Hands-on details on Mac Pro (long)

Here's some of the deep-dive copy from the Mac Pro review that I reserved for my on-line readers. I'm sure I made some formatting errors in copying it from [product W] to Ecto. I've deleted some text that points to the conclusion of the review. I'm not messing with you there. I can't share a review's conclusions prior to its publication, and I ask that you don't presume a conclusion from what you'll read here.

The best sub-$5,000 workstation ever made, Apple’s Power Mac G5 Quad, has been supplanted in Apple’s lineup by Mac Pro, a quad-core workstation based on Intel’s newest 64-bit Core Microarchitecture Xeon processor. Intel’s marketing promotes the new dual-core Xeon, nicknamed Woodcrest, as being faster and yet more power-efficient than the Netburst (Pentium 4) Xeon CPUs that preceded it. Woodcrest certainly is fast by Intel standards, thanks to its huge cache and cranked-up front-side bus. Intel and all of its OEMs are delighted about Woodcrest, but it nets Apple no advantage. It looks like Apple is setting Mac Pro up to be just another mid-tower Woodcrest box in a landscape choked with mid-tower Woodcrest boxes.


Mac Pro shares most of the external characteristics of Power Mac G5 models. I got my first tip-off that Mac Pro follows in the Power Mac tradition when I lifted it: It weighs a ton. Well, 60 pounds to be exact. Remember, the overall chassis design was cooked up (no pun) for 64-bit PowerPC, renowned for being fast as hell and twice as hot. Just before this chassis made the jump to Intel, it contained a pair of dual core, 64-bit IBM PowerPC CPUs, replete with massive heat sinks, routed airflows and a fluid cooling boost for those times when China Syndrome threatened. Workstation users are accustomed to trading heat and noise for performance, but to Apple's considerable credit, Apple’s engineers made Power Mac G5 Quad run markedly quieter than top-end Netburst Xeon, Opteron and RISC workstations. Design victories scored in Mac Pro make Power Mac G5 Quad no less stunning a machine.

So it’s almost sad to remove Mac Pro’s side panel, which still requires only the lifting of a lever on the back, and see all that heat and noise control ingenuity gone. The Mac Pro’s case, which is more holes than surface at the front and back, seems to have started life as empty box full of moving air. Apple wasn’t going to ditch the indestructible, interference-immune and familiar Power Mac case, so it set its engineers loose on useful ways to fill it.


Tricking it out

Apple’s Woodcrest motherboard is not a wee twist on Intel’s reference design, as is the prevailing standard among Intel’s OEMs. You needn’t take up my appreciation of circuitry as art to learn this yourself: Apple knows that workstation users are defined, first and foremost, by their insatiable desire for places to plug things in. Mac Pro’s back panel features an insane variety of connectivity ports: Three USB 2.0, two FireWire (one 800 Mbps and one 400), optical digital audio in and out, line-level analog audio in and out, and dual gigabit Ethernet. And just to cover the risk that users would run out of sockets for things, Mac Pro’s front panel has two FireWire (again, one 800 Mbps), two USB and one headphone/line level analog audio output ports.

Inside, Apple took advantage of the cavernous chassis to keep riffing on the “you want it, we got it” theme. The system has four full-length PCI Express slots, one of which is double wide to accommodate large graphics cards without wasting a usable slot. One of the primary criticisms I expressed related to Power Mac G5 was the poor design of the card cage, specifically, that the tiny, non-standard screws holding the cards in place stripped too easily—an unrecoverable condition, I learned—and were too weak to hold cards with heavy cables that would be frequently plugged and unplugged. Now Apple holds Mac Pro’s cards in place with a single metal panel secured by two thumbscrews. Little things mean a lot to people like me who demand unbreakable hardware.

Mac Pro adds room for a second parallel ATA optical drive, including a second garage door that opens and closes when discs are inserted and removed. Mac Pro uses full-sized, tray loading drives, so you can add your own as long as you can pop the drive’s face plates off. Of course, you can also snap the tray when you don't know it's out (the tray is black and easy to overlook), a fact that makes slot-loading drives look rather smart. On the other, other hand, slot-loading drives can only accept 5.25-inch discs.

