A Memo on the Secret Features of the Hitachi 6309 processor (1992)

Re:A Memo on the Secret Features of the Hitachi 6309 process... by twic on Sunday November 10, 2019 @09:37AM (#21498076)

In this case, my guess would be that the 6309 was marketed as a drop-in compatible replacement for the Motorola 6809. In that case, there is no point advertising other features, because code written for the 6809 won't use them anyway. Rather, you market it on the fact that it's cheaper, uses less power, can be clocked higher, etc. Disclosing all sorts of ISA changes might even scare people off, thinking that the compatibility might be compromised.

So why did they put all those extra features in at all? My guess would be that they had a big buyer, who was in a position to write their own software to make use of those features. This is why you end up with undocumented features in Intel chips today, and the buyers are either big datacentre operators, like Google or Facebook, or government organisations, like the DoD or NSA.

I don't know who such a buyer would be for the 6309, though. It came out in 1982, the same year that Intel released the 286, and Motorola released the 68010 (and National Semiconductor released the NS32016). Also in 1982, Osaka University built what was then the world's fastest supercomputer using Z8001 microprocessors (check out the cooling system in the photo!):

http://museum.ipsj.or.jp/en/computer/other/0013.html

If you were a government agency, wouldn't you rather have a 16 MHz 32-bit 68k than a 5 MHz 8-bit 6309? Or even the 4-10 MHz 16-bit Z8001 that Osaka had used? Of course, if you were a Japanese government agency, you would have to import the 68k or Z-8001 from the USA, whereas the 6309 was made in Japan.

On the other hand, the Motorola 6809 was used for some arcade games, including Defender and Robotron. Maybe Hitachi planned to sell the 6309 to games companies? I assume that games companies controlled their entire software stack, and games always need more performance at an affordable price, so the 6309, as a 6809 but with opportunities to go faster, would have been pretty appealing. The arcade version of Double Dragon used the 6309, although five years after it came out:

https://en.wikipedia.org/wiki/Double_Dragon_(video_game)

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Re:A Memo on the Secret Features of the Hitachi 6309 process... by VLM on Sunday November 10, 2019 @10:55AM (#21498445)

I know for a fact that 90s era Liebert brand data center coolers used a 6809 based SCADA board. Presumably running microware OS-9. The business confusion at Hitachi was does management want us to innovate a hardware drop in replacement 2.0 for Liebert's coolers, or do they want us to just ship a second source for replacement parts for Liebert? Using Liebert solely as an example I'm aware of for actual customers.

Speed doesn't really matter to Liebert as its not like data center cooler thermostats are going to be typed on 10x faster by caffeinated humans or fans will spin 10x faster. Although denser code DOES mean more marketable features could be added to the firmware. Of course if you compile for the more advanced 6309 then you no longer have a second source for hardware and theoretically Hitachi could screw you over by charging a lot more than motorola charges for 6809 processors once you're dev team is stuck on the 6309. All I can say for certain is in the end, if you open a 90s era Liebert you'll see a thermostat / early-SCADA PCB with a genuine motorola 6809 on it, so that was THEIR final decision.

90s era Saturn automatic transmissions had a similar issue and they shipped with genuine motorola 68hc11 chips. Again, its not like a 10x faster processor will decrease 0-60 times by ten times, so ...

Generally Hitachi's business strategy WRT CPU licensing seems not to have worked?

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