Linux cacheable memory usage vs Windows

Asustek computer inc. / K8n-e
December 24, 2009 at 21:35:43
Specs: Microsoft Windows XP Professional, 2.499 GHz / 2047 MB
I have a couple of old socket 7 systems that I was considering trying Linux on. Although these systems support up to 256MB (or more) RAM, only 64MB of that 256MB is cacheable.

As I recall, the problem with the way Windows reads RAM is that it reads from the top-down. In other words, if 256MB is installed, Windows would start with MB #256 & read downward toward MB #1, but the cacheable area would be from MB #1 thru MB #64. That means that 192MB would have to be used before the cacheable area is reached.

So, does anyone know in which direction Linux reads the RAM? Is it from the top-down like Windows (from 256MB to 1MB) or from the bottom-up (1MB to 256MB)?

Thanks & have a merry Christmas!


See More: Linux cacheable memory usage vs Windows

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#1
December 26, 2009 at 08:12:30
I started to look this up just to be sure and decided it can't possibly matter and was a trick question designed to make me go mad.

I'll ask an after Merry Christmas question. What do you care if the bits are upside down or not?


:)

Playing to the angels
Les Paul (1915-2009)


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#2
December 26, 2009 at 09:44:11
No, it's not a trick question at all. If you're willing to take the time, this old article will help explain:

http://www.pcguide.com/ref/mbsys/ca...

Here's a clip from another article explaining the same issue:

"Another example illustrates this point: Suppose your system's main memory cacheable limit is 64MB again, but now your system has been loaded to 80MB of main memory (16MB above the cacheable limit) and you were to run that same application and operating system ran in the previous example (the one requiring 6MB of main memory). The load "from the top" process, would mean that main memory locations 80MB-75MB would be filled. Since these main memory "locations" are above the main memory cacheable limit, the information stored at these main memory locations are not cacheable, and cannot use the cache memory as a fast retrieval storage bin. In this example, you will likely see a drop in system performance by exceeding the cacheable main memory limits of the system"

http://www.oempcworld.com/support/M...

The chart at the bottom for the following page lists the memory cache limits of older chipsets. Most of the old socket 7 boards I have laying around only cache 64MB. I realize that Win95 will run just fine on these systems, but who wants Win95 anymore?

http://www.computermemoryupgrade.ne...

One of my new year's resolutions is to unload the ancient hardware I have stacked up in my basement. I'm just trying to get a jump start on it. I'd prefer not to trash this stuff...I want to put together several useable systems, then give them away. If worse comes to worse, I'll just go with Win95 & be done with it, but if I can get a Linux distro to run decently, that would be my preference. I suppose the easist thing to do would just be to install 64MB RAM & try Damn Small or an older version of Puppy.


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#3
December 28, 2009 at 09:36:53
As I gather, L2 is only memory pointers to actual ram and depending on processor it is built in or through chipset l2. The reason it is faster is the pointer can directly go to the ram address that holds the data L2 only has address pointers it is not really faster ram as such. It does speed up the system as it doesn't have scroll to the ram address.

For each board and processor you'd have to decide the L2 config to decide how much tag-ram you have and how it works.

It is OS independent for the most part..

You could write your own kernel and compile each program exactly based on that information. Since you are selecting a generic kernel it will be based on a very large model base that will work for a range of processors and boards.

So it boils down to this. Do you want to optimize your OS for the exact board or do you wan to use a generic kernel and apps? I suspect the latter.

Boot to a floppy or cd and use dmsg | grep cache I think for info.


DSL seems to be the best choice from what I've used. There could be a case for xpud if all you want is a web access.

What do you want to do with the systems?

Playing to the angels
Les Paul (1915-2009)


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#4
December 29, 2009 at 21:12:33
"It does speed up the system as it doesn't have scroll to the ram address"

OK, I understand that & I want the system to be able to use the L2 "pointers" as much as possible rather than having to access the RAM directly. All these motherboards have the L2 onboard & can only cache up to 64MB. I realize that if I stick to just 64MB RAM, the L2 will be used as much as possible. But my question is, if I was to install 128MB, would Linux bypass the L2 pointers & go to the 64MB of uncached RAM 1st, just as Windows does? If so, I may as well stick to the 64MB limit but I suppose I can try both ways & see if there's a noticeable difference.

"What do you want to do with the systems?"

Like I said, I just want to get rid of some old hardware. I plan on assembling maybe 4-5 socket 7 systems & give them away, either to friends or I'll offer them up on freecycle. The configs will be something like this:

- Pentium 166MMX, 200MMX or 233MMX
- Intel 430FX or 430TX based socket 7 motherboard
- 64MB EDO SIMMs, possibly EDO DIMMs depending on the board
- 2-4MB PCI video
- network card, ISA or PCI
- sound card, ISA or PCI
- 4-6GB HDD
- basic CD-ROM drive
- AT case w/AT power supply, 200-250W

Do you think Puppy would run OK or should I stick with DSL? I also like Vector but I think that might be a little too much. I assume the people who will be getting these will be Linux newbs. I know you're much more learned in Linux than me so any advice you can give would be greatly appreciated. Thanks.


