May 28, 2025 14:00:00

Why did the original Mac have a resolution of 512 x 342 pixels instead of 512 x 384 pixels?

The first model of Apple's Macintosh series, the '

Macintosh 128K ', was equipped with a 512 x 342 pixel display. Stephen Hackett , an Apple product enthusiast, speculates on why the half-baked '512 x 342 pixel' display was adopted instead of the '512 x 384 pixel' with an aspect ratio of 4:3.

Why the Original Macintosh Had a Screen Resolution of 512x342, and not 512x384 as One Might Expect - 512 Pixels
https://512pixels.net/2025/05/original-macintosh-resolution/

The Macintosh 128K is a personal computer released by Apple in 1984. It was sold at a relatively low price of $2,495 (about 360,000 yen) while being equipped with a large capacity of 128KB memory at the time and an intuitive UI that could be operated with a mouse. Below is a photo of the Macintosh 128K and Steve Jobs together.

The Macintosh 128K was equipped with a black-and-white display of 512 x 342 pixels. The later Macintosh series was equipped with a display with an aspect ratio of 4:3 of 512 x 384 pixels, but for some reason the Macintosh 128K was equipped with a display with an aspect ratio of half-hearted. Hackett considered the reason why the Macintosh 128K's display resolution was 512 x 342 pixels based on 'memory' and 'CPU'.

Memory

Andy Hertzfeld , a member of the Macintosh development team, said, 'The original Macintosh had only 128KB of memory, and memory management was the most difficult part of both system and application development. We allocated about 16KB for the system and another 22KB for the 512 x 342 pixel black and white display, which left only about 90KB of memory for applications. Large applications like MacWrite and MacPaint were at their limit.' From this, it can be said that the memory of the Macintosh 128K is at its limit, and if a display with a higher pixel count is adopted, the amount of memory required for screen display will increase and there will not be enough memory to allocate to applications.

In addition, a post on the social news site Hacker News suggested that 'memory bandwidth, rather than memory capacity, may have also been a factor in determining display resolution.'

◆CPU
The Macintosh 128K's CPU was the Motorola 68000 , with a clock speed of about 7.83MHz. The Macintosh 128K's display had a vertical refresh rate of 60Hz, and many of the Motorola 68000's resources were allocated to screen drawing. If the display resolution was changed from 512x342 pixels to 512x384 pixels, the CPU resources allocated to screen drawing would increase, and there would be less room for applications to run.

The display on the

Lisa personal computer released by Apple in 1983 had a feature in which each pixel was a vertical rectangle. The Lisa development team was working on changing the pixel shape to a square, but due to shipping schedule restrictions, the pixel shape was left rectangular. The Macintosh 128K, which appeared the year after the Lisa, succeeded in making the pixels square.