AMD's Athlon 64 X2 3800+ processor

AMD's Athlon 64 X2 3800+ processor
Let the upgrades begin
by Scott Wasson — 2:26 AM on August 1, 2005 for THE TECH REPORT

WHEN WE FIRST reviewed the Athlon 64 X2 processor a few months back, we said that it was an outstanding CPU, but we wished out loud for AMD to start selling a 2GHz version of the X2 at a lower price. After all, we argued, Intel's Pentium D 820 is a killer deal at just under $250, while the least expensive Athlon 64 X2 costs over twice that. Sure, the X2's performance might well justify the price premium, but we'll take more for our money when we can get it.

Today, our wish is fulfilled in the form of the Athlon 64 X2 3800+, a dual-core processor running at 2GHz with 512K of L2 cache per core. AMD has priced this baby at $354—significantly less than any of its other dual-core products. It doesn't take a Ph.D. in computer engineering to figure out that the X2 3800+ ought to offer a very potent combo of price and performance.

As is our custom, we compared the X2 3800+ against over a dozen single- and dual-core competitors to see just how it fits into the big picture. Then we overclocked the living daylights out of the thing, and everything went soft and fuzzy. Our heads are still spinning. Keep reading to see why.

Code name: Manchester
Our first exposure to the Athlon 64 X2 came in the form of the 4800+ model. That chip is code-named "Toledo," and it packs 1MB of L2 cache per processor core, as do the dual-core Opterons. Toledo-core chips sport a transistor count of about 230 million, all crammed into a die size of 199 mm².

AMD also makes several models of Athlon 64 X2 that have only 512K of L2 cache. In the past, CPUs with smaller caches have sometimes been based on the exact same chip as the ones with more cache, but they'd have half of the L2 cache disabled for one reason or another. That's not the case with the X2 3800+. AMD says this "Manchester"-core part has about 154 million transistors and a die size of 147 mm², so it's clearly a different chip. AMD rates the max thermal power needed to cool the X2 3800+ at 89W—well below the 110W rating of the 4800+—and they've revised down the max thermal power of the X2 4200+ to 89W, as well. The Manchester core is obviously a smaller, cooler, and cheaper-to-manufacture chip than Toledo.

The Athlon 64 X2 3800+ Cosmetically, though, you'd never know it, because the X2 3800+ looks like pretty much any other Socket 939 processor. The X2 3800+ is intended to work with AMD's existing Socket 939 infrastructure, and it may well be an upgrade option for current owners of Athlon 64 systems. You'll want to check with your motherboard maker to see whether or not your board will support an X2 before making the leap, though. Some boards need only a BIOS update, but we're finding out that some others just can't handle X2 processors. Most newer motherboards should be fine.

Before we dive into the benchmark numbers, let's have a quick look at where the X2 3800+ fits into the bigger picture. With its introduction, the Athlon 64 X2 family now looks like so:

CPU	Clock speed	L2 cache size	Price
Athlon 64 X2 3800+	2.0GHz	512KB	$354
Athlon 64 X2 4200+	2.2GHz	512KB	$482
Athlon 64 X2 4400+	2.2GHz	1024KB	$537
Athlon 64 X2 4600+	2.4GHz	512KB	$704
Athlon 64 X2 4800+	2.4GHz	1024KB	$902

At $354, the X2 3800+ isn't exactly cheap, but it does extend the X2 line into more affordable territory. You've probably noticed the apparent hole in the X2 models at 4000+. Logic would dictate that the X2 4000+ would run at 2GHz and have 1MB of L2 cache. So where is it? I asked AMD this very question, and they told me that they won't comment on unannounced products—and besides there aren't any plans for an X2 4000+ right now.

I'm not too broken up about that, because I'm not convinced the additional L2 cache is worth paying more money to get. We'll address that issue in more detail when we look at the benchmark results.

