Feature

Thinking different

With the Mac Mini, Apple squeezes substantial computing horsepower into a diminutive form factor

By Brian Dipert, Senior Technical Editor -- EDN, 12/16/2005

Three months ago, I covered how the Mac mini stacked up, in terms of performance, against past and present members of Apple's various computer-product families. At that time, I wasn't able to also show you how the company contorted the computer's design until it fit into a fetching, infinitesimal 6.5×6.5×2-in., sub-three-pound form factor (Figure 1), but I promised that my dissertation of that dissection would soon grace the pages of EDN. Well, here it is. I'd like to thank the folks at Other World Computing for the high-quality images that accompany this write-up.

Read more Prying Eyes

After you take a putty knife to the Mac mini in order to remove its top housing (see "Cracking open the case"), you'll be staring at the system's optical drive (Figure 2). For orientation purposes, keep in mind that the bottom of Figure 2 correlates to the front of the system. My Mac mini comes with a Matsushita/Panasonic UJ-835F SuperDrive which both plays and burns DVDs (as well as CDs); lower-priced system variants contain "Combo Drives," which are capable of reading, but not writing, DVDs but read and write CDs. 

The rectangular antennas for the Mac mini's Bluetooth/Wi-Fi wireless module, which is optional in some product variants and standard in others, clip to the internal frame at the top of the unit. The Bluetooth antenna is at the front of the system (the bottom left corner of Figure 2), while the Wi-Fi antenna is in the back (top right corner). Along the left side you can just barely see the single-slot PC7200 (DDR-266) DRAM module. Its location will be clearer in subsequent images. My system came with a 256-Mbyte memory module comprised of Hynix DRAM. I later upgraded it to a 512-Mbyte module in order to improve overall system performance.

Inspecting the internal frame

By taking out three screws and lifting the internal frame straight up, thereby unplugging it from a connector located on the main system board, you can remove the internal frame from the rest of the Mac mini (you may also need to route the antennas and their cables, if they're present, through the opening in the frame). Figure 3 shows the underside of the internal frame, including the 2.5-in. hard-disk drive. My system came with a 40-Gbyte Seagate Momentus drive; although the system specs a 4200-rpm drive, mine had a 5400-rpm version. I later upgraded to a 100-Gbyte Momentus drive, among other reasons because I occasionally use the Mac mini as an HDTV PVR in conjunction with an Elgato EyeTV 500 Firewire-based receiver.

Figure 3 is left-to-right reversed with respect to the way the internal frame is positioned when installed in the system, but the top-to-bottom orientation is preserved (top equals back and bottom equals front, as before). In the top right corner you'll see the male connector that electrically mates the internal frame to the system board. In the bottom left corner is the system fan, which you need to remove (two screws) in order to swap out the hard-disk drive. Note that it is mechanically possible to install the drive upside-down. I confess I found this out from personal experience. Fortunately, this mistake didn't destroy the drive. When neither the hard-disk drive nor optical drive functioned, I quickly figured out what I'd done, and correctly orienting the drive restored normal system function.

The system airflow is, to me, the most interesting aspect of Figure 3. Peek ahead to Figure 4 and you'll discover that the large hole in the top left corner of the internal frame's underside is just big enough for the passive heat sink on the system board to fit inside it. Air enters the system through a series of vents at the periphery of the Mac mini's underside. It flows through the fan, then over the heat sink, and finally exits the system through a vent at the back of the unit.

Examining the mezzanine board

Figure 4 shows the system board—well, most of it. For now, focus your attention on the bottom left corner, which, thanks to the two thick wires emerging from it, you might have already guessed has something to do with the system's antennas. You'd be right.

Remove two screws, lift the mezzanine board straight up (disconnecting it from another connector on the system board) and you can flip it around and see what's underneath. The first-generation mezzanine board housed a standard Airport Express card, containing a Broadcom 802.11b/g transceiver. A separate sub-board, attached to the mezzanine board via two screws, contained a Cambridge Silicon Radio Bluetooth v1.1 transceiver. The Wi-Fi and Bluetooth antenna wires connect to the respective boards via male/female plug pairings. The second-generation, more compact mezzanine board design shown in Figure 5, according to my contacts at Other World Computing, has downsized the component count and integrated the Bluetooth and Wi-Fi functions.

Scrutinizing the system board

With the mezzanine board out of the way, you can more clearly inspect the Mac mini's motherboard (Figure 6). Along the left side is the DDR SDRAM DIMM connector, and the 512-Mbyte SRAM L2 cache from Hynix is in the bottom right corner (below it is the system configuration backup battery). The mezzanine board connector is in the bottom left corner, while the internal frame connector is on the left side of the board near the top. Above it, at the top edge of Figure 6, you can now clearly see the airflow exit vent, which corresponds to the back of the unit (where you'll also find two USB 2.0 connectors, a Firewire-400 connector, a DVI-I video port, a 10/100-Mbps Ethernet port, a modem port, a headphone jack, a power connector, and the on-off switch). And in-between the mezzanine and internal frame connectors there's a small connector for the analog-modem board, which isn't shown in this writeup's artwork (and which, depending on the product variant, is either included by default or is an add-in option).

Most of the action, though, lies underneath the passive heat sink. Visit the image gallery at www.123macmini.com/gallery and, among other things, you'll find the handiwork of souls brave enough to pry away the heat sink. I didn't have the stomach for potentially rendering this expensive piece of equipment defunct, so for now you'll have to take my word that underneath the heat sink you'll find the Freescale G4 PowerPC CPU, along with ATI Technologies' Radeon 9200 graphics processor and its corresponding 32 Mbytes of frame-buffer DRAM.

First-generation Mac minis came in 1.25-GHz (mine) and 1.42-GHz PowerPC flavors. Recent units reportedly are shipping in 1.33-GHz and 1.5-GHz versions (along with bumping up the graphics memory to 64 Mbytes), although to date Apple has made no formal announcement of an upgrade. Visit www.123macmini.com/gallery and you'll also be able to see what's on the underside of the Mac mini's motherboard.

Author information

You can reach Senior Technical Editor Brian Dipert at 1-916-760-0159, bdipert@edn.com, and www.bdipert.com.

 

For more information
Apple Computer www.apple.com	ATI Technologies www.ati.com	Broadcom www.broadcom.com
Cambridge Silicon Radio www.csr.com	Elgato Systems www.elgato.com	Freescale www.freescale.com
Hynix www.hynix.com	Matsushita/Panasonic www.panasonic.com	Other World Computing www.otherworldcomputing.com
Seagate www.seagate.com