Originally Web posted Wednesday, 27 October 2004.
Content last modified Wednesday, 9 May 2012 .
External links last verified Wednesday, 9 May 2012.

MAXpowr G3 Processor Card

DIP Switch Settings and More

Notwithstanding the excellent information i found when searching xlr8yourmac.com and other WWW pages, nowhere could i find an explanation of what the dip switch settings on my MAXpowr G3 300 MHz CPU/200 MHz cache Internal Processor Upgrade Card did, nor recommended settings beyond some very skimpy information in the otherwise excellent Newer Technology manual.

Unless/until better information comes along, this page attempts to fill the knowledge gap by presenting the results of some tests i did. If anyone reading this page, especially Newer Technology engineers and/or technicians, cares to contact me with additional information, i will gladly add it to this page.


My motivation for spending the time diddling with the dip switch settings was to improve stability and eliminate some very obvious and distracting video artifacts. The Newer Tech MaxPower Pro 250MHz PPC750 card Review page at xlr8yourmac.com discusses video artifacts not being a problem at color depths other than Thousands. While i have seen this in other circumstances, this was not the case with my 8500/MAXpowr G3 300: problems were at least as bad, if not worse, at Millions of colors, and were visible even with 256 colors.

The same review and other sources mention that the problem is restricted to built-in Macintosh video, and is totally eliminated when an add-on PCI video card is used. This is true, and is due to the separate clocking of the PCI bus. The onboard video is clocked at the processor bus speed, which is typically altered (sped up) by accelerator cards. The artifacts are not restricted to cards from Newer Technology by any means! Not wanting to put more money into this mid-1990s Macintosh, nice as it is, and using the video glitching as a “warning canary” for actual and potential stability problems, i chose to attempt to make the stock onboard video glitch-free.

Also mentioned on the same review page is lowering processor bus speed to eliminate the artifacts. While the MAXpowr Control control panel offers all sorts of nifty adjustments, none of them alter processor bus speed. Not coincidentally, no combination of control panel settings i could find solved the video artifacts problem.

Test Methodology and Details

Testing of the various dip switch settings was only performed on one configuration:

Previous testing revealed that the control panel settings had no effect on CPU clock speed, nor bus speed… just MAXpowr backside cache speed. Testing consisted of looking for visual artifacts around startup icons during startup, and repeatedly moving a single Finder window on the desktop. The latter test was especially good at revealing any video artifacts in a very short period of time.

No effort was made to be consistent about resetting NVRAM/PRAM. I found no difference in results whether those items were reset or not, as long as the MAXpowr card remained in its socket. The machine was cold booted, tested for glitches, shut down, then the dip switch settings changed and the process repeated. There were occasional crashes into MacsBug due to some aspect of the Control Strip during startup. No attempt was made to reproduce these crashes nor troubleshoot them. If there was to be a crash, it happened when the “incorrect date” dialog was displaying. Testing was done with an external power supply in place of the normal PRAM battery, hence the date being reset to its default. Casual inspection hints at the crash being due to times where the control strip preferences file was last modified at a time and date in the future, relative to current (incorrect) system time.

DIP Switch Settings Test Results

Speeds are in MHz, as displayed by NewerTech Gauge PRO 1.1
DIP Switch Settings CPU Speed Cache Speed Processor Bus Speed Memory Performance Speed Comments
All Off 302.1 201.4 46.5 52.5 Recommended (shipping) NewerTech default setting, per manual
1 On, Rest Off 302.1 201.4 46.5 52.5 No discernable change in operation vs. all Off
2 On, Rest Off 300.0 200.0 50.0 50.1 The “nice round numbers” setting. Highest bus speed found.
3 On, Rest Off 300.7 200.4 43.0 50.1 No video glitching! Slowest, safest bus speed found.
4 On, Rest Off 302.1 201.4 46.5 52.1 No discernable change in operation vs. all Off
1&4 On, 2&3 Off 302.1 201.4 46.5 52.7 NewerTech’s recommended setting for Mach 5 systems (8600, 9600). Other than the control strip crash, no discernable change in operation vs. all Off
2&3 On, 1&4 Off 302.1 201.4 46.5 52.7 Other than the control strip crash, no discernable change in operation vs. all Off. I expected another bus speed.
1&2 On, 3&4 Off 300.0 200.0 50.0 50.2 Not discernably different than having just #2 On
1&2 Off, 3&4 On 300.7 200.4 43.0 50.1 No video glitching
1&3 On, 2&4 Off 300.7 200.4 43.0 50.1 Video glitches appeared with this setting, even with the slowest processor bus speed
2&4 On, 1&3 Off No startup: Flashing ?
1,2,3 On, 4 Off 302.1 201.4 46.5 52.6 No discernable change in operation vs. all Off
1,2,4 On, 3 Off 300.0 200.0 50.0 50.2 Not discernably different than having just #2 On
1,3,4 On, 2 Off 300.7 200.4 43.0 50.2 No video glitching
2,3,4 On, 1 Off 302.1 201.4 46.5 52.7 No discernable change in operation vs. all Off
All On No startup: Flashing ?


