Beige G3 Jumper Settings

Caution: Use at you OWN risk

This page contains information on setting the system speed jumper block on a BEIGE G3 motherboard. Parts of this information may apply to the BLUE & WHITE motherboard, or the G4 PCI GRAPHICS motherboard, but has not been verified.

If you set your clock speed to high your CPU will run unreliably. Sometimes it won't start at all, other times it will crash at start up or run for periods of time and then crash. You can cause damage to your processor or your motherboard easily by misusing this information. I take NO responsibility for any damage either direct or consequential you do by using this information. Use at your own risk. Whatever you do, please be careful.

The process of setting your Beige G3 motherboard and processor speed:

1) Set a speed for the PCI slots bus portion of your system's bus.

2) Choose one of two allowable values to muliply the PCI speed setting by, which will set the SYSTEM bus speed. Note that many people believe that what you are setting is the System bus, and the multiplier is used negatively to set a lower PCI bus speed, but no apple engineer or person in the know has ever been able to confirm that for me. As is said: "six of one, a half-dozen of the other...".

The majority of G3 ZIF based processor modules understand up to the 8x multiple value, many also understand the 8.5 and 9.0x multiple values, and a small amount also allow up to 9.5x and 10x multiples. Note when purchasing a ZIF (be it G3 or G4 equipped) the highest multiple supported.


The Beige G3 Jumper block:

STEP 1 - Set the PCI Bus speed in megahertz. The stock setting is 33.3, and the lower and higher settings should only be used when you are sure you have PCI cards that are compatible. Be aware that not every motherboard functions optimally at every setting. I personally have had no problems with various Ethernet, SCSI, and Graphics cards in Beige G3s at the 35.0 PCI bus setting. Differences in components, motherboard revisions, and other factors lead to different performance and reliability out of motherboards from the same family.

Pair Num. . PCI Speed
7 8 9 .
S S - . 30.0
S - - . 33.3
- S S . 35.0

STEP 2 - Set the value to use to multiply the PCI bus speed by. This value will be used to multiply the PCI bus speed, and will set the SYSTEM bus speed. There are two allowable settings and values, 2.0 (short pairs 5 and 6) and 2.5 (shor pair 6 only). The value for shorting pair 5 only is apparently undocumented and should NOT be used.

Pair Num. . PCI Multiplier
5 6 .
S S . 2.0
- S . 2.5

STEP 3 - Set the value to use to multiply the SYSTEM bus speed by. This value will be used to multiply the SYSTEM bus speed, and will set the PROCESSOR speed. One should target this multiple at or near the rated speed of the processor being used. Many processors can be "overclocked" or set to operate at speeds slightly higher than the processor part rating. Overclocking with the Beige G3, Blue and White G3, and G4 PCI Graphics motherboards is extremely easy: simply set the following multiple for the system bus speed to a higher value than the value that corresponds to the processor rating. Overclocking in smaller increments can be achieved by leaving the following multiple at the proper setting for a processor, and altering the PCI speed or multiple in the previous steps.

NOTE: The jumper settings for 8.5x, 9x, 9.5x, and 10x are unknown and I believe unsupported on Beige G3 motherboards. The 83.3mhz. and 87.5mhz. Bus settings are highly unlikely to work at all, although I have heard of one or two users successfully running a Beige G3 motherboard at the 83.3mhz. System bus speed.

x = unknown/undocumented, or highly unlikely to work.

Jumper Nr. . Multiplier
for Bus speed
. Resulting CPU clock speed
1 2 3 4 . . 66.7MHz Bus 70.0MHz Bus 75.0MHz Bus 83.3MHz Bus 87.5MHz Bus
- S S S . 3.0 = 200 210 225 250 262.5
- - - S . 3.5 = 233 245 263 292 306
- S - S . 4.0 = 266 280 300 333 350
S - - - . 4.5 = 300 315 337 375 394
- S - - . 5.0 = 333 350 375 416 438
- S S - . 5.5 = 366 385 413 458 481
- - S - . 6.0 = 400 420 450 500 525
S - S - . 6.5 = 433 455 487 541 569
S S - S . 7.0 = 466 490 525 583 613
S S S - . 7.5 = 500 525 562 625 656
- - S S . 8.0 = 533 560 600 666 700
- - - - . 8.5 = 566 595 637 708 744
- - - - . 9.0 = 600 630 675 750 787
- - - - . 9.5 = 633 665 712 791 831
- - - - . 10.0 = 667 700 750 833 875


EXAMPLE - The pairs indicated by red rectangles denote pairs with jumpers in place to "short" the connection between the left and right pins in the pair.


