Some Thoughts on the Mac Pro Design

Question

The design of the Mac Pro raises some interesting questions, and I'd like to know if anyone on this forum has insight on these issues.
First, the use of riser cards for main memory is unusual in a consumer or small-business oriented PC design. Designers normally try to avoid this architecture because it adds cost and potentially slows the system. The higher cost comes from the additional connectors, mechanical support hardware, and interface circuitry necessary to drive the memory chip data across the logic board connector. (That's why the Mac Pro memory modules are fully buffered.) Placing the memory slots on the logic board (as in the G5 design) is significantly less expensive. Riser cards also have reduced memory bandwidth due to the additional capacitance and inductance associated with the longer signal traces between the memory and the CPU. The riser card approach is usually used only when there are packaging constraints (i.e., space constraints) that preclude placing the memory chips on the logic board, or when there is some plan to allow future expansion of the system by adding new hardware using the riser board connectors (e.g., additional processors or other devices).
The only explanation that I can find is that Apple was forced to this architecture by packaging constraints imposed by the carry-over tower architecture.
Second, the use of ECC memory in a consumer or low-end business machine is also unusual. ECC memory is typically used for high-reliability computers that process data for non-consumer applications where the consequences of corrupted data are substantial (as in computing at financial institutions, control systems for medical devices, etc.). ECC memory offers a level of data integrity, but is generally higher cost (more chips) and slower (it takes time to compute and compare the ECC codes) than non-ECC systems. Since Apple is using ECC, it would seem that they are either planning to sell Mac Pros in to high reliability applications, or they know something about memory bit failure rates that we don’t. The actual memory die used in the Mac Pro memory modules are standard DDR2 5300 parts, and are the same as those used in the Macbook Pro.
The overall design of the Mac Pro positions it well for use as a work station, and perhaps that was Apple's intent.
The price of the Mac Pro is remarkably low when compared to machines from Dell or Gateway. The good news seems to be that there is quite a bit of room for future price reductions in the form of a Mac Pro with a new case design and simpler memory architecture.
Macbook Pro 1.83 (15")   Mac OS X (10.4.7)  
Macbook Pro 1.83 (15")   Mac OS X (10.4.6)  

Answer 1

For post-production and audio work, having a quieter computer is one of the reasons I ordered a Mac Pro - quieter is good. And as my MDD dual 867Mhz is now as long in the tooth as I am, it couldn't come at a better time. I was really contemplating buying a quad G5 the past 6 months, but then heard the professional desktop would come out during the developer's conference, and I'm glad I waited. The price is absolutely - and insanely - great. Mine should be here on the 15th, and I'll be counting the hours. As for the risers, I'm willing to endure a few nanoseconds as a trade-off.
Regards,
Rube
G4 867x2 2Gb   Mac OS X (10.4.7)