Inside the Macintosh 512K

Introduction

Following the release of the original Macintosh in 1984, Apple released the Macintosh 512K in 1985. The main difference between the two was the increase in RAM to 512 kB. The original Macintosh had 128 kB and started to be called the 128K after plans to release the 512K were revealed.

Just like the original Macintosh, the Macintosh 512K came originally with a 3.5” 400 kB floppy disk drive (at the time, most computers used 5.25” 360 kB floppy disk drives) and a 9-inch black-and-white video monitor with a resolution of 512 x 342 integrated on the computer’s body. The 512K was based on the Motorola 68000 microprocessor, which was one of the most powerful CPUs available at the time.

An upgrade version of the 512K with an 800 kB floppy disk drive was released in April 1986 and was called the 512Ke (for “Enhanced”). This model had the part number “M0001E”.

At the end of the Macintosh 512K’s life, Apple cut its price and renamed it to Macintosh ED, and targeted it to the educational market. This model had the part number “M0001D” or “M0001ED.”

The computer didn’t come with a hard drive, so the operating system and programs must have been loaded through floppy disks. All of the time we see people listing old Macs on eBay, saying that it is “defective” because the operating system is not loading and the computer is showing an icon with a floppy disk and a question mark. (The person selling the computer does not realize that old computers didn’t come with a hard drive.) This is the normal behavior of the computer when it doesn’t find a floppy containing the operating system, and it means the computer is working as expected.

The Macintosh 512K kept the same yellow color as the Macintosh 128K and the Apple IIe.

Figure 1: The Macintosh 512K

Nowadays, the first thing you will notice looking at the Macintosh 512K is how small it was. In Figure 2 we compare it to a 21-inch LCD monitor.

Figure 2: The Macintosh 512K compared to a 21-inch LCD monitor

Differently from the Apple II and Apple III, the keyboard was not part of the body of the computer. It was connected to the computer using a spiraled cable similar to the ones used by telephones. The keyboard was mechanical and almost identical to the one used with the Apple IIe, except that the old Open Apple and Solid Apple keys were replaced by the Command and the Option keys, respectively. This keyboard was identical to the one used with the Macintosh 128K. Later, Apple released a version of the 512Ke with the same keyboard that came with the Macintosh Plus, dubbed the 512Ke/800. This model had the part number “M0001D.”

Figure 3: The keyboard

The mouse was rectangular with a single button. To this day, Apple mice still have only one button. It was connected to the computer through a DE-9 connector identical to the one used on the Macintosh’s serial ports, but the mouse port used a proprietary format.

Figure 4: The mouse