Now for something really confusing. How does the Athlon 64 X2 3800+ stack up against the competition? Figuring out such things has become horribly puzzling as Model Number Mania has taken hold of the CPU market. Here's my attempt at lining up the various AMD and Intel CPU models according to rough price parity:

CPU	Price	CPU	Price	CPU	Price	CPU	Price	CPU	Price
Pentium 4 541	$218	Pentium 4 630	$224			Athlon 64 3200+	$194
Pentium 4 551	$278	Pentium 4 640	$237	Pentium D 820	$241	Athlon 64 3500+	$223
				Pentium D 830	$316	Athlon 64 3800+	$329	Athlon 64 X2 3800+	$354
Pentium 4 561	$417	Pentium 4 650	$401			Athlon 64 4000+	$375
								Athlon 64 X2 4200+	$482
				Pentium D 840	$530			Athlon 64 X2 4400+	$537
Pentium 4 571	$637	Pentium 4 660	$605					Athlon 64 X2 4600+	$704
		Pentium 4 670	$851			Athlon 64 FX-55	$827
		Pentium 4 XE 3.73GHz	$999	Pentium XE 840	$999	Athlon 64 FX-57	$1031	Athlon 64 X2 4800+	$902

From this handy table, we learn that the X2 3800+'s dual-core competition from Intel is probably the Pentium D 830. You can have a single-core Pentium 4 551 for about 75 bucks less than the price of the X2 3800+, or you could pick up AMD's single-core Athlon 64 3800+ in the same basic price range as the "equivalent" X2. The Athlon 64 3800+ runs at 2.4GHz and has a 512K L2 cache, so you lose 400MHz and pick up a whole second CPU core by going for the X2 3800+ instead. I'd say that's an easy tradeoff to make, but the benchmark results will tell us more about the shape of that choice.

AMD's dual-core Opteron processors

AMD's dual-core Opteron processors
Because four is better than two
by Scott Wasson — 5:16 AM on April 21, 2005 for THE TECH REPORT

MICROPROCESSORS ARE GETTING too hot, requiring too much power, and not delivering enough additional performance for it. That's the basic problem. The engine that's driven the microcomputer's incredible rise in capability over the past 30 years, Moore's Law, isn't quite out of steam yet, but some of its offshoots are on the ropes. CPU designers have nearly exhausted their collective bag of tricks to get more performance out of additional transistors on a chip by increasing parallelism at the instruction level. Speculative execution and deep pipelining are by now very standard features, and CPU designs are getting increasingly complex and hard to manage. When Gordon Moore's goose lays a golden egg and the number of transistors possible on a chip doubles, as it is supposed to do every 18 months, taking advantage of the windfall has proven increasingly difficult.

Cranking up clock speeds hasn't helped much, either, because of transistor leakage problems. Chips are sucking up large amounts of power and expending much of it as heat, and the problem grows more acute as clock speeds ramp up. The most widely noted example of these problems, by far, has been at the company Moore co-founded. The power, heat, and speed problems of the "Prescott" core inside of recent Pentium 4 processors prompted Intel into an impressive and very public change of direction over the course of the past year. The company has sworn off the quest for 4GHz, shied away from clock speed as a measure of performance, and utterly rewritten its CPU roadmap.

AMD has not been entirely immune to these problems, but it has sidestepped their worst effects by keeping clock speeds down. The original Opteron processor debuted two years ago today at speeds up to 2GHz. Two years later, the same processors are available at 2.6GHz—only a 600MHz increase, not much in the grand scheme.

Fortunately, both AMD and Intel seem to have settled on an answer that should allow them to take advantage of ballooning transistor counts to gain additional performance: thread-level parallelism. By dialing back clock speeds and putting multiple CPU cores on a chip, the theory goes, processor performance can rise as transistor counts do. This sort of parallelism will, of course, be familiar to those who know a thing or two about Opteron processors, which have commonly been employed in pairs as part of server or workstation systems.

In fact, AMD says that the Opteron was designed from the outset with dual-core implementations in mind. The folks there are also quick to remind anyone who will listen that AMD was first to tape out an x86-compatible dual-core design and first to demonstrate such a beast in public. Today, they aim to be the first manufacturer to deliver dual-core x86 processors for workstations and servers, just days after Intel officially announced its first dual-core desktop processors.

