On Mon, Jun 18, 2018 at 1:56 PM, Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:

> Just like I retold the Amdahl/Brooks story of the 8-bit byte and Amdahl
> thinking Brooks was nuts

Don't think I've heard that one?

Apologies for the repeat, if I have set this to TUHS before (I know I have mentioned it in other places). Somebody else on this list mentioned David Brailsford YouTube Video. Which has more details, biut he had some of not quite right. I had watched it an we were communicating. The actual story behind the byte is a bit deeper than he describes in the lecture, which he thanked me - as I have since introduced him to my old friend & colleague Russ Robelen who was was the chief designer of the Model 50 and later lead the ASC system with John Coche working for him. Brailsford is right about results of byte addressing and I did think his lecture is excellent and you can learn a great deal. That said, Russ tells the details of story like this:

Gene Amdahl wanted the byte to be 6 bits and felt that 8 bits was 'wasteful' of his hardware. Amdahl also did not see why more than 24 bits for a word was really needed and most computations used words of course. 4, 6-bit bytes in a word seemed satisfactory to Gene. Fred Brooks kept kicking Amdahl out of his office and told him flatly - that until he came back with things that were power's of 2, don't bother - we couldn't program it. The 32-bit word was a compromise, but note the original address was only 24-bits (3, 8-bit bytes), although Brooks made sure all address functions stored all 32-bits - which as Gordon Bell pointed out later was the #1 thing that saved System 360 and made it last.

BTW:

Russ and

Ed Sussenguth invented speculative execution for the ACS system

a couple of years later

. I was

harassing him

last January,

because for 40 years we have been using his cool idea and it

came back to bite us at Intel. Here is the message cut/pasted from his

email for context:

"I see you are still leading a team at Intel

developing super computers and associated technologies. It certainly

is exciting times in high speed computing.

It brings back memories of my last work at IBM 50 years ago on the ACS

project. You know you are old when you publish in the IEEE Annals of

the History of Computing. One of the co-authors, Ed Sussenguth, passed

away before our paper was published

in

2016.

https://www.computer.og/csdl/mags/an/2016/01/man2016010060.html

Some

of the work we did way back then has made the news in an unusual way
with the recent revelations on Spectre and Meltdown. I read the

‘Spectre Attacks: Exploiting Speculative Execution’ paper yesterday

trying to understand how speculative execution was being exploited.

At

ACS we were the first group at IBM to come up with the notion of the

Branch Table and other techniques for speeding up execution.

I wish you were closer. I’d do love to hear your views on the state of

computing today. I have a framed micrograph of the IBM Power 8 chip on
the wall in my office. In many ways the Power Series is an outgrowth

of ACS.

I still try to keep up with what is happening in my old field. The

recent advances by Google in Deep Learning are breathtaking to me.

Advances like AlphaGo Zero I never expected to see in my lifetime.
"

But you can lose with that strategy too.

Multics had a lot of sub-systems re-written from the ground up over time, and
the new ones were always better (faster, more efficient) - a common even when
you have the experience/knowledge of the first pass.

Unfortunately, by that time it had the reputation as 'horribly slow and
inefficient', and in a lot of ways, never kicked that:

http://www.multicians.org/myths.html

Sigh, sometimes you can't win!

Yep - although I think that may have been a case of economics. Multics for all its great ideas, was just a huge system, when Moores law started to make smaller systems possible. So I think your comment about thinking about what you need now and what you will need in the future was part of the issue.

I look at Multics vs Unix the same way I look at TNC vs Beowulf clusters. At the time, we did TNC, we worked really hard to nail the transparency thing and we did. It was (is) awesome. But it cost. Tru64 (VMS and other SSI) style clusters are not around today. The hack that is Beowulf is what lived on. The key is that it was good enough and for most people, that extra work we did to get rid of those seams just was not worth it. And in the because Beowulf was economically successful, things were implemented for it, that were never even considered for Tru64 and the SSI style systems. To me, Multics and Unix have the same history.

Multics was (is) cool; but Unix is similar; but different and too the lead. The key is that it was not a straight path. Once Unix took over, history went in a different direction.

Clem