Background Story:
In preparation for my move to San Francisco, I’ve had to start selling some of my excess computers, because I can’t justify bringing 9 desktop PCs to a city where a studio apartment will be between 400 and 500 square feet. Since I have four GX-270s, I sold the 2.8ghz GX-270 that I had been using to run OS-X. I took out the OS-X harddrive, installed Windows XP Pro (a legal copy – the new owner has his own legal license key for the OS), and sold the machine. Why? Because I figured that I could put the OS-X harddrive in one of my other GX-270s without any problems.

Being a computer tech, I should have known to test my theory first. After completing the sale, I returned home, put the OS-X harddrive in my 3.0ghx GX-270 and viola! It failed to boot. By failed to boot, I mean it resets the machine. So, I ventured over to a friends house (he has a 2.8ghz GX-270 and a 3.0ghz GX-270) to test OS-X. The 2.8ghz machine ran OS-X fine, but the 3.0ghz machine failed.

Experiment:
In an attempt to discover why the GX-270s with 2.8ghz Prescott chips have no problem with OS-X, and why the GX-270s with 3.0ghz Northwood chips won’t boot OS-X (from either a harddrive with OS-X already installed or from any of the available installers) I performed the following test:

Prescott 2.8ghz machines use the Dell Computer Corp 0Y1057 motherboard.
Northwood 3.0ghz machines use the Dell Computer Corp 0DG284 motherboard.

If you’d like to compare specific information between the processors you can check out the side-by-side Northwood v Prescott screenshots.

Machine #1 – Prescott – 2.8ghz
Step 1.) Booted the machine with its normal XP harddrive. Viola. No problems.
Step 2.) Swapped the harddrive with the OS-X harddrive. Machine booted without problems.
Step 3.) Tested the Kalyway 10.5.1 and 10.5.2 install DVDs. Machine had no problems with either.

Machine #2 – Northwood – 3.0ghz
Step 1.) Booted the machine with its normal XP harddrive. Viola. No problems.
Step 2.) Swapped the harddrive with the OS-X harddrive. Machine failed to boot.
Step 3.) Test the Kalyway 10.5.1 and 10.5.2 install DVDs as well as the Leo4All, Leo4Allv2, and Jas. All DVDs and the harddrive failed to boot the installation or OS. By fail, I mean the Darwin Bootloader comes up, but when the installer is launched the following text appears on the screen followed by an immediate reset of the machine:

“Using SMBIOS table found at 0×0 (hex value here)
Using ACPI RSDP revision 0 found
Starting Darwin/x86″

I believe my experiments this weekend show, that though both motherboards use the same chipset and southbridge…

The 0Y1057 (Dell’s motherboards for the Prescott) have the following LPCIO: “SMSC EMC2700P”
The 0DG284 (Dell’s motherboards for the Northwood) have the following LPCIO: “”

In the end there are two differences:

The LPCIOs are different.
The Prescott chips support MMX, SSE, SSE2, and SSE3.
The Northwood chips support MMX, SSE, SSE2, but not SSE3.

However, I’ve found instance on the forums of people with OS-X running fine on either chip. The Prescott supports MMX, SSE, SSE2, and SSE3, whereas the Northwood supports MMX, SSE, SSE2, and NOT SSE3. In theory this should not make a difference because the OSx86 projects should work on any chip that supports SSE2 or SSE3 (both do not have to be supported). That leaves the culprit to the LPCIOs.

Bottom line:
GX-270s with Northwood chips and the 0DG284 motherboard cannot run OS-X. This is after overall testing on two Prescott machines and five Northwood machines.

To make sure this is the actual case, I’ve ordered a Prescott chip (which should arrive in the next few days) to test in the 0DG284 motherboard. I’ll post the results once the new chip arrives.

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