Apple introduced the PowerBook Duo 230 on October 19, 1992 along with the PowerBook Duo 210. The PowerBook Duo is a subnotebook that has almost no ports and no internal floppy disk drive. It must use a dock like a MiniDock or Duo Dock in order to expand its capabilities and give it access to standard Macintosh and PowerBook ports. The PowerBook Duo 230 originally cost $2610. We acquired our PowerBook Duo 230 in 2008 for $25.
The PowerBook Duo 230 packs tremendous computing power in a package just 1.4 inches thick. It features a 33 MHz 68030 microprocessor. The Duo 230 does not have a built-in FPU, but one can be added in the Duo Dock. By eliminating the internal floppy drive along with other size and weight saving measures, Apple got the weight down to just 4.2 pounds.
The only standard ports on the Duo 230 are one optional internal modem port (RJ-11) and a serial port (RS-422) for a printer or external modem. Apple provided an optional Macintosh PowerBook Express Modem capable of 14,400 bit per second (bps) data with fax send and receive at 9600 bps. The Duo 230 has a built-in omnidirectional microphone located above the keyboard. The 230 also has a tiny built-in speaker residing in the monitor casing.
PowerBook Duo 230 ports
The largest port on the Duo 230 is a 152-pin Processor Direct Slot (PDS) located on the back. The slot is used to plug the Duo 230 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 PowerBook Duo 230 has a sturdy magnesium frame that provides enough rigidity to the case to ensure that the laptop and docking station align properly during docking. The Duo Dock turns the PowerBook Duo into a full desktop system. Other than the array of ports it adds to the subnotebook, it also offers additional video RAM (VRAM), two NuBus expansion slots, and an optional FPU (standard on the Duo Dock II). An external monitor is required because the PowerBook Duo has to be folded up and inserted into the Duo Dock in order to make the connection. Apple produced three Duo Docks: the original Duo Dock, the Duo Dock II, and the Duo Dock Plus. All three docks are compatible with the Duo 230.
PowerBook Duo 230 inserted into a Duo Dock Plus
The Duo 230 supports up to 24 MB RAM. It has 4 MB low-power DRAM soldered to the motherboard. The Duo 230 has one RAM slot that accepts 70 ns Macintosh PowerBook Duo RAM. Our Duo 230 has 18 MB of RAM.
The Duo 230 has a 9.1-inch bright backlit Supertwist LCD passive-matrix grayscale display, capable of generating 16 shades of gray at a single resolution of 640 x 400 (4-bit). Contrast and brightness for the built-in display is controlled by four buttons residing on the bottom right side of the display. The display can be significantly enhanced by inserting the Duo 230 into a Duo Dock, which has up to 1 MB of VRAM and the capability to display 16-bit color depth (thousands of colors). See the specifications for each of the three Duo Docks for a detailed listing of the resolutions possible. Duo Docks use an external monitor.
PowerBook Duo 230 LCD display
Like the other PowerBooks at the time, the Duo 230 uses a trackball for cursor control. The trackball used on the Duo 230 is about a quarter of the size of the large ball used on regular trackball PowerBooks. The Duo 230 has a built-in keyboard with standard Macintosh layout. When inserted into a Duo Dock, it is necessary to use an external ADB keyboard and mouse.
The Duo 230 shipped with the Duo Nickel Metal Hydride (NiMH) Type I battery. The battery can provide from two to four hours of 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 Duo 230 uses the Macintosh PowerBook Duo AC Adapter.
PowerBook Duo 230 battery
Apple offered either an 80 MB or 120 MB internal SCSI hard drive. Our Duo 230 has a 300 MB hard drive. The Duo 230 does not have a built-in internal floppy or CD drive. Connectivity with external drives has to be facilitated through a docking device.
The PowerBook Duo 230 originally shipped with Mac OS 7.1 and it is capable of supporting up to 7.6.1. Our 230 uses Mac OS 7.5.5. The two sets of desktop images below show our Duo 230 in a Duo Dock Plus using an external monitor and using its own built-in display. The Duo Dock Plus adds 1 MB VRAM and displays thousands of colors using the monitor hooked to the Dock. The 230's built-in LCD monitor can only display grayscale or black and white.
Images taken from Duo 230's internal display:
"About This Macintosh" showing system software and RAM
The Duo 230 was discontinued in July 1994. Apple would go on to sell PowerBook Duos for about three more years, finally ending in February 1997 with the termination of the PowerBook Duo 2300c. The Duo 230 was popular among Duo users, but the platform as a whole was never as popular as the regular line of PowerBooks. By 1997, miniaturization had begun to reach the point where consumers just couldn't justify buying a pricey dock to use with a pricey subnotebook that had almost no ports and no built-in floppy or CD drive of its own. The Duo Dock concept was unique to Apple Computer. It was an attempt to overcome the shortcomings of early laptops that offered portability but suffered from limited capabilities (connectivity, processing power, and video) in comparison to traditional desktop systems. The Duo line took advantage of advances in systems networking in order to free the laptop from the need to house media drives like a floppy disk drive or CD-ROM drive. This gave the Duos unmatched portability, but consumers for the most part just didn't get it. By in large, potential laptop consumers did not see the lack of an internal floppy disk drive or the need to use docking devices as an equal exchange for increased portability.
See Vectronic's Duo Dock Plus and PowerBook Duo 230 in action: