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Q
& A:
Power
Mac G4 Q & A:
Tech & Performance (2/3)
How
can I tell if a particular Power Mac G4 computer is
PCI-based or AGP-based?
According to the ever-helpful Tech Info Document #58418, the easiest way to determine if a particular Power Macintosh G4 computer is PCI-based or AGP-based by external inspection is to look at the sound ports on the back of the computer. On Yikes! PCI-based models, the sound ports are horizontally aligned, and on Sawtooth AGP-based models, the sound ports are vertically aligned.
The series of AGP-based systems announced on January 9, 2001 and discontinued on July 18, 2001 also can be distinguished from earlier AGP-based models by paying attention to port layout. Besides the extra PCI slot, the sound ports have been moved to the top, and the "soft" power plug has been removed.
The "Quicksilver" models, which are AGP-based, have the same port layout as the previous AGP-based models, but can be easily distinguished by the case design.
The "Mirrored Drive Doors" models are also AGP-based and can easily distinguished by the "mirrored finish" external drive bays and decorative indentions on the front reminiscent of the "Ventiports" on a 1949 Buick Roadmaster.
What is Velocity Engine? What makes the Velocity Engine improve performance?
The Velocity Engine is a 128-bit vector processing unit that is part of the PowerPC 74xx (G4) processor. Previously associated with expensive supercomputers, Apple explains that "162 new dedicated instructions integrated into silicon can be used to greatly accelerate intensive multimedia and math calculations. [The Velocity Engine] does this by working on a whole set of data simultaneously, rather than one data point at a time. The Velocity Engine also operates completely independent of both the integer unit and the floating-point unit, enabling all three units to process data at the same time."
What is a Level 3 cache? What makes Level 3 cache faster?
From Apple's own Power Macintosh G4 FAQ, "The L3 cache is high-speed, Double Data Rate SDRAM running at a data rate of [half the processor speed] that enhances processor function by providing fast access to data and application code at up to 4 GB per second. The L3 cache is even more effective because it has a dedicated bus to the processor, so the full 4 GBps is always available without bottlenecks caused by other data. The high speed of the L3 cache with its dedicated bus, compared to the lower speed and shared bus of main memory, allows the processor to receive data up to five times faster than from main memory. This low latency keeps the processor constantly fed with data, so it isn't sitting idle while waiting for the next task to arrive. This ensures better utilization of the processor, resulting in better overall system performance."
What graphics card is provided by the Power Mac G4 series?
Prior to December 2, 1999, the Power Macintosh G4 series shipped with the 16 MB ATI Rage 128 video card. From December 2, 1999 to January 8, 2001, all models in the Power Macintosh G4 series shipped with the 16 MB ATI Rage 128 Pro video card. Whereas the Power Macintosh G4 systems announced on January 9, 2001 and discontinued on July 18, 2001 shipped with either a 16 MB ATI Rage 128 Pro or a 32 MB NVIDIA GeForce2 MX video card.
The original "Quicksilver" series, announced on July 18, 2001 and discontinued on January 28, 2002, shipped with either a pre-installed 32 MB NVIDIA GeForce2 MX or 64 MB NVIDIA GeForce2 MX TwinView, or a build-to-order 64 MB NVIDIA GeForce3 video card. The second "Quicksilver" series, announced on January 28, 2002 and discontinued on August 13, 2002, shipped with either a pre-installed 32 MB ATI Radeon 7500, a 64 MB NVIDIA GeForce4 MX, or a build-to-order 128 MB NVIDIA GeForce4 Titanium video card.
The Power Macintosh G4 "Mirrored Drive Doors" models shipped with either a a 32 MB NVIDIA GeForce4 MX (AGP 4X) or a 64 MB ATI Radeon 9000 Pro (AGP 4X) video card.
It is worth noting that the graphics cards pre-installed beginning on July 19, 2000, include the ADC (Apple Display Connector), which carries analog and digital video signals, USB data, and power in the same cable to reduce clutter.
How fast are dual-processor Power Mac G4 models compared to single-processor models?
According to Apple-published timed tests using Photoshop 5.0, the discontinued Power Macintosh G4/500 DP took 36 seconds to perform eight different tasks, while the also discontinued Power Macintosh G4/400 (2) took 51 seconds to perform the same tasks.
The series of Power Macintosh G4 models announced on January 9, 2001 and discontinued on July 18, 2001 include one dual-processing model, the Power Macintosh G4/533 (DP), as a custom-configured option. Apple-published benchmarks comparing this system to single processor models, were not released, but may be added to this Q & A at a later date.
The original "Quicksilver" models include one dual-processor model, the Power Macintosh G4/800 DP QS. According to Apple-published benchmarks, this dual processor model is roughly 20% faster than the single processor Power Macintosh G4/867 QS running a suite Photoshop tests. The second "Quicksilver" models introduced on January 28, 2002 and discontinued August 13, 2002, also include one dual-processor model, the Power Macintosh G4/1.0 DP QS. According to Apple-published benchmarks, this model is approximately 20% faster than the single processor Power Macintosh G4/933 QS running a suite of Photoshop tests.
The first Power Macintosh G4 "Mirrored Drive Doors" series, introduced on August 13, 2002 and discontinued on January 28, 2003, are all dual-processor systems. Apple released benchmarks comparing the dual-processor Power Macintosh G4/1.25 DP "MDD" to the original Power Macintosh G4/500. According to Apple, the original Power Macintosh G4/500 has a peak performance of 3.7 Gigaflops and the Power Macintosh G4/1.25 DP "MDD" has a peak performance of 18.3 Gigaflops, more than five times as fast. Apple also reported that the Power Macintosh G4/1.25 DP "MDD" is "50% faster than the Quicksilver from [the previous] Summer". The second Power Macintosh G4 "Mirrored Drive Doors" series, introduced on January 28, 2003 and discontinued on June 23, 2003, includes two dual processor models, a revised version of the Power Macintosh G4/1.25 DP "MDD" and the Power Macintosh G4/1.42 DP "MDD". Apple-published benchmarks show that the then top-of-the line Power Macintosh G4/1.42 DP "MDD" had a peak performance of 21.0 Gigaflops, roughly 25% faster than the single-processor Power Macintosh G4/1.0 "MDD" introduced at the same time, and a whopping 204% faster than the original Power Macintosh G4/500.
Dual-processing can make a big difference in the performance of MacOS X and in applications that are designed to take advantage of the added performance of a second processor, otherwise the performance gain is minimal.
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