Arch Linux

hex

Member

Registered: 2008-03-27

Posts: 6

The 4GB memory barrier

Hi

Since, as I understand it, 32-bit arch can't address more than 4GB of memory... that would include for instance 3GB + 2GB swap, correct? Im trying to recall the university course on operating systems I took a while back, but... my guess would be that you cannot access any memory space above 4GB in a 32bit environment, regardless of whether it happens to be actual ram or swap?

Which would mean that if I ever decided to go above the 2GB I currently have installed, it'd pretty much render a 32bit Arch useless. The problem I have with 64bit arch is simply that stuff just doesn't work. I spent 1.5 eternities trying to get flash running, and finally did it. Then, two days later, I suddenly have no sound in flash, with ndiswrapper giving me some random error. And I expect the same sort of fun will occur when I want to get some old windows games up and running through wine, and after that the list goes on I bet. So I'm thinking scrap Arch64, and install 32bit Arch instead. Less of a hassle. I'm sure everything will eventually work in 64bit arch as well, I just don't feel like dedicating 4 hours a day to solving problems that I could avoid by switching to 32bit. The only thing stopping me is the issue of memory above 4GB, and well.. in a year, will there even be computers with any less than 4GB ram?

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: The 4GB memory barrier

See thread and its reference to PAE.

Flash is garbage, regardless of the bits.

Sound issue might be an OSS vs ALSA (vs pulseaudio/dmix/esound/whatever) issue, if you have a non-hardware-mixing-soundcard. Software mixing in Linux is in a poor state.

Use kernel drivers in preference to ndiswrapper, if possible - the underlying Windows drivers could be buggy.

There are distros available which are easier to use

Dirhael

Member

From: /cold/north

Registered: 2008-03-12

Posts: 46

Re: The 4GB memory barrier

Swap doesn't count in the 4GB limit, but memory from things like your gfx/network/sound card does. Because of this, it's rarely that useful to have much over 3GB seeing as gfx cards these days often comes with +/-512MB alone.

zyghom

Member

From: Poland/currently Africa

Registered: 2006-05-11

Posts: 432

Website

Re: The 4GB memory barrier

I use 64GB in config and all is ok
or just 64bit distro - but lots of problems with soft then

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Zygfryd Homonto

hex

Member

Registered: 2008-03-27

Posts: 6

Re: The 4GB memory barrier

See thread and its reference to PAE.

Flash is garbage, regardless of the bits.

Sound issue might be an OSS vs ALSA (vs pulseaudio/dmix/esound/whatever) issue, if you have a non-hardware-mixing-soundcard. Software mixing in Linux is in a poor state.

Use kernel drivers in preference to ndiswrapper, if possible - the underlying Windows drivers could be buggy.

There are distros available which are easier to use

I sort of used the flash on arch64 guide, which includes using ndiswrapper. Are there any other solutions that actually work well?

And tbh, I've tried many distros over the year. Arch is by far the easiest to use. It's just that I don't feel like creating a ton of work when I don't have to. And the 32bit/4GB issue would be present on any operating system I would presume.

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: The 4GB memory barrier

You're confusing ndiswrapper (for wireless) with nspluginwrapper

gnash is an open-source alternative for flash, but is still in the early stages.

varl

Member

Registered: 2007-06-07

Posts: 51

Re: The 4GB memory barrier

If all you need is Youtube support, then swfdec and it's Mozilla-plugin is a easy, working possibility.

hex

Member

Registered: 2008-03-27

Posts: 6

Re: The 4GB memory barrier

Yes, of course, nspluginwrapper.

Well, according to http://ubuntuforums.org/showthread.php?t=643320 this might be a problem with the current version of mozilla... I seem to remember updating it not long ago, so that might've been what killed flash. Is there any clever way of reverting to an older version? Quite new to arch still, so it'll take me a while to get accustomed to the way things work.

Aaron

Member

From: PA, USA

Registered: 2007-12-19

Posts: 108

Website

Re: The 4GB memory barrier

Use a 32bit chroot, it should solve all your problems very simply.
http://wiki.archlinux.org/index.php/Arc … bit_system

And for your comment that stuff on "Arch64 just doesn't work."  I have to disagree whole-heartedly.
What exactly "Just doesn't work" besides flash?  That's a single thing, and I can assure  you it does work if you follow the wiki.

I only have 2gb of ram, and I still use Arch64.  It has a great 64bit community.

stylopath

Member

Registered: 2007-07-26

Posts: 112

Re: The 4GB memory barrier

flash works good with nspluginwrapper-ubuntu (from aur), if you only need youtube-support swfdec is the right choice.

wine on x64 works as well as on x86.

What else is a problem?

damjan

Member

Registered: 2006-05-30

Posts: 452

Re: The 4GB memory barrier

Since, as I understand it, 32-bit arch can't address more than 4GB of memory... that would include for instance 3GB + 2GB swap, correct? Im trying to recall the university course on operating systems I took a while back, but... my guess would be that you cannot access any memory space above 4GB in a 32bit environment, regardless of whether it happens to be actual ram or swap?

In 32-bit kernel and user-space, a *single* user-space process can't address more than 4GB (actually the limit is less, since there is the kernel-space/user-space split in the address-space). But you can still have as much swap as you want.

With a 32bit kernel, you can't have more that 4GB physical RAM, unless you use PAE which should enable up to 64GB(Ithink, 2^36) physical RAM.

Also you could use a 64-bit kernel with all the 32-bit userspace. This way, the kernel can handle up to 2^48 physical RAM, but it will also manage RAM much better from a 32-bit kernel even when you have 2GB+. Of-couse a single 32-bit process will not be able to allocate more than 4GB (but do you really have this kind of programs?).

For the 64-bit kernel/32-bit user-space rationalle you can also read Ted Tso's explanation:
http://mailman.linux-thinkpad.org/piper … 42289.html