Apple introduced the PowerBook Duo 2300c/100 on August 28, 1995 and began shipping units by October 1995. The PowerBook 2300 is the last of the Duo line. PowerBook Duos are subnotebooks that have almost no ports and no internal floppy disk drive. Duos must use a dock like a MiniDock or Duo Dock in order to expand capabilities and give them access to standard Macintosh and PowerBook ports. The PowerBook Duo 2300 originally cost $3500 to $4500 depending on the configuration. We acquired our PowerBook Duo 2300 in 2008 for $30.

The PowerBook Duo is the only Duo to use a PowerPC processor. The 2300 has a 100 MHz PowerPC 603e processor. The PowerBook 2300 series replaced the Duo 200 series, which were 680x0-based.

The 2300 has 8 MB of built-in RAM and one RAM slot that uses 70 ns Duo RAM. It can address up to 56 MB RAM. Our 2300 has 24 MB RAM. The 2300 originally shipped with Mac OS 7.5.2 and it supports up to Mac OS 9. It is advisable to have the full 56 MB of RAM if you intend to use Mac OS 8.6 or Mac OS 9. Mac OS 8.5 requires at least 32 MB. 16 to 20 MB is recommended for Mac OS 7.5 to Mac OS 7.6. Our 2300 is currently using Mac OS 7.5.5.

Apple offered either a 1.1 GB or 750 MB internal IDE hard drive. Our 2300 has a 750 MB hard drive. Duos like the 2300 do not have a built-in floppy disk drive and have few ports. Connectivity and expansion requires the use of a docking device or adapter. The 2300 does have a single expansion slot for an internal modem (RJ-11). Our 2300 does not have a modem card installed.

The Duo 2300 has few built-in ports. The only standard ports on the Duo 2300 are one optional internal modem port (RJ-11) and a serial port (RS-422) for a printer or external modem. The Duo 2300 has a built-in omnidirectional microphone located above the keyboard. The 2300 also has a tiny built-in speaker residing in the monitor casing.

The largest port on the Duo 2300 is a 152-pin Processor Direct Slot (PDS) located on the back. The slot is used to plug the Duo 2300 into a dock that provides additional connectivity. Apple sold two primary types of docks: a MiniDock and a full-sized Duo Dock desktop system. Apple also sold a Duo Floppy Adapter, which allows for the connection of an external HDI-20 floppy disk drive and an ADB keyboard and mouse.

The MiniDock adds a variety of ports, including: one HDI-20 floppy drive port, one HDI-30 SCSI port, one DB-15 monitor port, one serial external modem port, one serial printer port, one sound-in jack, one sound-out jack, one ADB port, and one modem port (RJ-11).

The Duo Dock has most of the same ports as the MiniDock (the Duo Dock does not have an HDI-20 port), but it includes a PowerLatch slider mechanism that pulls the PowerBook Duo inside the chassis, similar to a VHS tape being pulled into a VCR (Video Cassette Recorder). The Duo 2300 is fully compatible with the Duo Dock Plus. It is not compatible with the original Duo Dock because the compartment that holds the subnotebook is too narrow, designed for use with earlier Duos that have grayscale displays. The Duo Dock II has a larger compartment to accommodate Duos with color displays, but the PowerBook 2300 cannot utilize the Dock II's built-in FPU and 32K level 2 cache, which are not compatible with PowerPC processors.

The Duo Dock turns the PowerBook Duo 2300 into a full desktop system. Other than the array of ports it adds to the subnotebook, it also offers additional video RAM (VRAM), a built-in floppy disk drive, two NuBus expansion slots, and room for an optional internal hard drive. An external monitor is required because the PowerBook Duo 2300 has to be folded up and inserted into the Duo Dock Plus in order to make the connection.

The 2300 has a larger built-in display than the previous Duos. It has a 9.5-inch (versus 8.4-inch) color active-matrix LCD. It is capable of 16-bit color depth (thousands of colors) at 640 x 400 and 8-bit color depth (256 colors) at 640 x 480. The brightness of the display is controlled by two buttons located over the speaker grill on the right side of the display. When attached to the Duo Dock Plus, the resolution of the display and its color depth depends partially on the external monitor being used. The Duo Dock Plus has 1 MB of built-in VRAM.

Unlike the previous Duos, the Duo 2300 uses a trackpad instead of a trackball for cursor control. The trackpad lets you double-click by tapping twice -- no need to switch to the button like on the trackball Duos. You can even drag-lock by doing one-and-a-half taps (down, up, and back down). And you can drag an item, lift your finger briefly off the touch pad, put it down again, and resume dragging. It is almost as intuitive as finger painting.

The Duo 2300 shipped with the Duo Nickel Metal Hydride (NiMH) Type III battery that is capable of two to four hours of continuous use on a single charge. Apple produced three types of Duo batteries: Type I, II, and III. Type I batteries came installed in Duo 210 and 230 systems, Type II batteries came installed in Duo 250, 270c, and 280 systems, and Type III batteries were installed in the Duo 280c and 2300. It is possible to use both Type II and Type III batteries in Duo 210 and 230 systems with the addition of appropriate battery management software. Type I batteries can be used in newer Duo systems, but battery life is significantly reduced. The PowerBook 2300 series uses the same power adapter as the 200 series Duos.

Apple originally sold the PowerBook 2300 in two price configurations:

• $3500, 8 MB RAM, 750 MB IDE hard drive
  
  
• $4500, 20 MB RAM, 1.1 GB IDE hard drive

Apple began to deemphasize the Duo name with the release of the Duo 2300, calling this subnotebook series simply PowerBook 2300 series, although the Duo name was clearly stenciled on its case. The 2300 series retained the advantages of the earlier Duos: light weight (4.8 pound), and docking options. The 2300 series also retained the disadvantages, such as the need to add expensive components like floppy drives and docking stations for them to function like desktop Macs.

At the introduction of the 2300 series, rumors of the demise of the Duo line with the realization that the 2300 would be the last Duo were common. But Apple didn't simply let the subnotebook concept die with the Duo line. The PowerBook 2300 series was discontinued on February 1, 1997, just in time for the introduction of the PowerBook 2400 series a few months later. The 2400 series was a subnotebook in all aspects, but it didn't require the need for a docking device and came arrayed with a multitude of built-in ports. The popular PowerBook 2400 series was the clear successor to the Duo line. Apple's Duo concept had run out of steam with the PowerBook Duo 2300, but Apple was able to successfully transform the Duo line from a stripped down (almost crippled) subnotebook needing docking devices or adapters into the PowerBook 2400, a mini-laptop or fully functioning subnotebook with most of the capabilities and built-in ports of full-sized PowerBooks.