Is it ok to talk about "personal PCs", in the sense of distinguishing it from a work PC? Or would it be regarded as a case of RAS Syndrome?
Though the word personal is repeated in the expansion "personal personal computer", the two repetitions use different meanings of the same word. The first personal means "owned or used by a specific single person" (definition 1 here), while the second indicates "designed to be used by a single person" (definition 2 here, again). Both instances are required to convey the full idea and thus are not redundant. Consider the following examples spelled out in full:
- Personal PC: personal personal computer, (the usual case of a personal computer owned by a person)
- personal mainframe computer (I have a Cray in my bedroom),
- Public PC: public personal computer (a PC that is installed in a kiosk usable by anybody)
Like the other answer, I say that personal PC isn't redundant, but for different reasons. While PC does literally stand for personal computer, as opposed to a mainframe computer, the term picked up a lot of additional meaning over the last 40 years.
IBM's most successful personal computer line in the 1980s was called the IBM PC, and its popularity led to other manufacturers producing machines that had similar hardware configurations and were compatible with software written for the IBM PC, and thus became known as PC-compatible, so PC in general parlance came to refer to a specific type of personal computer, rather than all personal computers.
Later on (I believe late 80s/early 90s) Microsoft Windows came to be the dominant operating system for PC-compatible systems, and PC came to mean a personal computer that is running Windows. This is in part because the Intel x86 architecture that the IBM PC used more or less dominated the processor market at the time; the only significant competition was from computers made by Apple or licensed Macintosh clones, which used the unrelated PowerPC architecture.
PC still means Windows to this day, even though Apple switched to x86 about a decade ago and there are now versions of Windows that run on other architectures, like ARM. So personal PC is a perfectly reasonable construction, especially if you're referring to a Windows computer that's owned for personal use.