OVERALL JUMPER SETTINGS CHART (Colors correspond to detail charts above)

BUS speed
PCI speed
CPU speed
Multiplier
j1
(clock)
j2
(clock)
j3
(clock)
j4
(clock)
j5
(pci–mult)
j6
(pci–mult)
j7
(bus–mult)
j8
(bus–mult)
j9
(bus–mult)
66.66 MHz
33.33 MHz
200 MHz
3x
x
S
S
S
S
S
S
x
x
66.66 MHz
33.33 MHz
233 MHz
3.5x
x
x
x
S
S
S
S
x
x
66.66 MHz
33.33 MHz
266 MHz
4x
x
S
x
S
S
S
S
x
x
66.66 MHz
33.33 MHz
300 MHz
4.5x
S
x
x
x
S
S
S
x
x
66.66 MHz
33.33 MHz
333 MHz
5x
x
S
x
x
S
S
S
x
x
66.66 MHz
33.33 MHz
366 MHz
5.5x
x
S
S
x
S
S
S
x
x
66.66 MHz
33.33 MHz
400 MHz
6x
x
x
S
x
S
S
S
x
x
66.66 MHz
33.33 MHz
433 MHz
6.5x
S
x
S
x
S
S
S
x
x
66.66 MHz
33.33 MHz
466 MHz
7x
S
S
x
S
S
S
S
x
x
66.66 MHz
33.33 MHz
500 MHz
7.5x
S
S
S
x
S
S
S
x
x
66.66 MHz
33.33 MHz
533 MHz
8x
x
x
S
S
S
S
S
x
x
70.0 MHz 35.0 MHz 210 MHz 3x x S S S S S x S S
70.0 MHz 35.0 MHz 245 MHz 3.5x x x x S S S x S S
70.0 MHz 35.0 MHz 280 MHz 4x x S x S S S x S S
70.0 MHz 35.0 MHz 315 MHz 4.5x S x x x S S x S S
70.0 MHz 35.0 MHz 350 MHz 5x x S x x S S x S S
70.0 MHz 35.0 MHz 385 MHz 5.5x x S S x S S x S S
70.0 MHz 35.0 MHz 420 MHz 6x x x S x S S x S S
70.0 MHz 35.0 MHz 455 MHz 6.5x S x S x S S x S S
70.0 MHz 35.0 MHz 490 MHz 7x S S x S S S x S S
70.0 MHz 35.0 MHz 525 MHz 7.5x S S S x S S x S S
70.0 MHz 35.0 MHz 560 MHz 8x x x S S S S x S S
75 MHz
30 MHz
225 MHz
3x
x
S
S
S
x
S
S
S
x
75 MHz
30 MHz
263 MHz
3.5x
x
x
x
S
x
S
S
S
x
75 MHz
30 MHz
300 MHz
4x
x
S
x
S
x
S
S
S
x
75 MHz
30 MHz
337 MHz
4.5x
S
x
x
x
x
S
S
S
x
75 MHz
30 MHz
375 MHz
5x
x
S
x
x
x
S
S
S
x
75 MHz
30 MHz
413 MHz
5.5x
x
S
S
x
x
S
S
S
x
75 MHz
30 MHz
450 MHz
6x
x
x
S
x
x
S
S
S
x
75 MHz
30 MHz
487 MHz
6.5x
S
x
S
x
x
S
S
S
x
75 MHz
30 MHz
525 MHz
7x
S
S
x
S
x
S
S
S
x
75 MHz 30 MHz 562 MHz 7.5x S S S x x S S S x
75 MHz 30 MHz 600 MHz 8x x x S S x S S S x
83 MHz
33 MHz
250 MHz
3x
x
S
S
S
x
S
S
x
x
83 MHz
33 MHz
292 MHz
3.5x
x
x
x
S
x
S
S
x
x
83 MHz
33 MHz
333 MHz
4x
x
S
x
S
x
S
S
x
x
83 MHz
33 MHz
375 MHz
4.5x
S
x
x
x
x
S
S
x
x
83 MHz
33 MHz
416 MHz
5x
x
S
x
x
x
S
S
x
x
83 MHz
33 MHz
458 MHz
5.5x
x
S
S
x
x
S
S
x
x
83 MHz
33 MHz
500 MHz
6x
x
x
S
x
x
S
S
x
x
83 MHz
33 MHz
541 MHz
6.5x
S
x
S
x
x
S
S
x
x
83 MHz 33 MHz 583 MHz 7x S S x S x S S x x
83 MHz 33 MHz 625 MHz 7.5x S S S x x S S x x
83 MHz
33 MHz
666 MHz
8x
x
x
S
S
x
S
S
x
x

This document was assembled from information found on public web pages, and other documentation.
Any trademarks or copyrights are acknowledged as property of their respective holders.
Informational layout, images, and photos copyright 2001, 2002 William McLachlan.
Questions or comments contact William McLachlan - willy@wmld.com