Apple's release last week of an update to the G5 line includes a switch from dual processor to dual core and also what Apple calls the "Power Mac G5 Quad". The G5 Quad they make reference to is actually two dual core chips and not four separate procs. In line with this, each dual core processor has its own bidirectional frontside bus. What this means is data transfers between the frontside bus and each dual core proc has half the throughput of a dual processor system. AMD in contrast using their hypertransport technology can communicate directly between the two parts of the dual core.

More techie stuff after the jump.

A positive point for the G5 Quad is that they do include four separate 1Mb L2 caches. Also, the G5 Quad can perform both a multiply and add in each floating point calculation. If your software has been optimized for a G5 Quad, this can lead to up to 16 64 bit floating point operations per second because each core has two floating point units.

As pointed out by other people writing on dual core versus dual processor technology, the same speed dual core can be slower as well as more expensive than its dual processor counterpart. In the case of the G5 Quad and the two other dual core G5's released this week, the speed boost may end up being a speed cut.

Perhaps before buying a G5 Quad you may want to ask yourself a few questions:
1. Are you involved in high intensity computing? (science, post-production video/audio, 3D rendering)
2. Do you have code that is already optimized for the PowerPC architecture?
3. Have you set the tech specs of the G5 Quad as your desktop background?

If you answered yes to question one:
You probably already have a strapped budget and are making do with split shifts across night hours. If not, you may already have a super computer or cluster set up at your facility.

If you answered yes to question two:
Your PowerPC code may have to be re-optimized for multithreading to take advantage of multi proc machines.

If you answered yes to question three:
You may be ill. Gear lust is a treatable condition.

If you answered yes to all three I'd say you might want to consider purchasing the G5 Quad for your facility. If not, remember that upping the RAM in your existing system can be a lot cheaper and less time consuming an upgrade!