We've had a pair of dual-core Opteron processors on the test bench for some time now, and we're pleased to report some rather impressive results. AMD's dual-core design is something more than just a pair of CPUs glued together on a single piece of silicon, and this design choice yields a performance dividend. Keep reading to see how the new Opteron 275 stacks up against its Opteron predecessors and against Intel's latest "Nocona" Xeons. We also have a head-to-head battle of single-socket, dual-core workstation processors: the Opteron 175 versus the Pentium Extreme Edition 840.

The processors
On looks alone, one would be hard pressed to tell the difference between dual-core Opterons and their single-core counterparts.

They're cosmetically identical, save for the slightly revamped model numbering scheme. The three-tiered processor series convention remains intact. 100 series processors are for single-socket systems, the 200 series for dual, and the 800 series is intended for 4-socket systems or better. However, instead of incrementing the tail end of the model number by two as clock speeds ramp up, as the Opterons 246, 248, and 250 did, the dual-core models will come in increments of five. The first dual-core Opterons will arrive at clock speeds of 1.8, 2.0, and 2.2GHz as models x65, x70, and x75, respectively.

Prices will vary according to whether the chips are part of the 100, 200, or 800 series and according to clock speeds, but the general plan for pricing is fairly straightforward: it's almost as if AMD were introducing three new top-end speed grades at once. However, there is some overlap. For instance, the Opteron 252 is priced at $851, and the Opteron 265 will be priced the same. Consumers can choose whether they wish to purchase a dual-core processor at 1.8GHz or a single core at 2.6GHz for the same amount. The higher models will carry a premium, but AMD plans to bring the prices of dual-core Opterons down over time into the territory of the current single-core models.

The even better news for current owners of Opteron systems is that the dual-core Opterons will be pin-compatible with existing Socket 940 systems, capable of acting as drop-in replacements for current single-core models. The only requirement is that the motherboard must be able to support newer 90nm chips like the Opteron 252. If the board can do that, it should be able to handle the dual-core chips after a BIOS update, AMD claims. (Check with your motherboard maker to be sure.)

In order to pull off this impressive feat of backward compatibility, AMD had to make its dual-core parts fit into the same basic power and heat envelopes as its single-core processors. To do so, the company tweaked its fabrication process, using lower-leakage transistors that switch somewhat slower but waste less power, among other things. As a result, the Opteron 275 tops out at 2.2GHz, but it consumes no more power than the Opteron 252 at 2.6GHz.

This is one of the minor miracles of choosing thread-level parallelism over higher clock speeds. When we asked AMD CTO Fred Weber about how they managed to keep power and heat so low, he was coy about which specific optimizations AMD employed, but he offered some examples. When you're not optimizing for the absolute best linear performance, he noted, many things are possible, including everything from changing the oxide thickness and transistor voltages to resizing buffers and more extensive clock gating.

To further manage heat and power, dual-core Opterons will support AMD's PowerNow feature (also known as Cool'n'Quiet in the desktop world) that scales clock speeds and CPU voltages down at times of low CPU loads. This feature will function on a whole-chip basis; the CPU cores will not scale their clock speeds up and down independently.

As for the chip itself, the dual-core Opteron will be manufactured on AMD's 90nm process with silicon-on-insulator (SOI) technology. The chips will include all of the latest enhancements AMD has made to the K8 core, including SSE3 support and an improved memory controller with broader compatibility, improved memory loading, and more efficient memory mapping.

A dual-core Opteron chip packs in about 233 million transistors, and its die size is a very healthy 199 mm². The Intel Prescott/Nocona on which the Xeon is based is 112 mm² with roughly 125 million transistors. (The newer version with 2MB of L2 cache has 133 million transistors.) So the dual-core Opteron is large, but it's also a very close match for Intel's "Smithfield" dual core, which weighs in at roughly 230 million transistors and 206 mm², although estimates and methods of counting transistors can vary.