Life went on, and the very same Power Mac 8500 and MAXpowr G3 processor card system sat unused for many years. In the early 20teens, the Mac would no longer start, not even chiming upon application of power. The following are some troubleshooting notes from April 2012, when i once again got the machine going.

No Chime, No Boot with MAXpowr G3 card. Works fine with stock Apple processor card.
Clean the contacts on the MAXpowr card Thoroughly with Caig DeoxIT Red followed by Caig DeoxIT Gold. I used the pure liquid DeoxITs. Even though the contacts looked pristine gold before cleaning, a good bit of stuff came off on the cotton swabs during two full treatments with Red (less on the second treatment), followed by not much with Gold. This contact cleaning brought the card from unusable to operational and stable. Note that previous to the cleaning, the card had been inserted and removed multiple times in two different otherwise-working 8500s, so frictional cleaning is likely to be insufficient. It would not hurt to additionally cycle the DIP switches through their various positions before restoring them to the normal setting for your particular Mac.
Intermittent Freezes, no matter what control panel settings etc. are used
Try stripping the machine down to no hard drive and “nuclear” PRAM reset (battery removed for a sufficiently long time, ideally overnight). Start the machine with the case open, and a pointing device attached. When the Mac reaches the flashing ? stage, move the mouse and ensure that the cursor moves. Now, gently wiggle the MAXpowr card. If the cursor freezes (machine locks up), clean the contacts as described above. (This happened to me. If wiggling does not induce a freeze, you have a different problem than i had.)
Boots with Mac on its side, but not in normal orientation
This will probably only apply to tower models like the 8500: gravity pulls on the card and alters the contact pressure/alignment. This too happened with my card and 8500, and at first was puzzling. Once again: dirty contacts. Clean as described above.

Other (possibly) Helpful Information

By extrapolation, the above should be true on other PowerSurge Macs (7500/9500/7600/8600/9600 etc.) and other OSes valid for these models. I know these to be true via direct experience on an 8500.

About that Manual…

In late April 2012, it occurred to me to see whether the original NewerTech manual was available online. I ran across a quite recent (at the time: early April 2012) thread on 68k Macintosh Liberation Army indicating that the manual was not readily available online. Through the kindness of a dear, departed former Maccer and MAXpowr G3 owner, for years i have had a photocopy of her original manual. I got busy with the scanner, Photoshop (5.0 LE), and Acrobat (5.0.5, all this on an unaccelerated PowerMac 9600/350 running my tweaked OS 9.1 which i call OS 9.1+), and here we are:

NewerTech MAXpowr G3 PowerPC 750 Internal Processor Upgrade Card for Power Macs and Clones original installation and use Manual

This is a 51 page PDF made from scans of the photocopied paper manual i was given. The photocopying was so-so, so don’t expect miracles. It ought to be legible where it matters. I specifically used an old version of Acrobat in hopes of generating a PDF format old enough to be generally readable on Vintage Macs. It came out as PDF version 1.4 (new features concurrent with Acrobat and Reader 5), which is newer than i wanted, but it basically works fine in Acrobat Reader 4.05a under OS 9.1/PPC, other than the thumbnails fail to navigate (but the bookmarks work!).

Before anyone gets too excited, please understand that most of the manual goes into great detail regarding how to get inside various Apple and clone Macs of the time, and physically how to change the processor card, aimed at an audience of people who have never done this before. Hobbyists and other skilled users are likely to be disappointed (as i was) at the lack of technical specifics. In fact, i can probably save you some time (and maybe a download) by summarizing the salient points:

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