
A Memo on the Secret Features of the Hitachi 6309 processor (1992) - mmoez
https://en.wikichip.org/wiki/hitachi/6309/a_memo_on_the_secret_features_of_6309
======
PaulHoule
I had TRS-80 color computers throughout the 1980s before I did a data
processing job for my Uncle and used the money to get a 286 PC.

The CoCo3 had a memory management unit similar to the PDP-11 minicomputers
which could do very coarse paging. I ran an operating system called OS/9 which
was a minaturized Unix, I had a few UARTS and two terminals plugged in: a
TRS-80 Model 100 and an old Dec Correspondent printing terminal.

There are many "paths not taken" in the computer industry, but surely Radio
Shack thought about a Coco 4 which could go up against the Amiga -- the 68k
had the dirty secret that it didn't perform better than upgraded versions of
the 6502, 6809, Z80, etc.

The Apple ][gs was a similar dead-end. Steve Jobs underestimated the lifespan
of the Apple ][, so he rushed to make the non-compatible Apple ///, the
expensive Lisa, the underpowered first Macintosh.

In the meantime Apple ][ had a durable lead and Apple kept upgrading it in
little ways.

[https://en.wikipedia.org/wiki/Apple_IIGS](https://en.wikipedia.org/wiki/Apple_IIGS)

It had an underclocked

[https://en.wikipedia.org/wiki/WDC_65C816](https://en.wikipedia.org/wiki/WDC_65C816)

which could address 24-bit extended memory, just like a System/360 of old (way
bigger than the PDP-11.)

It was underclocked because an unhobbled Applie ][gs would outperform a much
more expensive Mac 2.

Apple stagged through multiple near-death experiences with the Mac. What if
Apple had kept the ][ line going and built on the momentum that the ][ had?
Today we might be running a 64-bit derivative of the 6502!

~~~
acqq
> Today we might be running a 64-bit derivative of the 6502!

The designers of ARM used 6502 before and one of designers admits there was
some inspiration from that:

[https://people.cs.clemson.edu/~mark/admired_designs.html#wil...](https://people.cs.clemson.edu/~mark/admired_designs.html#wilson)

"I learned about pipelines from it (by comparison with the 6800) and its
designers were clear believers in the KISS principle. Plus the syntax of its
assembler and general accessibility of it from the machine code perspective. I
can still write in hex for it - things like A9 (LDA #) are tattoed on the
inside of my skull. The assembly language syntax (but obviously not the
mnemonics or the way you write code) and general feel of things are
inspirations for ARM's assembly language and also for FirePath's. I'd hesitate
to say that the actual design of the 6502 inspired anything in particular -
both ARM and FirePath come from that mysterious ideas pool which we can't
really define (its hard to believe that ARM was designed just from using the
6502, 16032 and reading the original Berkeley RISC I paper - ARM seems to have
not much in common with any of them!)."

------
twic
> The features was originally reported in a magazine, Oh!FM (1988 Apr.), which
> was written in Japanese.

Fun fact [0]: Oh!FM was published by SoftBank [1]. It, and a bunch of other
magazines called Oh!${arch}, were Masayoshi Son's second line of business,
after the computer parts store which started it all.

[0] for small values of fun

[1]
[https://www.msx.org/wiki/Oh!_Hit_Bit](https://www.msx.org/wiki/Oh!_Hit_Bit)

------
ahmedfromtunis
Any idea on why would a company keep some features as a secret and not use
them as a competitive advantage against competitors? Was this to protect
another (costlier) line of products?

~~~
twic
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](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)](https://en.wikipedia.org/wiki/Double_Dragon_\(video_game\))

~~~
VLM
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?

