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About HARD DRIVE and RAM Memory

Last Updated September 23, 2005

Hard Drive: What Is It?
A hard drive is the main form of data storage on a personal computer. It is where your various programs and files reside.

How Do You Know What's Good?
The primary factor with a hard drive is capacity... that is, how much data it can hold.
Hard-drive capacity is measured in gigabytes (GB), with bigger being better.

Optional Terms to Know

Rotational Speed
If you are seeking high performance, then you also should consider a hard drive's rotational speed, measured in rotations per minute (RPM). The faster a hard drive rotates, the faster it can transfer data. In addition, some drives include special buffers or caches that can further increase the effective transfer rate. However, in a laptop, the faster the Rotational Speed the quicker it will consume the battery life.

What Can Fit Into 10 Gigabytes?
To give you an idea of what fits into 10 gigabytes of storage space, we've broken-out the storage requirements of programs and files that you might have on your hard disk. The total storage in the pie chart adds up to 10 gigabytes. However, today's hard drives typically store a multiple of 10 gigabytes, so multiply what you see here by the appropriate number for your needs.

Why is my Hard drive reported smaller than that in the specifications?
Computers running on Widows may appear to have a hard drive smaller than what is stated in the product's specifications, documentation, or what is stated on the box. Particullarly, windows reports smaller capacity in the Windows Explorer tool.
Example a 40Gigabyte Hard drive will be displayed as 37.27 GB (gigabytes) in Windows Explorer. Why?

Hard drives are described and advertised by manufacturers in terms of decimal (base 10) capacity.
In decimal notation, one megabyte (MB) is equal to 1,000,000 bytes, and one Gigabyte (GB) is equal to 1,000,000,000 bytes.

Windows and other programs use the binary (base 2) numbering system.
In the binary numbering system, one megabyte is equal to 1,048,576 bytes, and one gigabyte is equal to 1,073,741,824 bytes.
In layman terms:
A manufacturer will label the drive as 40Gb meaning 40Billion bytes.
The same Hard Drive will be reported in Windows as 37.25GB because in Windows Explorer it is computed as 40,000,000,000bytes divided by 1,073,741,824bytes equals 37.2528Gb

The decimal system is what we use in everyday life but Microsoft wants to be different...


A Hard Drive Primer
Appropriately named, hard disk drives (HDDs) contain within them hard metal disks, or platters, which are covered with a magnetic coating of rare earth alloys. As one of these platters spins, read-write (RW) heads travel in toward the platter's center and back out toward its edge to magnetize the surface of the disk. This allows binary zeroes and ones to be stored on the platters as data.

A drive's storage capacity determines how many platters are on the same spindle. While both sides of every platter have their own RW heads, these heads are all on arms that are parallel to each other (think of the teeth of a comb moving between thin, parallel spinning wheels).

The heads on all these arms are connected to the same electromagnetic actuator, or servo. This means that if the data your computer needs is on, say, the top platter's top surface, the head moving to read that data will result in all the heads moving to matching spots on their respective platters. Only the top head in our example would read data, however. That data is kept on the platters in concentric tracks, each of which is broken down into small areas called sectors. There's another spec of hard drives you might have encountered: cylinders. Cylinders are vertical arrangements of tracks located the same distance in toward the center on each platter.

To get all the aforementioned physical components of a drive to store and retrieve the maximum amount of data, engineers are continually advancing the respective technologies involved. Better media are being used for platters, and more accurate heads and servos are always being developed. This means more data can be squeezed into less space, and can be read more accurately

Latency refers here to the time a drive spends waiting for the correct sector of a platter to rotate beneath its respective head. Logically, the faster the disk spins, the shorter the wait time. Therefore a Laptop hard disk with a 7,200-rom rotational speed will offer a lower latency than a 4,200-rpm drive.

Average seek time refers to how long it takes an RW head to move to the correct position on a desired track. You'll find that seek time is approximately 12 milliseconds (ms) in laptop hard drives, while many desktop units achieve better times of less than 10 ms. Part of the reason for this speed lag in the portable form factor is that RW head positioning in laptops is more critical as a result of the smaller platters used in the drives

More Reading:
If you are interested to find out about File Systems: FAT, FAT32, FAT16, NTFS <click here>
For the Harddrive Fanatic <click here>


Memory: What Is It?
Memory is a type of temporary storage that holds the programs and data you are currently running. When you see the term "memory" by itself, it means the computer's main random-access memory (RAM), which is what this article covers. <click here>

RAM(Random Access Memory), generally is used to describe a computer's dynamic storage area, where raw data is made available to the CPU, and which serves as a conduit for processed data received from the CPU. Everything uses RAM and therefore everything from the Operating System to intensive 3D gaming benefits from the increased amount of RAM. The greater the memory, the better performance you'll experience when running multiple applications or working with larger files

How Do You Know What's Good?
The primary factor with memory is its capacity or how much data it can hold.
Memory capacity is measured in megabytes (MB) or gigabytes (GB), with bigger being better.

Memory Speed
If you are seeking high performance, then you also should consider the memory's speed, or how fast it can exchange data with the processor. This speed, which will be the same as the computer's front-side bus speed, is measured in megahertz (MHz), with faster being better. Different types of memory (SDRAM, DDR-SDRAM, and RDRAM) are distinguished mainly by the speeds they can handle.

