Apple introduced the PowerBook 145B on June 7, 1993 as a replacement for the PowerBook 145. The PowerBook 145B offers the same performance as the 145, but at a lower price and with 2 MB more RAM soldiered to the motherboard. The PowerBook 145B originally cost between $1550 and $2350 depending on options. I purchased my PowerBook 145B in 2008 for $40.

The PowerBook 145B uses the same processor as its predecessor, a 25 MHz 68030 processor with no FPU for floating point calculations. The 145B has 4 MB RAM soldiered to the motherboard and can accept up to 4 MB more PB1xx RAM in its single RAM slot giving the 145B a total possible RAM of 8 MB. My PowerBook 145B only has the 4 MB built-in RAM. My PowerBook 145B uses Connectix RAM Doubler, which tricks the system into thinking that total available RAM is 8 MB as shown in the "About This Macintosh" screen capture below. RAM Doubler compresses RAM right in memory to store up to twice as much information in RAM, and if necessary, RAM Doubler will briefly use the hard drive to store memory similar to but much faster than System 7 Virtual Memory.

The PowerBook 145B originally shipped with Mac OS System 7.1 and it officially supports up to 7.6.1. Given the RAM ceiling of only 8 MB, it is not advisable to install more than System 7.1, especially if your 145B only has its 4 MB of onboard RAM. Older Macs with 4 MB or less RAM cannot effectively run System 7.5 because it takes up nearly all available system RAM just to run the operating system. My 145B uses System 7.1 and has never been upgraded past its original OS.

The 145B uses the same monitor as the 145. The 9.8-inch monitor displays only black and white (1-bit) and is capable of a single resolution of 640 x 400. It is passive-matrix and thus has a washed out look if not viewed straight on. Two slider knobs residing over the right hand side of the keyboard just below the monitor control contrast and brightness. The 145B does not have video out to support an external monitor.

The PowerBook 145B shipped with either an 80 MB or 120 MB internal SCSI hard drive. My PowerBook 145B has an 80 MB internal hard drive. The 145B has a single built-in 1.4 MB internal floppy disk drive. The PowerBook 145B has the following ports: one ADB port, one HDI-30 SCSI port, one serial printer port, one serial modem port, one microphone jack, and one speaker jack. The PowerBook 145B also has an optional RJ-11 modem port. The modem slot is the PowerBook 145B's only expansion slot. My PowerBook 145B has a 14.4K modem card installed in this slot. The 145B does not have an internal microphone. The ports are housed on the back of the laptop under a plastic port cover. The power button, reset button, and interrupt button are also located under the port cover.

The PowerBook 145B uses the same NiCd battery and power adapter as all the classic chassis PowerBooks. A good battery is capable of between 2 to 3 hours of continuous use. The 145B inherited the sleep feature first introduced with the PowerBook 145, which allows the user to program through a Control Panel the 145B to sleep or completely shut down whenever the clamshell unit is closed.

The PowerBook 145B was replaced by the PowerBook 150 on July 18, 1994. Although the PowerBook 150 has a better monitor and a faster processor, it lacks many of the 145B's ports. The 150 has a slightly smaller monitor that is capable of grayscale, but like the 145B, it is passive-matrix. The 150 originally cost less than the 145B and it shipped with either a 120 or 250 MB internal IDE hard drive. The 150 has a greater maximum RAM capacity of up to 40 MB, but like the 145B, it has 4 MB onboard RAM. However, the 150 uses faster 70 ns Duo RAM in its single RAM expansion slot.

The 145B was the lowest cost PowerBook of its day. It replaced the 145, which itself replaced the PowerBook 140. But unlike the 140, which was considered a mid-range PowerBook at the time of its introduction, the 145 actually took over the PowerBook 100's entry-level position in the PowerBook lineup. The 145 and 145B share the same form factor as the PowerBook 140. Thus the 145 is essentially an upgraded version of the 140 and the 145B is essentially an upgraded version of the 145.