Don't let me derail the thread, though. 
Hahaha ... I
like tangents!
EDIT: Here's a Japanese article I just found that tells at least some of the story of how Sega chose the SH-2, from the perspective of a Hitachi engineer, published in an industry magazine in September 1997.
Thanks, that's very interesting.
Here's a Hitachi marketing-brief about the SH-2 from back around that time-period ...
http://www.hotchips.org/wp-content/uploads/hc_archives/hc06/2_Mon/HC6.S4/HC6.4.2.pdfWhen it comes to Sega, in addition to whatever poor choices the engineers were making, it seems to me that the executive side may have been steering them into bad ideas as well. Sega had a relationship with Hitachi - I think they were manufacturing the 68000s and other components in the Mega Drive, and there are even rumors that Hitachi execs and Sega execs were golfing buddies. Not to mention, I wouldn't be surprised if there was also a reluctance to use non-Japanese parts.
That sounds like your typical "business" scenario.
Hitachi's early CPU successes were in being a licensed second-source for American CPUs, and often improving them ... such as their HD64180 (improved Zilog Z80) and their HD6309 (improved Motorola 6809). Hitachi's relationship with Motorola gave them first the 6809, and then the 68000 (which they sold to Sega for the MegaDrive, and then also the Saturn).
AFAIK, the SuperH series (SH1, SH2, SH3) was one of their first home-grown designs ... and they made a bit of a mess of it.
It's still the only CPU that I know of that has 2 different instructions, with different names, and different binary codes, that do
exactly the same thing.
It also misses out a bunch of useful things, which means that you end up needing to use multiple instructions to accomplish what other RISC architectures can do with a single instruction.
Their "secret strategy" of throwing 2 SH-2 CPUs together in the Saturn and the 32X was an absolute joke, and just a marketing gimmick to claim double the processing power. In reality, the each CPU could pretty-much completely use the entire memory bandwidth by itself, and so pairing the 2 of them on a single bus just lead to massive bus-contention and starvation for each processor.
They tried to mitigate this by re-purposing the 4KB of write-through-cache into internal memory in order to reduce the bus-contention, but that was a joke because the 5th-generation machines were all supposed to be programmed in "C", and neither the language, nor any of Sega's libraries could actually take advantage of that little 4KB of uncontested memory.
Which is why nearly-all early Saturn games just disabled the 2nd CPU and ran entirely on the 1st CPU ... throwing away 50% of Sega's marketing-hype performance.
The PC-FX's V810 (and the PlayStation's MIPS R3000) don't have the raw fake-benchmark performance numbers of the SH-2, but they easily make up for it in practice by providing "usable" performance.
IMHO, the PlayStation is the 5th-generation equivalent of the PC Engine. It's an elegantly-designed machine that does exactly what it's designed to do, and does it very, very well. But since it's basically a super-Amiga, with a fast blitter for 2D games, and good-for-its-time-but-poor-in-hindsight 3D performance, it's just a little bit "boring" to program.
The PC-FX is like a C-programmable SuperGrafx, with some extra SNES-like background layers and video too. It's just a more-interesting 2D machine,
especially if you contemplate using the HuC6273 chip that's on the PC-FXGA to give you Saturn-like 3D capabilities (or just
lots of sprites).
