overclocking

Overclocking potential is variable from chip to chip. For example, my stock G3/300 processor went to 333/66 without a problem. It wouldn't boot at faster speeds. My G4 upgrade, rated at 350, overclocked to 466/66 and runs great. The stock G3/400 in my B&W wouldn't overclock at all. So as they say on TV, your mileage may vary. All you can do is try.

BTW, I tried changing the bus speed as well, but didn't measure any improvement and went back to 66Mhz.

Different chips in the the batch rate differently, some just make their rated speed others have room to clear and will go a good deal higher. Usually you will get at least one step higher as Moto liked to leave itself a bit of a margin I think.

I have a Blue&White 400 CPU in the beige running at 433, I could probably go higher but with my luck I figured thats enough lol. It does what I need it to.

Some people have problems with over clocking the bus speed as it messes up the PCI timing. Sometimes you can get away with it but some cards will not like it. Most people say there is no really improvement but upping it and it just adds the potential for trouble.

Make sure your heat sink is in good contact with the processor (And make sure the clip is on the right way around) to get rid of the heat.

--Spire

William,

Here below some links that may help to overclock your G3.

Some information about OverClocking a G3 processor
Other information from Takashi Imai Web Page. Jumper setting and related speed (bus and CPU)

If you are looking for user's experince follow this link

Hope this help

Mauro

One of the most troubling problems when you overclock is that any problems you experience may be blamed on overclocking. I like to qualify an overclocked beige G3 by asking it to run SETI at Home for a few days. The software is designed to compute at full speed, and write a disk checkpoint about every two minutes. If it fails to run all night and into the next day, it is not reliable enough for daily use. Time to back off one notch and call it done.

Overclocking the Bus depends on the speed of the "Grackle" memory controller. Some overclock happily, others not at all. It is also wise to have PC100-rated memory if you intend to bump the memory speed up above the stock PC66 it came with. The memory of the Blue & White G3 is PC100, and identical to the beige G3 memory in every other way.

Integrated circuit making still has a certain amount of "Black Magic" in it. In companies that build military-qualified products containing ICs, every chip must have a "second source" -- another Vendor who can make that same exact part, even if in pitifully small quantities, because chip makers have been known to "lose their Process" and cannot make any good chips for days or weeks before they blunder onto the right combination of steps that make their chip manufacturing process work again.

When they make those chips, there are dozens of them on a single wafer of silicon. They try to make them all identical, but the sizes of features are so small that it just does not work that way. Before the wafer is cut apart, the individual microprocessors are tested to see which ones work. Many are marked as bad at that point and are never mounted in an IC package.

Those that are packaged are tested to see how fast they can run without failing. Quite a few are trashed as too slow or defective at that point. The survivors are rated by what speed group they should be in, based on what speed they can run without error, and the speed group is screened on the top of the chip.

Early in the life-cycle of chip development, the slower ones may be plentiful, and the faster ones are few and far between. All the speeds are made from the same piece of silicon -- they are sorted by speed after manufacture. As the chip design is improved, the average speed may go up, and the yields on the fastest chips may go up substantially. [We are seeing this in memories for these Macs. The process is yielding many parts that can run at PC133 speeds, and very, very few that will only go PC66.]

Some of those chips could run faster than the speed on the top. Some just made the cutoff. Each chip has its own personality, its own limits. Some will run very fast for a little while, then get too hot and die. Each one is different. If they all could go top speed when they were made, they would all be marked as top speed chips.

What you are working with when you overclock is just how conservative are the manufacturer's requirements, compared to your own. If you can control a few more variables and take a few more risks, maybe you can get it to go faster. Then again, maybe not.

will takeing the system bus from 66mhz to 70 mhz hurt the logic board any. Is there a improvement over 66mhz to 70mhz if you notest any increase of speed. I wonder if once i get the cpu upgrade from sonnet the bus will stay at 70 or be defaulted to the stock 66mhz. it should lift the 66mhz bottleneck alittle at higher speeds well in therory is will. i didnt know there was a 75mhz spped setting on the beige i know there was 66 to 70 to 83mhz but personaly i think 83 might be to fast and i dont want to kill my beige

If it runs and the CPU does not get too hot, it should be fine. The bus speed has some impact on the PM106 "Grackle" chip on the motherboard, and on the memory DIMMs.

Many overclockers have used a handy free utility called "Gauge Pro" to read out the approximate temperature of their CPU chip after overclocking. Too high can cause damage.

The Blue & White runs a later version of the Grackle, which is rated at 100 MHz. The Grackle on your board will get flaky before it gets damaged.

The memories will not be damaged, but if you run them faster than their rated speeds, you risk getting bad data and/or bad instructions and a crash.

I do got pc100 clk2 sdram that i am useing so the memory wont be a problem. I will prolly just use the 70mhz or 75mhz if there is one to get a better speed then useing the 66mhz speed i hope it wont be to much of a strain in the chip its only going 4mhz-9mhz faster than the stock config

William,

my daughter's G3/333 MT runs exactly at 366Mhz, with the bus set at 75Mhz, according the the (usual) jumper chart. I could not make it any quicker (even playing around with the bus speed).
The system simply doesn't seem to be stable at speeds higher than 366.

cheers

Like Grant said, every chip will react different, and the only way to find out is to try a few different configurations.

I wasn't stable at all at 83MHz bus speed. So I backed down to my current setting of 315/70, and everything has been great.

I can't say I can notice the increase in buss clock, but overall, I've been very pleased with the overclock. I'm running 10.3 with no ill effects.

You definitely want to use Gauge Pro or I think Tattle Tech Lite has a temperature monitor, too. They only work in OS 9.

Rising temperatures is the first indication you might encounter problems. The computer will usually lock up or crash before CPU damage. But you want to monitor it.

Mine stays around 86º to 96º F. I think anything around a 100ºF is okay. Some run theirs hotter than that.

huh my system runs at the stock config 267.3mhz 66.8mhz bus speed as guage pro say's and it runs around 42C/107F. and when i do stuff it gets up to around 135F-140F and that is at stock config. and that seems like its allitle hot for stock. unless i have one of those chips that have no headroom. it does lock up some times i wonder if its because of heat it has the stock cooling and its a G3 266mhz cpu