RSS - Rich Site Summary

Or Really simple syndication. Whichever it is, the concept is really novel and useful for the average internet using public.But more than three-quarters of the experienced or amateur surfing population doesn't know WHAT it is and how useful this is.The ignorance levels are appalling that when we had decided on a mini project ,a simple "Desktop Feed Aggregator/Reader" many of them sat with a gaping mouth and bulging eyeballs.So what is this RSS ?and how is it useful ? Here I am going to touch upon RSS and how to go about making your own feeds.

WIKIPEDIA says RSS (formally "RDF Site Summary", known colloquially as "Really Simple Syndication") is a family of webfeeds formats used to publish frequently updated content such as blog entries, news headlines or podcasts. An RSS document, which is called a "feed", "web feed", or "channel", contains either a summary of content from an associated web site or the full text. RSS makes it possible for people to keep up with their favorite web sites in an automated manner that's easier than checking them manually.

Thats it! You can check for updates using a feed reader rather than going to a site.Imagine checking your college site for any updates,every hour. Subscribing to a feed is really simple if you are using FireFox.It has a simple enough RSS Reader thats inbuilt.Whenever you visit a site that's syndicated,a
bright orange tab can be seen at the right end of the address bar.Click on it, and choose your preferred reader.

Building personal RSS feed,
step by step

At start, this is just a simple text file, created with any text
editor. But an XML editor is more convenient. The name may be, for example: "feed.xml".
The overall structure is as that:

<?xml version="1.0" ?> <rss version="2.0"> <channel> </channel> </rss>

1) Define the source, by the channel tag

The channel will be the same for all your RSS feeds. These tags
are required:
- title: the title of your website, may be the one in the
title tag of the home page.
- link: the URL of your website: example: http://www.xul.fr
- description: description of your website, about 200 characters,
this may be the text assigned to the content attribute of the
description tag, in the head section of the home page.

<channel> <title>XUL and XML</title> <link>http://www.xul.fr/</link> <description>Xml graphical interface etc...</description> </channel>

2) Add an image

This is optional. Design a small image (88x31 for example) in a common format
(gif, jpg, png) and put in into the same directory that the RSS file.
The "image" tag is a sub-element of the channel tag
- url is the address of the image itself.
- link is the address of the page displayed when one clicks on the
image.

<channel> <title> </title> <link> </link> <image> <url>http://www.xul.fr/xul.gif</url> <link>http://www.xul.fr/index.html</link> </image> </channel>

3) Add a new item

Now, we will add a web page to display an information. This is
an "item" tag, a sub-element of channel, and this components
are required:
- title: the title of the article.
- link: the URL of the page.
- description: a summary of the article, about 200 characters.

<item> <title>News of today</title> <link>http://www.xul.fr/xml-rss.html</link> <description>All you need to know about RSS</description> </item>

4) Add more items

More items may be added to this channel.

5) Upload the file

Put the feed.xml file into your website, among other web pages.

6) Validate the file

You may use this online RSS
feed validator.

7) Make it available

This is accomplished by adding an RSS button on the home page. A click on

the button should display the XML file you have created.

<a href="http://www.xul.fr/feed.xml> <img src="rss.gif"> </a>

If the image is not displayed, use a complete URL, as http://www.xul.fr/rss.gif,
for example.

8) Updating the feed

To publish further articles, you have just to add items, and
remove older ones to keep the number of articles constant.

Passwords . A New Perspective

Text in itallics represent my views. The rest are quoted.

This article refers only to those Passwords that are used to login into online systems like email accounts, or services.Having been introduced to the backend and frontend of the virtual world simultaneously has helped me to gain that special insight into the working of the internet.Although i dont profess to be much of an expert to offer advice,i feel qualified enough to assess the present situation in these areas and write upon it.
A basic Login authentication system contains a database that keeps the information that users submit upon registration.i.e your passwords are indeed stored somewhere and can be seen by the system administrator.Most decent web service providers (eg: yahoo , gmail ... amazon...) do not store the passwords in plain text form rather they are encrypted.A simple one way encryption algorithm , that i have used is MD5.Its too big to write in one blog.Maybe I'll write upon MD5 and methods to decrypt in another post.maybe...
That they are encrypted , is the reason why you can never ask the providers to give you the password.One can only reset it.
So the point is , all information that is submitted is stored and is viewable by a human.
Whenever a user requests access to a login secured page, the password that is provided along with the username is checked with the ones in database and if it matches, the user is logged in.Basic hack attempt starts here.

