Officially the CarrierZIF manual documents only bus speeds from 40 to 60MHz, but a reader did some investigation and discovered additional settings up to 66MHz:

"Mike,
I have a PowerCenter that originally had a clock speed of 60.2MHz. Naturally, I assumed that PowerComputing made there specs a bit better than that though. Unfortunately, XLR8 didn't take into account bus speeds above 60MHz. I charted the current switch setups and came up with an extension to the current chart. You will find the chart attached (in html format). You're welcome to post it where appropriate!
Anthony D. Saxton
LnA Concepts "

About The Table:

In the table below the 'Jumpers' row refers to XLR8 ZIFs that have jumpers on the ZIF module, some models rely on the CarrierZIF for Bus/CPU ratio (as do many OEM/Apple ZIFs). The Blue column lists bus speeds; adjacent to it are the switch settings for those speeds. I've not verified this personally yet but thank Anthony for the info!

CPU Multiplier

4.5

5

5.5

6

6.5

7

7.5

8

10*

Jumpers -->

I:::

:I::

:II:

::I:

I:I:

II:I

III:

::II

I::I

Switches-On-->

12

11

10,11

10

10,12

9,11,12

10,11,12

9,10

9,12

60.6
61.0
61.6
62.0

4,5,7,8
2,5,7,8
2,3,5,7,8
1,4,5,7,8

 272.7 
274.5
277.2
279.0

 303.0 
305.0
308.0
310.0

 333.3 
335.5
338.8
341.0

 363.6 
366.0
369.6
372.0

 393.9 
396.5
400.4
403.0

 424.2 
427.0
431.2
434.0

 454.5 
457.5
462.0
465.0

 484.8 
488.0
492.8
496.0

 606.0 
610.0
616.0
620.0

62.6
63.0
63.6
64.0

1,3,4,5,7,8
1,2,3,5,7,8
4,5,6
2,5,6

281.7
283.5
286.2
288.0

313.0
315.0
318.0
320.0

344.3
346.5
349.8
352.0

375.6
378.0
381.6
384.0

406.9
409.5
413.4
416.0

438.2
441.0
445.2
448.0

469.5
472.5
477.0
480.0

500.8
504.0
508.8
512.0

626.0
630.0
636.0
640.0

64.6
65.0
65.6
66.0

2,3,5,6
1,4,5,6
1,3,4,5,6
1,2,3,5,6

290.7
292.5
295.2
297.0

323.0
325.0
328.0
330.0

355.3
357.5
360.8
363.0

387.6
390.0
393.6
396.0

419.9
422.5
426.4
429.0

452.2
455.0
459.2
462.0

484.5
487.5
492.0
495.0

516.8
520.0
524.8
528.0

646.0
650.0
656.0
660.0

Related Links:

• First CarrierZIF Full Review
  (7 pages including installation/troubleshooting tips and tests in 3 Mac models)

• CarrierZIF First Look

• MAChCarrier 450 Review (10X Ratio G3/450 CarrierZIF model)

• Illustrated CarrierZIF Setup Guide (ZIF compatibility, important setup notes, speed settings and more)

• XLR8 G4 in a CarrierZIF (First G4 upgrade review anywhere in the world!)

• Other CPU Card (ZIF/PCI Slot/Other) Reviews and Related Articles

• Rate Your G3 Card searchable database of over 2000+ owner reports including PowerBooks, Nubus, L2 Cache slot. CarrierZIF and ZIF models. There's even overclocking reports with Apple G3 models (Beige/B&W/iMac)