.

	   I obtained my clock oscillators from DigiKey 1-800-344-4539 for
	   less than $5.00 each. Some of their part numbers are:

		   50 mhz TTL Clock Oscillator (part # X121)
		   62 mhz TTL Clock Oscillator (part # X136)
		   66 mhz TTL Clock Oscillator (part # CTX137)

	   Don't get the half size clock oscillators. They won't fit.

	   There are also CMOS clock oscillators. I haven't tried one in a
	   Quadra. (They work fine in IIsi's)
	   
	Socket: Obtain a 4 pin socket which is in the same form factor as
	   a 14 pin DIP package. Alternatively, use 4 machined socket pins
	   from an Augat style socket. Just cut them out of the socket.

	Cooling Fan: A very small 12 volt fan to keep the CPU cool is a 
	   must. My VSO came with a specially modified heatsink which had
	   a fan built onto it. It had a pass-through connector which
	   tapped into the hard drive power cable. You should rig up 
	   something similar or risk frying your CPU.
	   
Procedure

1)  Insert usual disclaimer and antistatic warnings here.

2)  Remove the top lid of the machine. You will see the floppy disk and
    hard drive mounted in a plastic tower. Follow the usual anti-static
    precautions and of course make sure the machine is OFF when you do
    this. Unplug ALL cables, wall and monitor power supply cords from
	the back of the mac.
 
3)  Remove the power supply by pulling the plastic interlocking tab on the
    tower forward and simultaneously pulling the power supply straight up.
    The tab is a piece of plastic from the left posterior aspect of the
    tower which extends downward to hook on to the power supply. You may
    also feel a horseshoe shaped piece at the right portion of the power
    supply. Leave that alone. The plastic tab from the tower is all you
    need release.
 
4)  Look at the rear of the tower assembly. You will see the flat ribbon
    SCSI connector to the hard drive, a power cable and a flat ribbon cable
    leading to the floppy drive. Disconnect all these from the motherboard.
    The hard drive power cable connector has a tab which must be squeezed
    to release it.
                                            
5)  Unplug the drive activity LED from its clear plastic mount

6)  Look down the posterior, cylindrical section of the plastic tower. A
    phillips head screw is at the base. Remove it, taking care not to drop
    it into the case. A bit of gummy glue on your screwdriver is helpful
    here.

7)  Remove the tower assembly by pulling medially the plastic tab on the
    right side of the tower. This tab prevents the tower from sliding
	posteriorly. Slide the entire tower assembly 1 cm posteriorly then
	lift the tower assembly straight up and out of the case.

8)  Remove the interrupt switch assembly. It is a strangely shaped plastic
    device at the left, front edge of the motherboard. Pull the middle,
	rear plastic prong up and forward. The entire device will release.
	
9)  Unplug the speaker cable. Squeeze the plastic tab on the speaker to
    free it then swing it backwards to free it from the case.
	
10) Remove the motherboard form the case. Lift the front right corner of
    the motherboard about 1 mm. This allows it to clear the clear plastic
	Power light guide. Slide the motherboard forward about 1 cm. The
	motherboard then comes directly out.
	
11) Locate the 50 mhz clock crystal. It is a small metal box near the
    CPU chip. Note and remember its orientation. The new clock oscillators
	must be aligned with pin 1 in the same orientation.
	
	Very carefully desolder and remove the old clock oscillator. Some of
	the pins may be bent over. Simply desolder then unbend them. Be sure
	your desoldering iron is hot enough before heating the board.
	
	I used a suction desoldering iron to accomplish this task. This is
	NOT appropriate for a first soldering experience. The motherboard is
	a multi-layer design with very fine traces - easily damaged without
	proper care.
	
12) Install your socket or socket pins where the old oscillator once was.

13) Put a 50 mhz clock oscillator into the new socket. You could use the
	old clock but it has solder on its pins. This may come of inside the
	socket and cause corrosion problems later. I suggest using a new
	50 mhz clock.
	
14) Install your cooling fan system to complete the modification.
	
14) Reinsert the motherboard and slide it into place.

15) Snap in the interrupt switch assembly and speaker to lock the mother
    board firmly. Plug the speaker wire back into the motherboard.
	
16) Reinstall the tower assembly by first placing the right wall of the
    tower against the right wall of the case with the tower assembly about
	1 cm posterior of its intended position. Lower the tower assembly into
	place while maintaining contact with the right wall of the case.
    Once fully down, slide the tower assembly anteriorly until it clicks
    into place.
	
17) Reconnect the motherboard ends of the cables. DONT'T FORGET THE FLOPPY
    DRIVE CABLE.

18) Replace the phillips head screw

19) Drop the power supply straight down into place until it clicks in.

20) Plug the hard drive activity light back into its clear plastic mount.

21) Reattach your cables and power cords. Cross your fingers and turn 
    on the Mac. It should make the usual power on chord. If it doesn't,
	something is amiss. Immediately turn of the power and recheck your
	handiwork. If all is not well, you have my sincere condolences.
	
	Hopefully, all will work normally. Turn the machine back off and
	replace the 50 mhz clock oscillator with a faster one. Reboot and
	be astounded. 
	
	You will need to fully test the machine for many hours before deciding
	a particular speed is truly usable. With my VSO, a machine lock-up
	might take 8 hours of operation to occur. In the brief time since
	modifying my clock oscillator (36 hours) I have not had a single
	problem.
	
Good Luck to all who attempt this modification. There is a small but real
risk, but you could well reach Quadra 950 speeds or higher with less than
$50 in parts.

Guy Kuo <[e-mail]>