Memory, Misty or Not

Lack of memory is a pain. Personally it is inconvenient. On a computer it is a real pain. But figuring it out can be sort of fun, getting your fingers dirty in the inner bowels of the machine.

The machine in this case is the Fujitsu Lifebook P1630

     http://www.ruggedpcreview.com/3_notebooks_fujitsu_1630.html

I've learned a lot of new jargon. For example:

2GB DDR2 667MHz PC2-5300 Memory Upgrade for Fujitsu-Siemens LifeBook P Series P1630. 1.8v 200-pin Non-Parity Un-Buffered


is translated as follows:

2GB	Short answer: Two billion bytes of Random Access Memory (RAM) Long answer: Approximately. Watch this space...
DDR2	One of at least three electrical forms of RAM, operating at 1.8 volts http://www.brighthub.com/computing/hardware/articles/12461.aspx Double Data Rate Synchronous Dynamic Random Access Memory interface. http://en.wikipedia.org/wiki/DDR2_SDRAM In addition to double pumping the data bus as in DDR SDRAM (transferring data on the rising and falling edges of the bus clock signal), DDR2 allows higher bus speed and requires lower power by running the internal clock at half the speed of the data bus. You cannot substitute one for the other for at least two reasons: the voltages are different the notch in the chip is different
667MHz	The clock rate (sample rate) for the RAM
SDRAM	Synchronous Dynamic Random Access Memory (SDRAM) is Dynamic Random Access Memory (DRAM) that is synchronized with the system bus. http://en.wikipedia.org/wiki/Synchronous_dynamic_random_access_memory Classic DRAM has an asynchronous interface, which means that it responds as quickly as possible to changes in control inputs. SDRAM has a synchronous interface, meaning that it waits for a clock signal before responding to control inputs and is therefore synchronized with the computer's system bus. The clock is used to drive an internal finite state machine that pipelines incoming instructions. This allows the chip to have a more complex pattern of operation than an asynchronous DRAM, enabling higher speeds. Pipelining means that the chip can accept a new instruction before it has finished processing the previous one.
PC2-5300	PC2-xxxx denotes theoretical bandwidth.
1.8v	This refers to the voltage applied to the RAM. DDR3 operates at 1.5, so the voltage difference is one of the reasons the various DDR variations are not compatible.
200 Pin	(as distinguished from 240 pin). These are the number of connections on the edge of the RAM. http://reviews.cnet.com/ram-memory/?filter=500056_112956_  Desktop computers use 240 pin RAM, while laptops use 200 pin RAM.
Non-Parity (Non-ECC)	Parity refers to having an extra data byte for ECC (Error correction code) http://en.wikipedia.org/wiki/RAM_parity http://en.wikipedia.org/wiki/Dynamic_random_access_memory#Errors_and_error_correction
Un-buffered	http://en.wikipedia.org/wiki/Registered_memory Registered (also called buffered) memory modules have a register between the SDRAM modules and the system's memory controller. They place less electrical load on the memory controller and allow single systems to remain stable with more memory modules than they would have otherwise. Registered memory is more expensive because of the additional components, so it is usually found only in applications where the need for scalability and stability outweighs the need for a low price (servers, for example). Although most server-grade memory modules are both ECC and registered, there are registered non-ECC modules and non-registered ECC modules. There is a performance penalty for using registered memory. Each read or write is buffered for one cycle between the memory bus and the DRAM, so the registered RAM can be thought of as running  one clock cycle "behind" an equivalent unregistered DRAM.

I've built a spreadsheet that calculates memory usage  based on the free command. I set a base configuration of kernel, operating system, and GUI and record the output of free. The usage is the sum of the used column entries, comprising
    Mem:
    -/+ buffers/cache:
    Swap:

I then load (or unload) a single program. Again, the usage is the sum of the used column entries. The usage of the program is the difference in the original usage and the new usage.

In my present setup (Linux 2.6.37.1-1.2-desktop kernel, openSUSE 11.4, KDE 4.6) I have 1 GB of RAM and 2 GB of Disk Swap.

The results are variable. They depend on what other apps have already loaded common libraries. They also depend on activity since the system moves stuff from main memory to cache to swap depending on what apps and associated files are in demand. For example, on one app whenever you type something the usage jumps to 16 MB, but wait a few seconds without further activity and it settles back out at 6MB.

With those caveats, the following shows representative usage:

• With minimal desktop (Firefox, Basket, konqueror, and kontact)  40 MB free (1.3GB used)
• Firefox is a memory hog: 122MB
• Konqueror uses 78 MB.
• GnuCash uses 60MB.
• The Oracle VirtualBox platform uses 48MB.
• Baskets uses 25 MB.
• Kontact uses 7 MB.
• But then start Windows in the VBox: it immediately gobbles 506 MB with no applications visibly running.
• Start TurboTax: another 10 MB.

Suffice it to say we need to get more RAM.