The Daystar Turbo 601/66 for the IIci can be modified to run at 90MHz for approximately a 20% performance improvement in CPU related functions. Unlike other clock-chipping techniques this modification does not increase the bus speed of the Daystar Turbo 601 card. Instead, it uses the fact that all PowerPC 601 CPU's have the ability to clock double and clock triple depending on how they are configured. These instructions tell how to modify your Daystar Turbo 601/66 card so that the PowerPC 601 will triple the clock signal instead of doubling it.
The Daystar Turbo 601 uses a 33.3333MHz oscillator. The PowerPC on the Daystar Turbo 601/66 version doubles it to 66.6666MHz while the Daystar Turbo 601/100 version triples the signal to 99.9999MHz. The circuit boards and most components are identical on both cards. To convert a 66 to a 100 nine surface mount (SMT) resistors must be removed, eleven SMT resistors added, and a 44 pin integrated circuit must be added.
I found that the modified card would work for only a few minutes before over-heating. It was thus necessary to replace the 33.3333MHz clock signal with a 30MHz one. This drops the PowerPC down to 90 MHz and allows it to operate properly.
If it isn't available there for some reason, ICS's headquarters number is (800) 220-3366 or (610) 630-5399. They should be able to tell you who your local distributor is. Their distribution system is heavily oriented by geography and the distributors won't sell to people outside their area. Wyle has some kind of arrangement that allows anyone in the US to order from them. If you are outside the US, e-mail me and I'll send you the contact info for your nearest distributor. The lists of distributors and sales offices takes up about four pages in their data book, otherwise I'd just publish it all here.
Solder is available at Radio Shack and at hardware stores.
Heat sink compound is available in small blue and white tubes at Radio shack for about $2.
Grounded soldering pencils are about $8 each at Radio Shack. They have a blue handle and (more importantly) a three pronged plug.
Remember to take anti-static precautions.
Remove resistors R5, R10, R11, R12, R22, R24, R28, R48 and R65. They can be hard to find. There will be some scanned in pictures of the board here that show their approximate positions in a week or so.
Be patient and don't force the resistors off the board. They will come loose when they are hot enough. Also, for something so small, they can store a lot of heat, so be careful not to burn yourself after you've removed them.
Now is probably a good time to take a little break.
This technique takes a little practice. I found that applying the soldering pencil to one side of the resistor almost simultaneously with touching it with the blade worked best for me. If I pressed the resistor with the blade flat, without softening the solder on either side, the resistors had a tendency to pop out of place. Be patient, work slowly, and don't be afraid to remove the resistor and start over. Be Gentle.
Place the resistors that you removed in step (1) in positions R6, R8, R13, R18, R21, R23, R27, R44 and R54. Place the additional 000 resistor that you obtained in position R60.
Since these are 0 ohm resistors, you should measure 0 resistance across the pads at these ten positions after the resistors are installed.
Place the 111 resistor that you obtained in position R25.
After you have installed all the other components the resistance across position R25 should be about 34.1 ohms. Up until I installed the last couple of resistors (R54 or R60) the resistance across R25 with the 111 installed was about 110 ohms. I installed the 9178 first, so I don't know if the resistance across R25 will be 110 or 34.1 without the 9178.
You may wish to use a continuity tester to ensure that all of your connections are good. I didn't find any problems when I did this part. It's really pretty easy, though you may have sore shoulders when you finish.
First you must remove the large heat sink from the PowerPC 601. From the back of the card, pop the four silver colored clips through their holes toward the front of the card. The heat sink will now be loose. Carefully lift it up, pivoting it around the black metal pin that sticks through a hole in the card at the far end of the card from the PPC chip. When it is at about 70 degrees to the card, you can pull the pin out of the hole. Set the heat sink aside. Do not touch the white square in the middle of the heat sink or on the PPC chip. That white substance is heat sink grease and is best not disturbed.
Next practice positioning the ICS 9178-02 chip on position U14. You want to get each pin on its own little solder pad. It takes a little work pushing it around to get all four rows of pins positioned properly. I used the tip of an X-ACTO knife to gently push it around. Some of the plastic TV tuner tools that can be bought as a set at Radio Shack might be a better choice for this task. The chip should be oriented as shown in the graphic. (as above, pictures will follow in a while) That is, pin one, the cut off corner, is in the upper left corner. The writing on the chip is oriented the same as on the PPC chip.
Then, when you are comfortable getting the chip positioned, remove it and put a tiny dab of the silicone sealant in the exact center of position U14. Don't get any on the pads. Then gently place the 9178 on the dab of silicone as close to properly positioned as you can manage. You want to use enough silicone to stick to the chip, but not so much that it squishes out onto the pads, when you place the chip.
Push the chip around until you have all the pins properly positioned again. The silicone is very viscous and should keep the chip from skittering around so much. Gently press the chip down, and solder one pin on each corner. The pads already have solder on them, so it should be enough to press the pin down onto the pad with a hot soldering pencil.