Will you be having the 250 gigabytes, or the three terabyte special?

Hearing the cry of workstation users that they never have enough storage, Apple made room for four Serial ATA drives inside Mac Pro’s chassis. That’s not unheard of; a full-sized tower Opteron workstation in my shop has five drive bays. But Apple put six bays in a mid-tower box by lining up a row of four easily removable, zero cabling drive trays just above the expansion card area. The trays are precisely the size of 3.5-inch hard drives and—get this—Apple does not require that you purchase Apple-branded drives. All Mac Pros come with four trays, and you can fill the empty ones with off-the-shelf SATA drives at will. SATA drive densities are rising at a dizzying pace, and with the present ceiling at 750 GB, you can stuff a Mac Pro with a remarkable 3 terabytes of storage. You know you’re a true workstation user if you greet that figure with, “is that all?” Yes, you’ll have to make do with 3 TB for now. (at this writing, Apple maximum drive size is 500 GB)

Mac Pro uses 667 MHz fully-buffered DIMM (FBDIMM) memory, as is standard with Woodcrest systems. Using a very fast serial bus, FBDIMM has a lot of potential, but its advantages over more widely-used DDR2 are sometimes exaggerated. However, FBDIMM serves Woodcrest's shared-bus design well, because there wasn't much more parallel bandwidth Intel could pull out of its design. As is generally true, FBDIMM trades performance for heat and power draw, but in a two-socket design like Mac Pro the difference is insubstantial.

Apple adds an implementation twist to its memory that might slip by most observers, but which represents a radical change for the better in workstation and power desktop system design. Instead of fixing FBDIMM sockets to the motherboard, as is the norm, Apple placed the memory sockets and supporting circuitry on removable riser cards, minicomputer-style. Like the hard drive trays, the memory risers are held in place with friction and extremely easy to install and remove. There’s no more laying your computer on the floor to mash skinny DIMMs into stiff sockets on a fragile motherboard.

The only disadvantage to easily removable disks, memory and expansion cards is that even though they are not hot-pluggable, meaning they cannot be removed from a powered-up system without the likelihood of damage, they will pull out while the machine is running. The drives have an interlock with the side panel lift lever; you have to raise it to a higher position to pull any of the drives, reducing the likelihood of accidental removal, but you can raise the lever that while the machine is on. There is one of those situations where Apple should relax its policy against LEDs. There's no tip-off from inside the Mac that it’s powered up. There isn’t a single LED on the motherboard, the fans are not readily visible and the machine runs virtually silent. Further, in sleep, the machine seems to be powered down, but pulling memory while it's in this state is just as dangerous as if Mac Pro were in active use. Just get in the habit of pulling the power cord before you open the case.

If you're feeling frisky, get in there with a scope and a soldering iron and poke around for a place from which to tap 5V or 3.3V. It'll be good practice for you if you're the type who plans to follow instructions on the 'net for overclocking this puppy. Apple scowled at me when I asked if Mac Pro's CPUs are field-upgradable. The official word: "I don't think it's possible, but if it is, we won't support that." Given that the CPUs and heat sinks are on risers, too, field performance upgrades and botched attempts at same will be real issues after Mac Pro gets traction in the gaming market, in which area I believe Mac Pro is a strong contender. Apple gets a much bigger installed base, but also a subculture of people who figure out ways to avoid buying Apple's next model. You have to take the bitter with the better, and for my money, it's better to stay wide open. At least sites with the hardware hacks will sell Mac Pros to people who want to try the hacks out themselves.

Apple’s memory and CPU risers make Mac Pro’s cooling much, much simpler and quieter. The memory risers are several inches apart for maximum airflow, and they share the straight line push-pull fan pair that cools the Xeon CPUs. The CPU modules, which are concealed under a plastic panel, are also mounted perpendicular to the motherboard and topped with generous aluminum heat sinks. The heat sinks do not have small, buzzy top-mounted fans.

