Pimp My Ride – Upgrading a Power Macintosh 7300/200 to a 400 MHz G3

This is part two of our “pimp my ride” series, in which we undertake  performance upgrades to various subsystems of a Power Macintosh 7300/200. In the first part of this series, we upgraded the 7300/200 with an ATI Radeon 7000 Mac Edition video card, and found the results largely uninspiring. In this post, we upgrade the CPU from the stock 200 MHz PowerPC 604e to a 400 MHz G3.

The CPU is the heart and soul any computer, and a capacity increase in this area should certainly among the highest impact updates a user can make. In my case, my Power Macintosh 7300/200 shipped with a 200 MHz 604e, and was a very capable machine in this configuration. Nonetheless, I had two CPU updates available, both from Sonnet: a 500 MHz G3/1M and a 400 MHz G3/1M. Conceptually, both should have been able to more than double the performance of the 7300, and as we shall see, this was indeed the case.

I am sure that it will come as no surprise to anyone that I started with the 500 MHz card. Installation was simple enough. I located and loaded up the Sonnet Processor Upgrade extension (ce_install_v31.sit) and powered down the machine. I removed the cover, extracted the original 200 MHz card …

2015-10-22.1124, Power Macintosh 7300 with Original 200 MHz CPU in Place

… and slotted the new 500 MHz card into its place. The new card was a curiously small form factor, but It declared itself to be a Crescendo G3, and all of Sonnet’s literature said that this compatible with a Power Macintosh 7300 and so I proceeded. Suspecting that trouble might be in the offing however, I did not replace the cover of the 7300.

2015-10-22.1126, New 500 MHz G3 CPU for Power Macintosh 7300

It slotted into place just fine…

2015-10-22.1127, New 500 MHz G3 CPU Installed, Power Macintosh 7300

…but trouble was indeed in the offing. My attempts to start the machine up after the install were a complete failure. I could hear the machine power on, but there was no start up chime, and no other overt signs of life. I left the machine sitting like that for some time (several minutes), just in case it was running RAM tests, but it remained deaf and mute, and eventually I turned it off.

I reseated the card and retried the start up several times, but always to no good end. I tried zapping the PRAM and restarting, but again, no joy. Finally, I was left to decide that this was either an unsupported card for the 7300, or it was defective. Happily, I had a fallback, the 400 MHz upgrade card I mentioned above, and I dropped back to that.

This card was more or less the same form factor as the original 200 MHz card…

2015-10-22.1134, New 400 MHz G3 CPU for Power Macintosh 7300

…and slotted in easily.

2015-10-22.1136, New 400 MHz G3 CPU Installed, Power Macintosh 7300

When I pressed the Power button this time, the machine sprang to life instantly, issued a robust start up chime and dropping directly into the boot sequence. This sequence was observably faster than before, and quickly yielded a fully booted desktop.

Alright then – so far, so good, but was it running at 400 MHz? Sonnet prides itself on being a no hassle upgrade. As their literature says, “No Switches, No Control Panels, Just Fast”. As you might expect therefore, there was no control panel to look at to verify the CPU speed. Sonnet did however provide a program called Metronome, which measures and reports the speed of the CPU. I found Metronome in my Apple Menu items and ran it. As you can see below, it reported a clean 400 MHz. Sonnet was right. No muss, no fuss, just fast.

Sonnet Metronome, 400 MHz

Apple System Profiler gave me an identical result:

Apple System Profiler, 400

OK, the CPU was running cleanly at 400 MHz. I was particularly interested in this since in the past, I had upgraded a Power Macintosh 7500/100 with a Newer Technology brand 400 MHz G3, only to get a less than advertised 366 MHz from it.  I am guessing that some form of clock auto scaling was responsible for this, perhaps as the card did its best to multiply the system clock, but it always left me wanting… I had paid for 400 MHz and received only 366 MHz. It still made a HUGE difference, but it wasn’t everything I had been expecting. In this case, I was pleased to see that my new Sonnet upgrade was delivering the full 400 MHz I had paid for.

So, how fast IS 400 MHz relative to the initial 200 MHz? I tried a few very subjective tests, and was impressed with the results. Image decoding in JPEGView was significantly faster than before. My ThumbsPlus image cataloger and viewer seemed to race through images in a way I could only have dreamed of before the upgrade. This was all encouraging. It was time for some objective testing.

The system now booted in 125 seconds, vs. the original 177 seconds. This was faster, but not as much faster as I might have expected. It seems to me that this must be reflective of a boot process that is bound not just by CPU but also by disk I/O. I am guessing that having improved only one of these two factors, I did not get the maximum benefit.

Application loading really sparkled however. Adobe Photoshop 7.0 now loaded in 31 seconds, vs. the original pre upgrade time of 1 minute and 30 seconds, a really nice 3x boost. Image decoding improved quite a bit as well. There are three images that I had used in benchmark testing some time ago, and still had the previous recorded decode and display times for. After the 400 MHz upgrade, I tested them again and the new results looked like this:

  • Image One: 3.5 seconds (vs. the original 7 seconds)
  • Image Two: 3 seconds (vs. the original 4 seconds)
  • Image Three: 3 seconds (vs. the original 6 seconds)

Overall, I would summarize the above as a roughly 2x boost, which is not quite as much as I might have expected, when doubling the clock and going from a 604e to a G3 with 1 MB of backside cache, but there you have it.

To offset that minor disappointment however, there was a hidden bonus in this upgrade, quite aside from the new, snappier behavior of the system. The system ran quieter now as well! The 7300 has variable, temperature controlled fans, and I have always noted that as the machine warmed up and internal case temperatures stabilized, the fans would ramp up somewhat and the machine would get noisier. This was  not the case post upgrade. Clearly the new 400 MHz G3 must run cooler than the older 200 MHz 604e, resulting in less need for cooling and thus quieter operation overall.

So, in summary, bumping up the CPU from a 200 MHz 604e to a 400 MHz G3 produced excellent and very noticable results. The machine now booted faster, applications loaded faster AND ran faster, and as a final bonus, the system ran cooler and quieter. I’ll call this upgrade step a big win all around.

Up next, and the last upgrade step in this series, is an upgrade to the hard drive, from an original SCSI drive to an ATA-66 interfaced IDE hard drive. Read on to see the impact of this change.

2 thoughts on “Pimp My Ride – Upgrading a Power Macintosh 7300/200 to a 400 MHz G3

  1. Did you ever figure out what was up with that smaller sized 500mhz module? Because I’m looking at getting one for my PM8600, and I want to know if there’s compatibility issues, or if yours was likely just faulty.

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