Once you have one pin on each corner soldered, make sure that the chip is firmly pressed against the board, so that all the pins are touching their pads. Now take a deep breath, let it out slowly and admire your work for a few moments.
Next you need to solder the other 40 pins. Work around the chip, soldering one or two pins on a side and then moving to the next side of the chip. This will prevent heating any one area too much. Be cautious, but don't worry too much. The ICS data book says the 9178-02 can tolerate 260 degrees C for ten seconds.
To solder the pins, carefully press each one onto its pad with a hot soldering pencil and hold it there for a moment or two until the solder on the pad has enveloped the pin. Be careful not to touch two pins with the pencil simultaneously. You need a pretty fine tip for this. I found that the stock tip on my new soldering pencil was thin enough. The tip on my older pencil was too fat though. I occasionally slipped and did touch two pins, but it never created a short circuit. Be careful, but don't get neurotic.
When you are done soldering, after letting the chip cool, it may provide some peace of mind to test your job with a continuity tester. I touched the end of each pad without touching the pin with one lead, and touched the other lead to the base of the pin against the chip. You should have a good connection for every pin.
Next, I went around the chip touching adjoining pins looking for shorts. Place one lead on one pad or pin, and the other on an adjoining pin or pad. Pins 20 through 23 are common, so no you don't have a short there, or if you do, it doesn't matter. Pin one is the top pin on the left side of the chip. The pins are counted counter-clockwise from there.
At this point your Turbo 601 is tripling it's 33.3333 clock signal and running the PowerPC chip at 100MHz. My machine booted in this configuration, and froze up after about 2 minutes.
This was the point where I attached the CPU fan to the heat sink. On the IIci, there is just enough room at the end of the heat sink to fit the CPU fan, so that it doesn't bump into the IIci's power supply when the card is installed. Adding the fan didn't really make any difference at 100MHz so you may want to skip this step at this point.
Now test the turbo 601 again. At this point my Turbo 601 not only booted, but also ran reliably. The CPU fan was still attached to the heat sink, because that adhesive usually only sticks once, and I didn't want to remove it if there was a possibility that I would need it later. So I haven't tested the Turbo 601/66 at 90MHz without a fan on the heat sink.
TattleTech 2.52 reports that I have a PowerPC Macintosh IIci and that my CPU speed is 90MHz.
I have tried clocking an unmodified Turbo 601/66 down with a 27MHz and 28.332MHz oscillator. It won't boot at 27. It will bong but not complete boot up at 28.332. The modified Turbo 601/66 might perform differently, but I doubt it.
If the Turbo 601 won't work with the 29MHz oscillator, then it probably isn't going to work. It will be a pain, but reverse your work. You will probably have to clip the pins on the 9178 and remove them one at a time. This is one reason why having a socket would be nice.
Before researching this modification, I tried straight clock chipping. The Turbo 601 doesn't tolerate altering its clock speed much. The first thing I tried was replacing the 33.3333MHz signal with a 40MHz one. That should yield 80MHz. The Turbo 601 will not even boot in this configuration.
At 38MHz, I got the start up bong once and then the machine froze. A 37MHz clock gave the same results as the 38.
The 36MHz bonged and then after a few seconds gave an error chime. I wish I knew more about music. I think it was four rising notes. The screen came on and stopped at the E-Machine's splash screen that my Futura IISX provides. The machine then sits that way without change. I didn't let it sit more than about a minute though.
The 35MHz bongs, and gets to the smiling mac icon. Then the screen momentarily does some narrow vertical bars and goes blank. Nothing more happens.
Next I tried clocking the Turbo 601/66 below 33.3333MHz just as an experiment and in anticipation of developing a clock tripling modification. At 30MHz the Turbo 601 works fine. However, CPU performance decreases about 40% where you'd expect about 10%. This decrease doesn't appear with the tripling modification in place, thank goodness, otherwise after performing the modification and running the PPC at 90MHz, you'd get an overall performance decrease of about 15%.
At 27MHz, the Turbo 601 won't boot at all. At 28.332MHz it performs much like it does at 37 and 38MHz.
All of the above were tried on the unmodified Turbo 601/66. The only clock speeds I have tried with the tripling modification in place, are 33.3333 and 30MHz.
The 31.3344 Clock: I don't know what the 31.3344 oscillator is for. I tried replacing it and it didn't appear to affect the board at all. I even disabled it completely and the board still worked correctly.
It's now been at 96MHz with a 32MHz oscillator for a while and it's been fine.
Booting up goes noticeably faster with the modified card. Launching applications and many Finder functions are quite a bit zippier. Some games are much faster. Marathon in high resolution isn't any faster. In low resolution it is faster. Apparently my video system is maxed out in high-res mode.
I am using a IIci, 32 MB RAM, a 2 GB IBM hard drive, E-Machines Futura IISX video card, 17" monitor, and System 7.5.1 with a minimum of extraneous extensions. I use Speed Doubler but not RAM Doubler.