Aaaahhhh the sideburns Isaac, and that tie...
Byte January 1983 Back Cover
Asimov actually used the TRS-80, and the copy you can't read here extols the virtues of it and of SuperScripsit, his word processor of choice ("it has true proportional spacing for right and left margins and automatic pagination"). In a companion ad in Popular Computing, he's quoted, "During the day I might write about starships. At night I blast 'em on my TRS-80 Color Computer"

There's a later Tandy ad (Dec. 1984) with Bill Gates as the presenter. It's here as a larger image so you can read the copy. Wow, MS-Windows in colour!)

(The Model III was my first computer, CPM, 32k but I had only two dummy plastic covers where I'm sure Isaac had his 5 1/4" disk drives. With no floppy or hard drive, saving to a cassette recorder at 3am and getting a "Bad Save" error was hell.)