Air flow is generated by three massive fans, two up front and one in the back. The front and back panels are, top to bottom, a honeycomb in which roughly half of the space is open to air flow. The full-height grilles wrap around a little at the the top allow iMac-style convection cooling when the system is not under load. As a point of interest, the front, top and back of Mac Pro are fashioned from a single piece of aluminum. It doesn't just look slick. It cuts vibration and airflow leakage.

Feeding Mac Pro

Power consumption is on everyone’s minds. Apple’s 32-bit iMac set records in my tests by operating at about 85 watts, including the display. Mac Pro's power efficiency is entirely in line with other Woodcrest systems I've seen. Apple adds relatively little magic here, and I don't know how much opportunity Apple had that it didn't use. Intel's power sparing can be automatic and OS-directed, so I'm hopeful that Apple will use firmware and OS updates to push the idle power utilization down from the 220 watts I measured in my tests. That figure does not include the display.


In sleep, power draw falls to about 7 watts with Ethernet ports actively listening for administrative commands. It took the Mac Pro eval box with 4 GB of RAM only four seconds to wake from sleep, so sleep mode ought to be used liberally. Unfortunately, the idle timer used to trigger sleep is reset only by the keyboard or mouse, so background renders, compiles and the other non-interactive operations common to workstation use might cease when the user walks away. However, sleep mode can be triggered from a script, and Mac Pro will sleep and wake on a user-settable schedule. Instead of disabling sleep out of frustration, find a way to make it work for you. It matters.

Floating some points and flinging some pixels

Performance ranks rather high among things that workstation users desire in excess. Given the same CPU and core logic, Woodcrest systems from PC vendors A, B and C, running at the same clock speed, will turn in identical computing performance. The hilly playing field that Apple set up with PowerPC is now flat; on everyday benchmarks, anything can run as fast as a Mac workstation. [...]

Mac Pro can hold two or three more hard drives than users expect to find in a workstation or power desktop, and I’ve found that one of the best uses for that gravy is a RAID 0 (simple interleave) stripe. OS X Tiger, which ships with Mac Pro, makes child’s play of creating easily restorable drive images on external storage. So I created a three-drive RAID 0 set on Mac Pro and set the machine to back itself up to a parity-protected Xserve RAID volume during the wee hours. When OS X Leopard ships, that protection will be continuous and genuinely automatic. People understandably get nervous about striping without parity, but if you’re a workstation user whose disks are constantly active, the performance boost of RAID 0 for work in progress files shouldn't be disregarded as long as you balance the risk.

Apple takes a more liberal approach to thermal thresholds than its competitors do. By that, I mean that Apple does not throttle the CPUs down when they get a little warm, hot or downright incandescent. Like all Macs, when Mac Pro is running full-out with a maximum compute load, it will hold top CPU clock speed and voltage past what other vendors consider to be the thermal danger zone. Apple does this without cranking the fans up to intolerable noise levels. I made Mac Pro go loud by letting the room heat up to over 90 degrees. But in ambient temperature that’s more favorable to human existence, Mac Pro keeps itself quiet.

I ran, and am still running, a number of performance and endurance tests, but the simplest one that hits both the CPU cores and the graphics processing unit (GPU) is SPECviewperf. The savvy will point out that SPECviewperf is strictly a test of the speed at which pre-computed 3-D scenes can be displayed. However, SPECviewperf 8.1 turns in usefully varying CPU usage patterns that tend to favor the 60 to 90 percent utilization window. SPECviewperf is a single process, single threaded benchmark, so the thing to do is run multiple simultaneous instances, one per core. All I cared about was noise and power consumption, and with four SPECviewperf 8.1 processes running side-by-side, Mac Pro ate around 300 watts. The fan never got loud, and the frequency and timbre of its noise is actually pleasant and easy to block with a unidrectional ("noise reducing") microphone.

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