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The Sphere 1 Computer: A Closer Look at the Pioneering 1975 PC Case Design

When we think about the history of personal computers, names like Apple, IBM, and Microsoft usually come to mind. But there‘s an often-overlooked early PC that deserves a prominent place in the history books—the Sphere 1 computer. Released in 1975 by the Sphere Corporation of Bountiful, Utah, the Sphere 1 was one of the first complete, ready-to-use personal computers. And a big part of what made it so innovative was its compact, all-in-one case design.

At a time when most early PCs were sold as a collection of bare circuit boards that the user had to assemble and install into their own case, the Sphere 1 stood apart. It came fully assembled in its own integrated case, with a built-in keyboard, numeric keypad, and a 12-inch CRT monitor. This may not sound revolutionary today, but in 1975, it was extremely forward-thinking.

Inside the Sphere 1‘s Compact Case

The Sphere 1‘s metal case, measuring about 18 inches deep, 18 inches wide and 12 inches tall, was compact for the time. But it still managed to contain an impressive collection of full-size, cutting-edge components.

At the heart of the system was a Motorola 6800 microprocessor running at 1 MHz. The 6800 was one of the first widely available true 8-bit microprocessors and offered performance comparable to much larger and more expensive minicomputers of the era. It included a 16-bit address bus allowing it to directly address up to 64KB of memory. [1]

The base Sphere 1 system came with 4KB of RAM, expandable up to a maximum of 64KB. While 4KB may seem tiny by modern standards, it was actually quite generous for a personal computer in 1975. For comparison, the popular Altair 8800 hobby computer, released the same year, came standard with just 256 bytes of RAM! [2]

Also inside the Sphere 1‘s densely packed case was a 12-inch CRT monitor, which provided a full-size 24 line by 80 character display. Again, this was remarkable for 1975, when many early PCs like the KIM-1 and Altair 8800 didn‘t include a display at all. Those that did, like the MITS Altair 680, often used small calculator-style LED or gas discharge displays. [3]

Rounding out the Sphere 1‘s case were a full-stroke QWERTY keyboard, a separate numeric keypad, a front control panel with switches and blinkenlights, and even a cooling fan to keep all the tightly packed components from overheating. It was a true feat of 1970s industrial design to fit all of this into an 18-inch desktop case.

Expandability and Peripherals

Despite its small size, the Sphere 1 was surprisingly expandable thanks to its thoughtful case design. The back panel included a variety of interface ports for connecting peripherals:

  • Dual floppy disk drives (optional)
  • Up to 20MB of hard disk storage (optional)
  • Analog to digital converters
  • Printers (IBM Selectric, Teletype, etc.)
  • Paper tape reader
  • Additional terminals
  • Cassette tape interface

With the optional dual 8-inch floppy drives and 20MB hard disk, the Sphere 1 offered data storage capabilities far beyond most other personal computers of 1975. Its ability to interface with industrial peripherals like paper tape readers and analog sensors also made it suitable for business and scientific use, not just hobbyists. [1]

Internally, the Sphere 1 also had expansion slots for adding more memory, I/O interfaces, and other upgrades. This modular design approach was very advanced for the time and anticipated the expansion card slots that would become standard in later PCs.

The Sphere 1‘s Place in PC History

The Sphere 1 may not have been a huge commercial hit, with only around 1,300 units sold before Sphere Corporation went bankrupt in 1977. [4] But its influence on the young PC industry was significant.

Its pioneering all-in-one design with integrated display, keyboard, and case would be emulated by later PCs like the Commodore PET and TRS-80. And its relatively user-friendly, appliance-like design anticipated the direction the PC market would soon go in the late 1970s and early 1980s.

The Sphere 1 also helped popularize the 6800 microprocessor in personal computers, paving the way for the later success of 6800-family CPUs like the 6502 used in the Apple II, Atari 400/800, and Commodore PET. Its keyboard-controlled reset feature, while not unique, was also an early example of a user-friendly feature that would later become standard.

Admittedly, the Sphere 1‘s $860 price tag (equivalent to over $4000 today) was likely too high for the mass market. Its limited software library and lack of color graphics also put it at a disadvantage against the Apple II and other 1977 PCs in the nascent home computer market. [4]

But for its time, the Sphere 1 represented the cutting-edge of what was possible in a self-contained, easy-to-use personal computer. Its compact, well-designed case was a major milestone in PC industrial design and foreshadowed the sleek all-in-one PCs we take for granted today.

Comparing the Sphere 1 to Modern All-in-Ones

Just for fun, let‘s compare the Sphere 1‘s specs to a typical modern all-in-one PC like the 2020 Apple iMac 27":

Spec Sphere 1 (1975) iMac 27" (2020)
CPU Motorola 6800 @ 1MHz Intel Core i7 @ 3.8GHz
RAM 4KB (base), 64KB max 8GB (base), 128GB max
Storage Optional dual 8" floppies, 20MB HDD 512GB SSD + 1TB HDD
Display 12" monochrome CRT, 24×80 chars 27" 5K Retina LCD
I/O Ports Parallel, serial, analog, etc. Thunderbolt 3, USB-C, Wi-Fi, etc.
OS Built-in ROM monitor, optional disk OS macOS
Price (2021 dollars) ~$4,200 base $1,799 base

As you can see, the Sphere 1 was incredibly primitive by modern standards. Its CPU was 3,800 times slower than the iMac‘s and it had around 1/2,000,000th the RAM and 1/25,000th the storage. Yet in its design approach of packing a complete computer into one compact, integrated package, the Sphere 1 clearly anticipated the modern all-in-one PC.


The Sphere 1 may be largely forgotten today, but its place in PC history deserves to be celebrated. Its innovative all-in-one design, powerful hardware, and flexible expandability were years ahead of its time.

While it never achieved the mass-market success of later PCs like the Apple II, the Sphere 1 helped pave the way for the personal computer revolution. Its pioneering case design in particular was a major milestone in making computers more accessible, user-friendly, and "personal".

So the next time you‘re using a sleek modern all-in-one PC, take a moment to remember the little Sphere 1 and the visionary engineers who packed so much innovation into an 18-inch metal box back in 1975. While primitive by today‘s standards, the Sphere 1 was a vital evolutionary step between the hobby computers of the early 1970s and the true appliance-like PCs we enjoy today.


  1. Young, J. (2019). Sphere 1: The 1975 all-in-one computer that time forgot. Vintage Computer Festival Pacific Northwest. Retrieved from
  2. Wikipedia. (2021). Altair 8800. Retrieved from
  3. Trent, J. (2015). Early microcomputers: The Altair 8800 and other 1975 machines. Retrieved from
  4. Veit, S. (1993). Stan Veit‘s History of the Personal Computer. WorldComm.