How to Choose the Right MEMORY for your DIY PC computer

How to Choose the Right MEMORY for your computer
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In building your own DIY PC Computer, one of the undeniable necessary ingredients is MEMORY.

Be it a desktop, laptop, or handheld devices, knowingly or unknowingly, we come into usage of memory, be it volatile memory such as DRAM, SRAM or non-volatile memory such as ROM, flash memory.

Some common examples of non-volatile memory includes: CD-ROM, DVD-ROM, SD cards, and your typical thumbdrive. As for volatile memory, your computer memory will be a good example.

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Insights into the Computer Memory - What is DRAM ?
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The memory utilized in computers is commonly known as DRAM (Dynamic Random Access Memory)

The definition of DRAM according to Wikipedia, the free encyclopedia is as follows:

"Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory."

To make it simple, the DRAM is used by the computer to hold temporary instructions and data, hence facilitate fast access to stored instructions and data. It means that programs are loaded faster, running faster, with increase in efficiency and user experience.

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TECHNOLOGY TIMELINE
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Memory Technology has gone a long way as like computers, so it is cool to know the past history of DRAM.

YEAR INTRODUCED TECHNOLOGY SPEED LIMIT
1987 FPM 50ns
1995 EDO 50ns
1997 PC66 SDRAM 66MHz
1998 PC100 SDRAM 100MHz
1999 RDRAM 800MHz
1999/2000 PC133 SRAM 133MHz (VCM option)
2000 DDR SDRAM 266MHz
2001 DDR SDRAM 333MHz
2002 DDR SDRAM 434MHz
2003 DDR SDRAM 500MHz
2004 DDR2 SDRAM 533MHz
2005 DDR2 SDRAM 800MHz
2006 DDR2 SDRAM 667 - 800MHz
2007 DDR3 SDRAM 1066 - 1333MHz
2008 DDR3 SDRAM 1333 - 1600MHz


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How Much Memory Do I Need ?
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Based on different user requirements, different amount of workload is required of the computer, hence to enhance the efficiency, different memory configurations are also recommended as per below guidelines.

Extract from Kingston Technology website, the below is a summary of the baseline and recommended memory levels for different Operating Systems:

-->WINDOWS® VISTA
Requirements Entry Mainstream Performance High-end
Desktop 1GB – 3GB 2GB – 4GB 2GB – 8GB* 4GB to System max**
Notebook 1GB – 3GB 2GB – 4GB 2GB – 8GB* 4GB to System ma

-->WINDOWS® XP PROFESSIONAL and HOME
Baseline: 128MB - 256MB
Optimal: 512MB - 1GB

-->WINDOWS® 2000 PROFESSIONAL
Baseline: 128MB - 256MB
Optimal: 512MB - 1GB

-->WINDOWS® 98
Baseline: 64MB - 128MB
Optimal: 128MB - 256MB

-->LINUX
Baseline: 512MB - 1GB
Optimal: 1GB - 2GB

-->MACINTOSH™ OS X
Baseline: 512MB - 1GB
Optimal: 1GB - 2GB

-->WINDOWS® 2003 SERVER
Baseline: 2GB
Optimal: 4GB - 64GB


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UNDERSTANDING DRAM SPECIFICATIONS
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By and large, the most common DRAM memory seen for computers nowadays are commonly known as DIMMs(Dual In-line Memory Modules). They install vertically into expansion sockets, and come in various form factors and are specific to different DRAM technologies.

DIMMs transfer 64 bits of data at a time and are typically used in computer configurations that support a 64-bit or wider memory bus. However, the distinct difference between desktop and notebook DRAM is in the number of pins of the DIMM chip. A desktop computer nowadays uses a 240-pin DIMM while a notebook uses a smaller 200-pin SODIMM (Small Outline DIMM).

When we buy memory either online or at a local retailer, we are always presented with info in the following manner:

Eg:

4GB 4096MB-1600MHz DDR3 PC12800 240p DIMM



1GB 1024MB-667MHz DDR2-667 PC2-5300, 200p SODIMM

What exactly does all these numbers mean?

1) XX GB : Refers to the amount of actual memory. 1 GB = 1024 MB, and the more memory available, the more data that can be stored and the faster the performance.
2) DDR2/3 : Indicates the generation of DDR SDRAM (DOUBLE DATA RATE SYNCHRONOUS DRAM), with each improved generation, we are seeing higher memory bus clock rate, which improves the data rate.
2) DDR2-xxx: Denotes data transfer rate, and describes raw DDR chips
3) PC2-xxxx: Denotes theoretical bandwidth. Bandwidth is calculated by taking transfers per second and multiplying by eight. This is because DDR2 memory modules transfer data on a bus that is 64 data bits wide, and since a byte comprises 8 bits, this equates to 8 bytes of data per transfer. Eg: DDR2-667 --> 667 * 8 = 5300

Standard name	Memory clock	Cycle time	I/O Bus clock	Data transfers per second	Module name	Peak transfer rate
DDR2-400	100 MHz	10 ns	200 MHz	400 Million	PC2-3200	3200 MB/s
DDR2-533	133 MHz	7.5 ns	266 MHz	533 Million	PC2-4200 PC2-43001	4266 MB/s
DDR2-667	166 MHz	6 ns	333 MHz	667 Million	PC2-5300 PC2-54001	5333 MB/s
DDR2-800	200 MHz	5 ns	400 MHz	800 Million	PC2-6400	6400 MB/s
DDR2-1066	266 MHz	3.75 ns	533 MHz	1066 Million	PC2-8500 PC2-86001	8533 MB/s

Standard name	Memory clock	Cycle time	I/O Bus clock	Data transfers per second	Module name	Peak transfer rate
DDR3-800	100 MHz	10 ns	400 MHz	800 Million	PC3-6400	6400 MB/s
DDR3-1066	133 MHz	7.5 ns	533 MHz	1066 Million	PC3-8500	8533 MB/s
DDR3-1333	166 MHz	6 ns	667 MHz	1333 Million	PC3-10600	10667 MB/s
DDR3-1600	200 MHz	5 ns	800 MHz	1600 Million	PC3-12800	12800 MB/s

Note: Although higher memory is always better, you also need to check other factors such as the memory bus clock rate versus the CPU clock rate, if the CPU cannot transfer data as fast as your memory chip, it would practically be a waste of money to buy something that is overspec. For example, your CPU runs at 800MHz, but the memory is running at 1600MHz, so the overall data transfer rate is still at 800MHz maximum. Get the picture? It is okay to be underspec, but meaningless and costly to be overspec.

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Installing your Memory Chips
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In building your own DIY PC, after installing your CPU, and motherboard, the next item will be your memory chips. You should spend some time planning and researching on memory which is compatible with the new CPU and motherboard you have installed to bring out the best overall performance. To install the RAM modules, you need to unfasten the clips located on each side of the memory slot. Align the RAM module in the socket, such as to match the indent located on the memory chip and the memory slot, for the right facing direction. Push down on the memory module until both clips refasten and a click sound is heard. To change memory, simply press down the both clips at the same time, and the RAM will come out easily.

TIP: Start adding RAM at the slot labeled “Bank 0” or “DIMM 1”. If you don’t, the system will think there is no memory available and wont boot.

TIP:For newer systems supporting hyper treading technology, you are encouraged to use the dual channel memory functionality by placing 2 sticks of the same memory on alternate slots (i.e.: slot 1 & 3 or Slot 2 & 4, often differentiated by color as well. ) This has been proven to enhance the performance as well.


For a better illustration, I have embedded a video to show you how you can install the computer memory easily.

With that i end off with a High Note: Have Fun Building Your Own DIY PC Computer !!