Passwords Reveal Your Personality
A spontaneously-generated password may be more revealingthan you think.
The random catchphrase that accesses your e-mail account may unlock your psyche as well as your correspondence, say experts..
The study identified four password "genres." "Family-oriented" respondents numbered nearly half of those surveyed. These people select their own name or nickname, the name of a child, partner or pet, or a birth date. They tend to be occasional computer users and have strong family ties. "They choose passwords that symbolize people or events with emotional value," Indeed. One third of respondents were "fans," using the names of athletes, singers, movie stars, fictional characters or sports teams. Fans are young and want to ally themselves with the lifestyle represented by a celebrity. Two of the most popular names were Madonna and Homer Simpson. Eleven percent of responses were from "fantasists." Their interest in sex is evident in passwords such as "sexy," "stud" and "goddess." "Traditionally, these individuals are male, but 37 percent of fantasists identified themselves as female," . The final ten percent of participants are "cryptics," because they pick unintelligible passwords or a random string of letters, numerals and symbols, such as Jxa+157. Petrie says cryptics are the most security-conscious group. They tend to make the safest but least interesting choices.

Passwords are inadvertently revealing for two reasons. First, they are generated on the spot. "Since you're focused on getting into the system, you're likely to put down something that comes readily to mind," . "In this sense, passwords tap into things that are just below the surface of consciousness, much the way Rorschach and word-association tests do. Also, to remember your password you pick something that will stick in your mind. You may unconsciously choose something of particular emotional significance."

I personally vouch for all the four genres, i have seen people using all of the above mentioned four.
Additionally there's one more group of people who belongs to the category "stupid" for the zillions who use "Trustno1", "Swordfish", "Password","qwerty","123456","abc123"..... the only reason they're ever considered passwords are ,because they're 6 letters long.

Password psychology is a field of cryptography and psychology that studies how passwords are chosen and what determines users to choose a certain password. The discipline reveals several details about the way users remember and choose passwords, allowing system administrators to improve the safety of the passwords

Basic studies

It has been demonstrated that users usually remember passwords by associating them with something. This is done either mnemonically, where users associate letters and numbers with a certain meaning, or mechanically, learning the password by heart but associating it with a certain movement of their fingers on the keyboard. For example, a Pink Floyd fan may remember gbBs2u as "good bye Blue sky to you" (close to the lyrics of a Pink Floyd song). Other users may have no other alternative than learning the password by heart. However, it will be more difficult for them to remember it when using a different keyboard map, even when the keyboard map is only slightly different (for example, Eastern keyboard maps often interchange the location of the Y and Z keys on Western keyboard maps).

These studies were a stepping stone in discovering several yet unknown facts about password choices, allowing some cryptographic schemes to be developed separately, especially for people with disabilities, for example.

But the fact remains.The average internet users are dumb.And the remaining ones,well, they aren't

VI - Some useful commands

• a enter insert mode, the characters typed in will be inserted after the current cursor position.
• h move the cursor to the left one character position.
• i enter insert mode, the characters typed in will be inserted before the current cursor position.
• j move the cursor down one line.
• k move the cursor up one line.
• l move the cursor to the right one character position.
• r replace one character under the cursor. Specify count to replace a number of characters
• u undo the last change to the file. Typing u again will re-do the change.
• x delete character under the cursor.
• yy yank until , putting the result into a buffer. "yy" yanks the current line. a count yanks that many lines. The buffer can be specified with the " command. If no buffer is specified, then the general buffer is used.
• p paste
• o Enter insert mode in a new line below the current cursor position.
• % Move the cursor to the matching parenthesis or brace.
• / Search the file downwards for the string specified after the /
• ? Search the file upwards for the string specified after the ?.
• ~ Switch the case of the character under the cursor.
• R Replace characters on the screen with a set of characters entered, ending with the Escape key.
• S Change an entire line.

