Welcome to LinuxCNC.org

I run 32 bits because i see no advantage to 64 bit for me. All it does is break some things I like to use. So I could turn it around and ask the same question of you. Why 64 bits?

pfred1 wrote:
1) For amd64 arch the register sets are doubled, plus they are twice as wide, plus there are some auxilliary registers not seen on i586. And the cache lines are twice as wide, so more fits in the on processor instruction/data caches, 'cause the instructions aren't wider.

2) I like to keep my whole tool-chain 64-bits. Its just much faster.

3) 32-bits user space runs on 64-bit machines.

4)Whats apps are holding you back?

5) linuxcnc grip: there's no _amd64 repo so I can't apt-get source, and apt-get build-dep depends on a cooked kernel. Why?

Cheers
_jC
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_jC wrote:
My dual core i3 is a virtual 4 core in 32 bit Linux. I ran 64 bit on another machine (a core 2) but when I installed the 32 bit compat libs that system bombed, and I had to completely erase it and reload it. Fair to say 32 bit user space did not work well on it, or even work at all. Some mysterious process called sd(EXEC) just drove the system to its knees. It would have been a tough fix with a system load average of 23 and rising. Holding me back? Back from what? I'm pretty sure your subjectively faster tool chain is all in your head. If you've some verifiable proof I'd love to see it. Then again what you describe could be unique to AMD. I haven't run AMD since my old X2. The way you make it sound I guess I should be happy.

For historical reasons 'amd64' is the name given to x86 64-bit linux.

32-bit userspace is not required whatsoever, my system is 64 top-to-bottom.

But I do run 'draftsight', that pulls in the 32-bit compatibility stuff.

Sadly a 64-bit linuxCNC compliation is non-trivial, you pretty much have to build your own kernel and compile linuxCNC by hand.

My system is running on last May's Debian sid. The uptime was 6 weeks, and the max jitter of the base thread w/isocpu has been < 4500.

I am well satisfied that this is a robust system.

This past week I have taken the system down for integration, but I suppose I could post the kernel's .config if there is interest.

I am also well satisfied that 64 bits is just better, but I made that switch _years_ ago.

_jC
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_jC wrote:
I hate to be the one to burst your bubble but your general level of satisfaction today is not coming from you using 64 bit as opposed to 32. You've been a victim of a vicious set of circumstances that has falsely lead you to believe that, but it isn't so. Consider for a moment the time when you switched. Back then you were increasing your computing skills enough to take the plunge so to speak. I will also go out on a limb and say that over time you've improved your hardware situation somewhat as well. Those other factors are far more likely to have positively impacted you than what switching to 64 bits has done.

But your mind in order to come up with an explanation dredges up a definite moment, the switch to 64 bits, then attributes everything to it. What you've done is you've fallen into a common logic trap called drawing parallels where none exist. All religion, and much myth and legend was similarly born. So take heart, as what you've done is a pretty common thing for folks to do.

pfred1 wrote:
Thinking back I'm suprised that it is over 10 years ago now that I was lead test engineer on a rather large and thruput critical online transaction processing system. In this capacity I ran regressions of 64bit vs 32bit systems. I can say without hesitation that if a platform supports a mature 64bit implementation it will outpreform and outscale that same platform's 32bit implementation for all testcases except for spinlock().

But I do also undertand linuxCNC's desire to support the minimum covering subset of architectures.

Cheers
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