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Will Intel Macs run Windows? - Part 1
The answer is No. And Yes. And It Doesn't Really Matter. Read on to find why.

Part 1: No - Why the new Macs can't run Windows.

When this question first appeared six months ago, the question was simply, "how similar will the new Macs be to today's PCs"? Apple was pretty secretive about the answers prior to MacWorld. Even now, there are still some missing details, but here's what we do know about Intel Macs vs. standard PCs, and why it matters.

The base hardware
Intel Macs are not only using Intel's Core Duo processor, but also a standard Intel logic board chipset. This itself would suggest that running Windows wouldn't be too difficult. However, there are complications that raise problems for booting Windows in the new Mac's firmware, additional installed hardware, and its disk partitioning.

The firmware
Firmware is low level code that is burned into the hardware. Macs originally had custom firmware ROMs, and later moved to OpenFirmware, an open specification created by Sun. In general, firmware controls the hardware for a few seconds from the initial power-on until the machine is ready to boot an operating system.

Firmware scans thorough the installed hardware, runs diagnostic tests, complies a list of devices, determines the operating system to be started, hands it the hardware list, and then assigns control of the hardware to that operating system. Once the OS begins booting, the role of the firmware is over.

The new Macs use Intel's new EFI firmware specification, rather than the OpenFirmware in current PowerPC Macs, or the BIOS used standard PCs. EFI shares a lot in common with OpenFirmware. Essentially, Intel wanted to offer OpenFirmware type features on its own hardware, but differences in x86 design and the existing implementations of OpenFirmware meant that Intel was better suited to creating a custom standard (EFI) that worked like OpenFirmware.

Actually adopting and modifying OpenFirmware to work with Intel's logic boards and processors would have introduced so many changes that no interoperability would have been possible anyway.

Intel's EFI isn't even very new. I considered writing another article: "A brief history of EFI" to fill in the details of why today's PC's don't yet use EFI, despite it being a huge leap beyond the archaic BIOS currently in use. However, the simple fact is that PCs don't use EFI.

Logically, Microsoft hasn't written firmware support for EFI PCs, because none exist. Windows currently can't boot using EFI. This is not a difficult technical problem to solve, but it does prevent installing Windows XP on a new iMac, or booting Windows from an already installed drive. Similarly, any Linux CDs designed to boot up on PCs won't work on the new Macs either.

The rumor mill came up with a possible loophole, after reading about Intel's specification for a BIOS compatibility mode running on EFI. But the new Macs have no need to provide legacy support for BIOS.

Further, Apple does have existing Mac features to support in firmware, and built these into the EFI on the new Macs; Firewire Target Disk Mode, Netboot, and the Startup Manager (option-boot) are all features Apple had to include in the new Macs. This makes it obvious that Apple's EFI implementation is not some generic standard version, but customized to suit Apple's existing base.

It was also suggested that Microsoft's 64 bit Windows for Itanium does support EFI, so perhaps that version would boot on the new Macs. However, Itanium is an entirely different processor architecture from x86 family (which includes the Core Duo).

Nobody would suggest that Sun SPARC servers should be able to boot Mac OS X, simply because Solaris supports OpenBoot (Sun's twin of OpenFirmware). Both the base hardware and firmware have to match! The new Mac's EFI firmware is currently strike one against booting Windows on a new Mac.

Continued: Additional hardware


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