My browser crashed atleast three times while writing this blog! That's VI

All about Linux swap space

By Gary Sims on December 03, 2007 at Linux.com

When your computer needs to run programs that are bigger than your available physical memory, most modern operating systems use a technique called swapping, in which chunks of memory are temporarily stored on the hard disk while other data is moved into physical memory space. Here are some techniques that may help you better manage swapping on Linux systems and get the best performance from the Linux swapping subsystem.

Linux divides its physical RAM (random access memory) into chucks of memory called pages. Swapping is the process whereby a page of memory is copied to the preconfigured space on the hard disk, called swap space, to free up that page of memory. The combined sizes of the physical memory and the swap space is the amount of virtual memory available.

Swapping is necessary for two important reasons. First, when the system requires more memory than is physically available, the kernel swaps out less used pages and gives memory to the current application (process) that needs the memory immediately. Second, a significant number of the pages used by an application during its startup phase may only be used for initialization and then never used again. The system can swap out those pages and free the memory for other applications or even for the disk cache.

However, swapping does have a downside. Compared to memory, disks are very slow. Memory speeds can be measured in nanoseconds, while disks are measured in milliseconds, so accessing the disk can be tens of thousands times slower than accessing physical memory. The more swapping that occurs, the slower your system will be. Sometimes excessive swapping or thrashing occurs where a page is swapped out and then very soon swapped in and then swapped out again and so on. In such situations the system is struggling to find free memory and keep applications running at the same time. In this case only adding more RAM will help.

Linux has two forms of swap space: the swap partition and the swap file. The swap partition is an independent section of the hard disk used solely for swapping; no other files can reside there. The swap file is a special file in the filesystem that resides amongst your system and data files.

To see what swap space you have, use the command swapon -s. The output will look something like this:

Filename        Type            Size    Used    Priority
/dev/sda5       partition       859436  0       -1

Each line lists a separate swap space being used by the system. Here, the 'Type' field indicates that this swap space is a partition rather than a file, and from 'Filename' we see that it is on the disk sda5. The 'Size' is listed in kilobytes, and the 'Used' field tells us how many kilobytes of swap space has been used (in this case none). 'Priority' tells Linux which swap space to use first. One great thing about the Linux swapping subsystem is that if you mount two (or more) swap spaces (preferably on two different devices) with the same priority, Linux will interleave its swapping activity between them, which can greatly increase swapping performance.

To add an extra swap partition to your system, you first need to prepare it. Step one is to ensure that the partition is marked as a swap partition and step two is to make the swap filesystem. To check that the partition is marked for swap, run as root:

fdisk -l /dev/hdb

Replace /dev/hdb with the device of the hard disk on your system with the swap partition on it. You should see output that looks like this:

 Device Boot    Start   End     Blocks  Id      System
/dev/hdb1       2328    2434    859446  82      Linux swap / Solaris

If the partition isn't marked as swap you will need to alter it by running fdisk and using the 't' menu option. Be careful when working with partitions -- you don't want to delete important partitions by mistake or change the id of your system partition to swap by mistake. All data on a swap partition will be lost, so double-check every change you make. Also note that Solaris uses the same ID as Linux swap space for its partitions, so be careful not to kill your Solaris partitions by mistake.

Once a partition is marked as swap, you need to prepare it using the mkswap (make swap) command as root:

mkswap /dev/hdb1

If you see no errors, your swap space is ready to use. To activate it immediately, type:

swapon /dev/hdb1

You can verify that it is being used by running swapon -s. To mount the swap space automatically at boot time, you must add an entry to the /etc/fstab file, which contains a list of filesystems and swap spaces that need to be mounted at boot up. The format of each line is:

Since swap space is a special type of filesystem, many of these parameters aren't applicable. For swap space, add:

/dev/hdb1       none    swap    sw      0       0

where /dev/hdb1 is the swap partition. It doesn't have a specific mount point, hence none. It is of type swap with options of sw, and the last two parameters aren't used so they are entered as 0.

