Editor's note: This article is the first in a series as we sort out this information which has come to us from a very informed engineer-reader. What's inside constitutes an "educated guess" (nothing more unless by coincidence) and discusses the very technologies Apple likely has incorporated into its Rack Mount Server product. We will publish more shortly.

Over the last several days Architosh has had the interesting privilage of sharing information with a particular individual named Douglas Godfrey, who says he has no inside information from Apple or Motorola but has come up with possible specifications for a 4-6 way Apple server which could feature a combination of G4 and G5 processors.

The Motorola MPC8540

The Motorola PowerPC 8540 has been regarded on this site as a candidate for the G5 chip, if it was adapted to include support for AltiVec and AGP. However the current MPC8540 apparently does not include these capabilities, according to our friend Godfrey.

As Godfrey reminds us, the MPC8540 is "aimed at the broadest part of the embedded CPU market." This includes edge routers, web servers, SetTop boxes and Web appliances. For most of these markets AltiVec offers no real benefit, "instead, minimum possible power consumption per MIPS and multiple Ethernet/Serial Ports are needed."

The True G5

As Godfrey suggested, Motorola will not have a "true G5" based chip until late 2002 or early 2003. (Ed's. Note: It is our current sentiment that Apple may beat this speculation with a true G5 part for Macworld Expo New York 2002, and tomorrow's server announcement will either confirm this or change it). Motorola's "true G5" chip is designed to accommodate not only Apple Computer but a whole range of customers in need of an embedded chip with AltiVec support. As Godfrey notes, this would include core routers, DSPs, Printer Controllers, et cetera.

When Motorola announces a MPC 8xxx chip with AltiVec support, it should be no later than six months before they (Apple) are shipping Power Macs G5's.

Godfrey's Rack Mount Apple Server with 6 Processors

Douglas Godfrey believes that everything that is needed to build a 6-way multiprocessor Mac server is available today and that Apple tomorrow will introduce a system that looks very much like this:

The New G5 Server: Godfrey's Guess

• 4 - MPC PPC 8540 CPU's at 1GHz (that's 4 G5's folks)
• 2 - MPC PPC 7455 CPU's at 1 GHz (that's 2 G4 Apollo chips)
• 1 - Tundra Tsi500: RapidIO 6 Port Switch
• 2 - Tundra Tsi890: PowerPC Universal Interconnect Switch (Northbridge)
• 2 - TI 1394b OHCI controllers (64bit 66mhz PCI)
• 2 - KeyLargo ASIC's (Southbridge, USB, IDE, ATI/100)
• 1- PMU99 Power Management Controller

The system above would have:

• 13,000 MIPS for PowerPC Server Applications
• 6 - PCI-X - PCI 64/66 Controllers (up to 24 PCI slots)
• 6 - DDR 333mhz Memory Controllers (up to 16 Gigabytes/sec I/O)
• 12 - Gigabit Ethernet Ports (built-in Gigabit Hub/Router)
• 12 - Serial Ports
• 24 - DMA Controllers
• 4 - USB 1.0 ports
• 6 - 1394b 800Mbps FireWire ports (FireWire Raid 0/1/5/5+Hotswap)
• 2 - IDE/ATAPA ports
• 2 - IDE/Ultra ATA 100 ports (IDE Raid 0/1)

How Does a G4 and G5 Work Together?

Whether or not Apple releases a G5/G4 combo or just a 4-way G5 Server, one question that came up in our discussions with Godfrey was "how does a G4 and G5 work together in the same machine?"

The answer is, apparently "the Mach kernel that is a part of Darwin already has support for dispatching tasks to CPU's that have different capabilities (Ed's. note: we welcome your comments here) and the Apple HFS+ file format already includes flags to indicate AltiVec Aware versus AltiVec Required".

In such a system a couple of G4 chips would run the interface and any AltiVec dependent code and the other G5 MPC8540 chips would do the bulk of the code crunching. The bulk of the Darwin kernel is non-AltiVec. The MPC8540 is equivalent to the MPC7455 plus the Tundra Tsi890. However, the memory system in the MPC8540 is faster than the current G4 (MPC7455) because the memory system is "embedded into the MPC8540 and has access to a 6 Gigabyte/sec 'crossbar switch' that is the core of the MPC8540".

This is why--it is important to note--that the MPC8540 with 256k L2 and no L3 cache has a higher MIPS rating than that of the MPC7455 G4 with 1 BM of L3 cache.

Closing Comments

There is little doubt here that Douglas Godfrey is an engineer who understands the technologies behind what it would take to put together a powerful server machine. However, as he points out, all of the information supplied here is open information. He tells us that he is not an Apple employee (though he would like to be one) but does believe that Apple has a similar system planned for its May 14th release.

If you would like to learn more, revisit this page for updates and further links.

Related Articles

Apple Server: Specs on Render Farm, Sci/Tech Server