[teddyh]

In early computing history, the unit of memory was not established yet, and different hardware architectures had different word sizes, not even necessarily evently divisible by 8. And the memory sizes of these machines used to be expressed using the naitive word size. Like “this machine has 8 kilowords of core”. Therefore, when I encounter an anachronistic memory size in old fiction, I just assume that I just don’t know the word size they are using.

[walrus01]

Gibson was also not a microcomputer enthusiast at the time he wrote the book, and didn't know much about the inner workings of PCs that ordinary people could afford with a regular amount of money in the late 70s/early 80s. As I recall he said he wrote the book on a typewriter. He's also on record as saying that the first half of the sequel in the series (Count Zero) was also written on a typewriter.

edit: But regarding your specific comment, it's true that memory size wasn't totally consistent in how it was described or marketed. But in terms of computers that you could purchase and fit in your house, if you look at things similar to Byte magazine from 1982, 1984 or whatever, it was pretty consistent that desktop microcomputers were specified in multiples of KB of RAM like a 64KB or 128KB commodore (or at the very low end 16KB or 32KB for something you would attach to your TV), or IBM PC/Clone that would ship with 512KB or 640KB or 1MB of RAM, and the more expensive ones having multiples of 1MB, 2MB, etc.

[teddyh]

The first home computers were all 8-bit machines, and memory sizes were therefore always specified in terms of 8-bit bytes. (This use then continued as the home computer market grew, and later completely dominated the field as mainframes declined.) But earlier, non-home, computers were as I described.

[marcosdumay]

The ALU of a computer with a megabit word must be a beast to awe upon!

[em3rgent0rdr]

Star Trek used the fictional "gigaquad" unit of computer data storage, and conveniently deliberately avoided defining how many bits the base unit of a "quad" is, so they never would get embarrassed if such an amount of storage became commonplace nowadays.