Types of Memory
EDO MEMORY - Once considered cutting edge, EDO is simply FPM DRAM that is been slightly modified to modestly boost performance. The modification allows one read to begin before the last one has been completed, and the overlap can increase raw transfer speed by 20 percent.

SDRAM (Synchronous Dynamic Random Access Memory) has largely been superseded by DDR-SDRAM, but you still see SDRAM on some systems. For basic computing needs, you probably won't notice much of a performance difference between SDRAM and the faster DDR-SDRAM. But given DDR-SDRAM's popularity, the only reason to go with SDRAM is if it was the only choice on an otherwise desirable computer.

DDR1-SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory) is the dominant type of memory today. DDR refers to Double Data Rate, where data is sent both at the beginning and the end of each clock cycle, resulting in faster access speeds.

DDR SDRAM utilizes the existing SDRAM infrastructure and technology while doubling the nominal bandwidth available to systems. In plain English, imagine that PC133 SDRAM is like data going along a one way street. DDR SDRAM is like data going along a two lane highway, as DDR stands for Double Data Rate. What is this good for? Well, any application really. Everything uses RAM and therefore everything from the Operating System to intensive 3D gaming benefits from the increased speed of DDR SDRAM. DDR-SDRAM has another important improvement over PC133 SDRAM. Its voltage supply is only 2.5V, instead of 3.3V. This and the lower capacitances inside the memory chips lead to a significantly reduced power consumption, which makes DDR-SDRAM very attractive for notebooks.

DDR2 SODIMMS For notebook-pc's offer a number of improvements over the previous DDR1 generation memory solution. These include a space-saving form factor, low power consumption, improved thermal characteristics, and high bandwidth. All this results in greater performance per watt and improved battery life compared to other memory standards.

DDR2 notebook SODIMMS are rated at 1.8 Volts, which is nearly a full Volt (0.8V) lower than DDR1 SODIMMs and feature IC's based on the FBGA process. This means that notebooks with DDR2 modules require up to 65% less voltage than those running DDR400, thus improving battery life. Samsung, a leading semiconductor manufacturer, ran internal tests and showed that a notebook PC equipped with Samsung DDR2 memory lasted close to 10% longer before requiring recharging. Notebooks with DDR2 memory bring this goal a step closer as the extra 10% battery life can improve mobility and thus productivity

Note: DDR1 and DDR2 memory can not be used on the same DIMM slots due to an alignment change in the PCB.

DDR2 info and photo courtesy of Atty.Anton and LegitReviews <click here>

Want to Upgrade your RAM?
Try out this free software from Crucial.<click here>

How Much Memory Do You Need?
MEGABYTE - (MB) 1,048,576 bytes bytes (2 to the 20th power). A unit of quantity used to describe the capacity of memory and storage devices

Unlike processors and hard drives, where the technologies have come so far that "Basic" choices are good for most people, memory is an area where the budget-oriented choice 128 megabytes can cause problems. While it's possible to get by with this amount, we don't recommend it. We're not alone: Microsoft recommends at least 256 megabytes of memory for computers running Windows XP, as virtually all new computers do. As for the type of memory, DDR-SDRAM is the best choice here because of its value for the perfomance.

Frequently Asked Questions:
What do terms like "PC2700" and "DDR333" mean?

These terms indicate a combination of memory type and memory speed. For a variety of reasons, they are not user-friendly terms. What's it all mean? The PC133, DDR333, and DDR400 numbers are the front side bus speeds at which the RAM can be accessed. This equals MHz per cycle.

Think about it as a speed limit on DDR's two-lane highway.
The DDR333 highway is designed to support combined traffic speeds up to 333MHz (2 lanes traveling at 166MHz). While DDR400 memory allows traffic speeds up to 400MHz (2 lanes at 200MHz).

But wait, the RAM says it is PC-2700. What's that? PC- is a new naming standard for the speed of DDR memory. It's equivalent to the theoretical speed of the RAM.
DDR200 is PC1600 200Mhz 100Mhz Actual Clock Rate (1.6 GB/sec Throughput)
DDR266 is PC2100 266Mhz 133Mhz Actual Clock Rate (2.1 GB/sec Throughput)
DDR300 is PC2400 300Mhz 150Mhz Actual Clock Rate (2.4 GB/sec Throughput)
DDR333 is PC2700 333Mhz 166Mhz Actual Clock Rate (2.7 GB/sec Throughput)
DDR400 is PC3200 400Mhz 200Mhz Actual Clock Rate (3.2 GB/sec Throughput)

The new standard is PC3200 DDR Memory, which allows you to run a healthy 400 MHz FSB effectively and speeds up performance in systems that can use 400MHz DDR memory.

Where possible, ignore them and just focus on the memory's type and speed.

Our Take:
1. RAM Memory is Easily Upgradeable
2. RAM Memory Prices are going down as you read this article
3. RAM is the cheapest way to improve the performance of your Laptop
4. The More RAM and Better. It never hurts to have More RAM
5. If your notebook is under warranty, best to have the RAM upgraded by the Laptop vendor to avoid having the warranty voided.