Linked by Thom Holwerda on Tue 29th Jan 2013 02:17 UTC
Hardware, Embedded Systems "The arithmetic-logic unit is a fundamental part of any computer, performing addition, subtraction, and logic operations, but how it works is a mystery to many people. I've reverse-engineered the ALU circuit from the 8085 microprocessor and explain how it works. The 8085's ALU is a surprisingly complex circuit that at first looks like a mysterious jumble of gates, but it can be understood if you don't mind diving into some Boolean logic."
Thread beginning with comment 550921
To view parent comment, click here.
To read all comments associated with this story, please click here.
RE[2]: Ok
by bassbeast on Wed 30th Jan 2013 17:38 UTC in reply to "RE: Ok"
bassbeast
Member since:
2007-11-11

Am I the only one that misses the old days when we had so many choices in both CPUs and even in X86? We had so many choices, Motorola and PPC and Intel, AMD, WinChip, Cyrix, so many choices! Remember what it was like when you could actually put a different CPU from a completely different company into a socket?

Now we only have 2 companies in X86 (three if you count Via but its nearly impossible to find) and while there are plenty of companies making ARM there just isn't the variation like we had.

Reply Parent Score: 2

RE[3]: Ok
by ameasures on Wed 30th Jan 2013 18:49 in reply to "RE[2]: Ok"
ameasures Member since:
2006-01-09

Am I the only one that misses the old days when we had so many choices in both CPUs and even in X86? ...


Yep I miss'em too. Not enough to want to go back there though. I remember tiptoeing around flaws in specific chips with particular operating systems.

Heck - even 287 chips that would throw a wobbly given a very specific combination of valid (FP) arithmetic inputs. It was reproduceable very consistently. Took a few engineers a while to spot that it was the chip, not the high level code and not the compiler!

Reply Parent Score: 2

RE[3]: Ok
by zima on Wed 30th Jan 2013 20:25 in reply to "RE[2]: Ok"
zima Member since:
2005-07-06

Am I the only one that misses the old days when we had so many choices in both CPUs and even in X86? We had so many choices, Motorola and PPC and Intel, AMD, WinChip, Cyrix, so many choices!

Yeah there were choices, but most (all?) of them much worse than today in performance per price...

And it seems you don't miss the old times that much yourself - you often write about the goodness that modern multicore x86 chips are.

Reply Parent Score: 2

RE[3]: Ok
by kwan_e on Wed 30th Jan 2013 22:55 in reply to "RE[2]: Ok"
kwan_e Member since:
2007-02-18

Now we only have 2 companies in X86 (three if you count Via but its nearly impossible to find) and while there are plenty of companies making ARM there just isn't the variation like we had.


There's MIPS. There's nVidia GPUs that doubles as super computers. There's Power/Cell. There's SPARC.

Reply Parent Score: 2