To check that your swap space is being automatically mounted without having to reboot, you can run the swapoff -a command (which turns off all swap spaces) and then swapon -a (which mounts all swap spaces listed in the /etc/fstab file) and then check it with swapon -s.

Swap file

As well as the swap partition, Linux also supports a swap file that you can create, prepare, and mount in a fashion similar to that of a swap partition. The advantage of swap files is that you don't need to find an empty partition or repartition a disk to add additional swap space.

To create a swap file, use the dd command to create an empty file. To create a 1GB file, type:

dd if=/dev/zero of=/swapfile bs=1024 count=1048576

/swapfile is the name of the swap file, and the count of 1048576 is the size in kilobytes (i.e. 1GB).

Prepare the swap file using mkswap just as you would a partition, but this time use the name of the swap file:

mkswap /swapfile

And similarly, mount it using the swapon command: swapon /swapfile.

The /etc/fstab entry for a swap file would look like this:

/swapfile       none    swap    sw      0       0

How big should my swap space be?

It is possible to run a Linux system without a swap space, and the system will run well if you have a large amount of memory -- but if you run out of physical memory then the system will crash, as it has nothing else it can do, so it is advisable to have a swap space, especially since disk space is relatively cheap.

The key question is how much? Older versions of Unix-type operating systems (such as Sun OS and Ultrix) demanded a swap space of two to three times that of physical memory. Modern implementations (such as Linux) don't require that much, but they can use it if you configure it. A rule of thumb is as follows: 1) for a desktop system, use a swap space of double system memory, as it will allow you to run a large number of applications (many of which may will be idle and easily swapped), making more RAM available for the active applications; 2) for a server, have a smaller amount of swap available (say half of physical memory) so that you have some flexibility for swapping when needed, but monitor the amount of swap space used and upgrade your RAM if necessary; 3) for older desktop machines (with say only 128MB), use as much swap space as you can spare, even up to 1GB.

The Linux 2.6 kernel added a new kernel parameter called swappiness to let administrators tweak the way Linux swaps. It is a number from 0 to 100. In essence, higher values lead to more pages being swapped, and lower values lead to more applications being kept in memory, even if they are idle. Kernel maintainer Andrew Morton has said that he runs his desktop machines with a swappiness of 100, stating that "My point is that decreasing the tendency of the kernel to swap stuff out is wrong. You really don't want hundreds of megabytes of BloatyApp's untouched memory floating about in the machine. Get it out on the disk, use the memory for something useful."

One downside to Morton's idea is that if memory is swapped out too quickly then application response time drops, because when the application's window is clicked the system has to swap the application back into memory, which will make it feel slow.

The default value for swappiness is 60. You can alter it temporarily (until you next reboot) by typing as root:

echo 50 > /proc/sys/vm/swappiness

If you want to alter it permanently then you need to change the vm.swappiness parameter in the /etc/sysctl.conf file

Conclusion

Managing swap space is an essential aspect of system administration. With good planning and proper use swapping can provide many benefits. Don't be afraid to experiment, and always monitor your system to ensure you are getting the results you need.

Classic Sherlock Holmes Quotes

• My name is Sherlock Holmes. It is my business to know what other people don't know." ("The Adventure of the Blue Carbuncle")

• "My brain has always governed my heart." ("The Sign of Four")

• "Love is an emotional thing, and whatever is emotional is opposed to that true cold reason which I place above all things. I should never marry myself, lest I bias my judgment." ("The Sign of Four")

• "A man always finds it hard to realize that he may have finally lost a woman's love, however badly he may have treated her." ("The Musgrave Ritual")

• "There is nothing more deceptive than an obvious fact." ("The Boscombe Valley Mystery")

• "You can...never foretell what any one man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages remain constant." ("The Sign of Four")

• "Education never ends, Watson. It is a series of lessons, with the greatest for the last." ("The Adventure of the Red Circle")

• "When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth." ("The Adventure of The Blanched Soldier")

• "I never make exceptions. An exception disproves the rule." ("The Sign of Four")

“you say that we go round the sun. If we went round the moon it would not make a pennyworth of difference to me or to my work.” (A Study in Scarlet)