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#5
December 30, 2009 at 12:12:38
If you want the fastest linux you have to build it yourself. That would mean maybe a week or so on an old system to build a single purpose kernel and supported OS. This is by far the best solution to speed. One of the links talked about kernel issues with how to build for L2. See the LTSP and Linux from scratch documentation or just build a Gentoo system. Gentoo streamlined it a lot.Gentoo also supports a package management system

There are a few real time kernels that are gpl I think but they don't tend to speed up the user experience as such only how many tasks it can seem to handle. (my opinion)

Puppy is not as low ram as it sounds or as touted as. I think DSL is the best for a general solution.

The main issue with a non technical user trying linux is how they understand the whole process. They are unlikely to re-compile a kernel to add on a usb device or such. This leaves out most true from scratch builds.

You might get xbuntu or other low ram distros to work. See also old BeOS or QNX 5 (I think it was 5.2), BSD's and MenuetOS for one of the smallest OS's. Almost all of then would like more ram if possible, All need a swap file except Menuetos.


Try xpud on one of them too.


Playing to the angels
Les Paul (1915-2009)


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#6
December 30, 2009 at 21:39:24
I have a 200MMX system in the works and have also been wondering what to do with it instead of the multiboot 98SE/NT4.0/W2K thing I do with most of these old things.

I'm intrigued by the "If you want the fastest linux you have to build it yourself." thing; also the possibility of Gentoo.

But;

1....these things need to be pretty idiot proof when they go out the door

and

2...need to have a GUI that's easy to use.

I find it difficult to believe someone hasn't already done this and I (for one) haven't stumbled across it.

Skip


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#7
December 31, 2009 at 12:02:32
There is no idiot proof OS that I have seen.

A GUI should be idiot proof but it must be how people brains are hardwired. Some people I have tried to help can't use a GUI. I suspect the next step needs to be a talking computer and ask them what they want to do.

Playing to the angels
Les Paul (1915-2009)


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#8
December 31, 2009 at 22:38:08
I would be interested in how this would run, if you could install 128mb
http://forum.vectorlinux.com/index....

the problem with dsl, is they haven't released a new version in more than a 1.5 years.

larry


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#9
January 1, 2010 at 14:27:44
I was wondering about that too. It has been a long time for a new version but... If I wasn't so lazy I could roll my own version of dsl. Or pupppy or any for that matter.

Playing to the angels
Les Paul (1915-2009)


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#10
January 4, 2010 at 05:23:01
"the problem with dsl, is they haven't released a new version in more than a 1.5 years"

A 1.5 yr old version of DSL would be better than a 15 yr old version of Windows, I think?


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#11
January 4, 2010 at 13:28:48
Once installed you might be able to update some or most of DSL.

Seems John from DSL hasn't even logged into his forums since Feb 2009. Wonder if it is abandoned?

Playing to the angels
Les Paul (1915-2009)


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#12
January 5, 2010 at 13:50:43
jam makes a good point.

@jefro...the forum is still active but like you said, no sign of John.

Think I'll start with DSL and the best overclocking motherboard I have. Once that is sorted out, I'll probably change hdd's and give Puppy a shot; maybe Feather too.

I have plenty of PC66 memory to play with but I'm currently a little short of 32Mb sticks of 72pin stuff.

Skip


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#13
January 5, 2010 at 14:46:59
I have never known jam to make a bad point.

Playing to the angels
Les Paul (1915-2009)


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#14
January 6, 2010 at 15:04:47
Thanks for that jefro, but I think my wife would tell you differently ;-)

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#15
February 8, 2010 at 17:17:08
I cheated a little bit and put together a P200MMX clocked at 3.5x75 with 192Mb SDRAM. Motherboard is a PCChips M575 knockoff with an Ali Aladdin IV4+ chipset. Loaded W2K on a 3.5Gb partition with 2.5Gb reserved for a Linux distro.

Then the fun started...W2K is plenty snappy running Office 2000 Pro, IE6, FF, and old games like the original Age of Empires. DSL is also just as fast but; SLAX, Knoppix 3.7, Ubuntu 5.10 and a few other distros are real slugs or can't deal with the 1Mb video card I have installed. Puppy wasn't bad but wasn't good either.

I've pretty much eliminated hardware by running Prime95 overnight. Guess I'll download a few more flavors and keep at it but it's gettin' to be more trouble than it's worth.

Skip


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#16
February 10, 2010 at 02:53:38
And the winner is Puppy. It doesn't especially like ISA cards or really old video cards but it's the only relatively easy to install, configure, and use distro I tried with this old hardware.

Sure as hell it's head and shoulders above Win95 and NT4.

Skip


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#17
February 10, 2010 at 09:56:45
"on a 3.5Gb partition with 2.5Gb reserved for a Linux distro"
a small swap partition might help, even if its only 200mb.

larry


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#18
February 10, 2010 at 16:13:02
Tell ya the truth, I didn't even think of a swap partition. In other words, I didn't read the instructions for disk setup from puppy.org.

More pressing at the moment though is better video. This site is a PITA at 600x800 and nothing I've been able to do will set resolution at 1024x768. That resolution works fine on the W2K partition.

So; on to the next build with another 200MMX and a 3dfx Voodoo3 3000 AGP card.

If the video card fairy would just visit, I'm pretty sure most of my problems would go away. :)

Skip


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