The dual 2.5-GHz Power Mac G5: Unadulterated power

Although Mac fans might find it hard to believe, the dual 2.5-GHz Power Mac G5 does indeed exist. The new top-end Power Mac was officially unveiled in June, but only a few of them have trickled into customers' hands, and four months after its debut, it remains one of the rarest Macs out there (with the scarce iMac G5 not far behind).

Apple unveiled its latest Power Mac in June and promised that they'd be shipping by August. That date slipped into September, and even now, the top-of-the-line Power Mac, which goes for $2,999, is harder to find than hen's teeth. Order one online today from the Apple store and you'll find the estimated shipping is still three to five weeks out.

In other words, if you want one by Christmas, you'd better get in line now.

Thanks to Apple Computer's review program, I've been able to use one of the new Power Macs for the past three weeks or so, and I can tell you that if you need unadulterated processing power, the dual 2.5 is worth the wait. No, it's not quite the 3.0-GHz G5 Steve Jobs optimistically promised in 2003. But it offers more than enough warp-factor power for just about anything this side of genomic sequencing.

The review machine was packed with 4GB of RAM (it can take twice that amount), a 160GB Maxtor Serial ATA hard drive (with a 250GB Serial ATA hard drive available as a $100 built-to-order option), an ATI Radeon 9800 XT graphics card that offers 256MB of video RAM, and an 8x SuperDrive. (The standard graphics card is the ATI Radeon 9600 XT -- upgrading to the 9800 will set you back $300.) Like other Power Macs, it boasts the usual assortment of USB 2.0 and FireWire 400 and 800 ports, and an AirPort Extreme card for wireless networking.

This is Apple's first liquid-cooled Power Mac, and as best I can tell, the cooling system works as advertised. This is a good thing. The 2.5-GHz G5 chip runs very, very hot, requiring a variety of solutions to keep this machine from self-igniting. Apple touts four discrete "thermal zones," a variety of low-speed fans in each of those zones, 21 temperature monitors and the new, maintenance-free "closed-loop liquid cooling system."

I have to admit that it is a bit disconcerting to see a warning printed inside the Power Mac's case that suggests you unplug the computer right away and to "consult manual" should you see liquid leaking out. D'oh! But with those G5 chips fiery hot, the new cooling system was needed to keep the internal fans from spinning up to vacuum cleaner levels when you max out the processors.

That doesn't mean, however, that it doesn't get hot inside the all-aluminum case. After launching a little app called Temperature Monitor, I revved up the dual 2.5 and taxed the processors to see how hot it would get. Temperature Monitor reported the "CPU A and B die temperature" as 189.9 degrees and 184.9 degrees, respectively; the Memory Controller heat sink was reported as a toasty 172.6 degrees; and the drive bay came in at a relatively balmy 81.5. I could hear the fans rev up incrementally, pulling in cooler air, but they generated only a moderate amount of noise. Assuming that those temperatures are correct, the generally low level of fan noise was impressive.

Of course, ideally, with heat comes speed, and the new Power Mac offers plenty. How fast is this Power Mac? As I have done in the past, I ran the Xbench benchmarking app for a quick look at how those two G5 chips perform. The test yielded a score of 249, far above any other Power Mac I've used and notably faster than the other two machines I had on hand for comparison purposes. My iMac G5 (see story), with the 1.8-GHz G5 chip and a superfast 10,000-rpm hard drive, scored 165 on the Xbench test. My 12-in. Powerbook G4 (see story), with the 1.33-GHz G4 processor and a 5,400-rpm drive, got 125.

For comparison's sake, a first-generation dual 1.8-GHz G5 Power Mac yielded a score of 208 when I tested it with Xbench back in February -- and that was after installing the Western Digital Raptor hard drive I now have in the iMac (see story).

I also ran Cinebench for a different view of how the three machines stack up, with a greater focus on their graphics capabilities. On the PowerBook, which has a 64MB Nvidia card, the single-CPU render test took 118 sec.; on the iMac, which also has a 64MB Nvdia card, the test took 108.3 sec. And on the Power Mac, no doubt due to that 256MB ATI graphics card, the same test took just 73.6 sec. The muliple-CPU render test, not surprisingly, took even less: 42.6 sec.

What a difference video RAM -- and a second processor -- make.

To get an idea of what the Power Mac can do in the real world, I compared it against the other two machines on start-up time, simultaneous launch of five applications, an iMovie transition rendering and the application of the watercolor filter on a 46MB Photoshop image using Photoshop CS. The processor speed on all three machines was set at "highest."

The PowerBook took one minute flat to go from start-up chime to desktop; the iMac took 43 sec.; the Power Mac took 48 sec. I'm not sure why the Power Mac took a little longer to start up, unless the 4GB of RAM made for a lengthier memory check.

Launching five applications (Address Book, Adobe Photoshop CS, Mail, Safari and TextEdit) took 35 sec. on the PowerBook, 19 sec. on the iMac and 21 sec. on the Power Mac. Again, I'd have expected the Power Mac to be faster than the iMac. Kudos to the iMac.

Using iMovie, I added a four-second "scale down" transition between two digital video clips. On the PowerBook, this action took 14 sec. to complete, on the iMac it took 10 sec., and on the Power Mac it took just seven.

And finally, using Photoshop, I applied the watercolor filter to my PSD file. The PowerBook needed 8:14 to do the job. The iMac was a bit better, taking 7:32 to apply the filter. But the Power Mac practically flew through the task, taking just three minutes flat! Now, that's more like it.

As with all comparison tests, take these results with a grain of salt. I've found that Xbench can report slightly different results even when run back to back on the same machine. And while my real-world tests offer a glimpse at how the Power Mac performs relative to other machines, it's difficult to account for every variable that might be involved -- such as background processes that might be eating up CPU cycles. Having said that, I made sure each machine was running the same operating system (Mac OS X 10.3.5) and the same versions of the applications I used.

My conclusion? In processor-intensive operations, the Power Mac generally burns rubber, and it positively screams like a banshee when using software that takes advantage of both processors (such as Photoshop). If you're someone who does heavy-duty graphics or video, it'll save you a lot of time. And time is money.

For more leisurely users, Apple may have reached a point where it offers more speed in its top-end machines than you can realistically take advantage of. This is good news, in that you can save $600 by opting for Apple's midrange Power Mac, which offers dual 2.0 G5 processors, or even the just-introduced single-processor 1.8-GHz G5 model. It goes for just $1,499. With those kinds of savings, you can buy a heck of a lot of RAM, and Mac OS X loves memory.

If you've seen my earlier reviews of Apple hardware, you know I've always been a sucker for speed, and there's no doubt this is the fastest Mac I've ever used. Having said that, even I wondered at times if this desktop machine doesn't pack more power than even I need.

OK, I've thought about it.

It does offer more speed than I can use. But I still want one.