Does the Mac mini G4 have a PCI slot?

No. The Mac mini is designed to be simple, small, and inexpensive, and consequently, there is no internal expansion other than AirPort Extreme and Bluetooth 1.1 (Bluetooth 2.0+EDR in the Mac mini G4/1.5).

If PCI slots are a high-priority, one would be better served by a model in the Power Macintosh G4, Power Macintosh G5, or Mac Pro series.

What are the capabilities of the optical drive provided by the Mac mini G4? Can one upgrade the optical drive?

All Mac mini G4 models have an optical drive that is at least capable of reading DVD-ROM and writing CD-R and CD-RW.

The specific capabilities are provided on the specs page for the particular model of interest. However, for your convenience, this information also is provided below:

Mac mini G4	Part Numbers	Optical Drive
Mac mini G4/1.25	M9686LL/A & /B	8X "Combo"
Mac mini G4/1.42	M9687LL/A & /B	8X "Combo"
	M9971LL/B	4X "SuperDrive"
Mac mini G4/1.5	M9687LL/B†	8X "Combo"
	M9971LL/B†	8X DL Read "SuperDrive"

†Unfortunately, Apple did not release new part numbers for the "stealth" update Mac mini G4/1.5.

Apple does not recommend that individuals attempt to upgrade the Mac mini G4 optical drive or other internal components themselves. Consequently, EveryMac.com does not advise self-installation contrary to Apple's recommendation.

However, site sponsor Other World Computing provides an excellent video instruction guide covering replacement of the optical drive.

Site sponsor Other World Computing sells RAM, hard drives, and optical drives that are compatible with the Mac mini G4. If you do not feel comfortable upgrading the Mac mini G4 yourself, the company also offers an inexpensive and convenient "upgrade by mail" service.

Does the Mac mini G4 have an external power supply? How large is it?

Yes. The Mac mini G4 has an external power "brick" that is approximately six inches by two inches by two inches. Although it is rather large, it is smaller than the external power supply used by the long ago discontinued Power Macintosh G4 Cube models.

Can Mac mini G4 systems be stacked on top of one another?

No. Apple recommends against stacking multiple Mac mini systems on top of one another because this can restrict airflow and reduce the signal strength of AirPort Extreme and Bluetooth (if installed). However, Apple says that it is okay to place a Mac mini on it side.

For more information on appropriate positioning of the Mac mini, please refer to "How to Position Your Mac mini" from the Apple Support Site.