ECE1F08S2:Advancements in Data Storage Devices
From Professor Kriehn
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Advancements in Data Storage Devices
ABSTRACT
Technology is advancing very fast. As the years go by, old technology goes out of date while new technology replaces it. A perfect example of this is data storage devices such as floppy disks. Now we have flash memory devices that are used instead of floppy devices. As technology advanced, improvements were made, and new devices were created that are faster, more reliable, and sufficient.
INTRODUCTION
All data storage devices are removable, portable, written, and read. Their sole purpose is to carry data that you may wish to save or transfer to another computer, camera, or something of the sort that is compatible with it. They are not permanent so the data can be erased and written over again.
Floppy is where it began. There were many different types of floppy disks because it was improved and improved making the design more efficient and which also affected its size. Sometime after, Zip Disks were created. This was a bigger type of floppy disk which was a very huge improvement. It was not like the basic type of floppy, thus giving it a new name.
Shortly after the Zip Disk was created, Compact Disks, or CDs as they are called, came to the market. It was much more efficient, and looked better which ruined the business for the zip disk. Different types of CDs soon were made. They had different purposes, some were the same. CDs were a big improvement.
Last, Flash Memory Devices have come to the market. There are many different types for just about every electronic device. They come in cards, sticks, and chips and work with just about anything. They are the most commonly used storage device right now.
BACKGROUND INFORMATION
In 1971, IBM invented the first floppy disk. Known as the “memory disk” then, the floppy disk inherited its name because its first models were flexible. It was first created as an 8 inch disk. After being improved greatly it finally made it down to 5.25 inches, and then finally a 3.25 inch disk.
FLOPPY DISKS
Both the 5.25 inch and 3.25 inch floppy disks were used commonly. The 3.25 inch floppy disk was used more, though, but both were still in use. The 5.25 inch floppy was larger and couldn’t hold as much space as the 3.25 inch one could so it was preferred to have the 3.25 inch.
The floppy disks were a flexible thing disk that was encased for protection. They were both written and read magnetically. The 5.25 inch floppy was encased by a flexible plastic envelope while the 3.25 inch floppy was encased by a rigid case. (2) The 5.25 inch floppy disk also known as the Double Density Disk and can be identified with a label “DD” on it. Its capacity was 720kb. The 3.25 floppy disk was known as the High Density Disk and was labeled with a “HD” on the case and its capacity was 1.44Mb. (6)
In order to use a floppy disk, it must first be formatted, which basically divides it into tracks and sectors. Tracks are rings that go around the disk while sectors are sections that look like slices of pie. After the floppy disk has been formatted, data can now be written on it. The 3.25 inch floppy disk was a fixed format of the following: (4)
• 135 tracks per inch
• 80 tracks per slide
• 18 sectors per track
• 512 bytes per sector
• 360 rpm
Floppy disks are coated with iron oxide which is a ferromagnetic material. Using magnetic fields, the floppy disk drives can magnetize the disks to add data to it. The procedure that a drive writes to a floppy disk is as follows: (2)
• There are two motors in the drive. The first motor spins the floppy disk.
• The second motor matches the spacing between the tracks.
• The read/write head then stops at the track it looks for.
• It checks if everything is correct there.
• It adds an erase coil.
• Finally it adds data by magnetizing the particles embedded into the surface and aligns them according to the data representation.
• The disk stops spinning and waits for the next command.
The disk coding is written in binary, and by aligning the particles correctly, the binary code is then created. (6) The time for the second motor to match the spacing between the tracks is called the “access time” which is the reason that floppy disks were not very fast. (2)
ZIP DISKS
Created by the Iomega Corporation in 1995, Zip Disks were a huge improvement to the floppy disks. Its size wasn’t any different; it was still 3.5 inches. The Zip disk was pretty much the same thing, but with a few changes, the capacity increased greatly and the speed increased, as well. (4)
The Zip Disk was created with a much higher quality of magnetic coating than the floppy disks used. Because of this, the disk was able to pack thousands of tracks per square inch compared to the few hundred of the floppy disk. This makes the read/write head of the Zip Drive smaller which also increases the speed that it can move. (4)
When formatting the Zip Disk, it is not given a fixed number of sectors and tracks like the floppy disk are. This allows the Zip Disk to hold a huge amount of data. There are two different types of Zip Disks: the 100Mb disk and the 250Mb disk. (4) Basically the Zip Disk is a more refined version of the floppy. Their physical appearance were very similar.
COMPACT DISKS
The Compact Disk, or CD, as everyone calls it, was a big improvement for technology. Everybody used CDs for many different reasons. Music is the most common, but it is also commonly used for data, as well.
The CD is 12 cm in diameter with a hole in the center of it. The hole is 15 mm in diameter. The CD is 1.2 mm thick. (3) The disk has only one track on it, and is spiraled outward, but this one track alone is able to carry 783,216,000 bytes of information on it. (1) The total length of the track is almost 3 minutes long. (3)
The CD is made of 4 layers. The part with the information on it is called the substrate layer. Here, the data is stored with the combination of pits and lands. Pits are molds on the substrate layer, and lands are area between the pits. With different changes in the pits and lands, a frequency is created, which is then read as the binary code. Land segments are read as 0, while changing between lands and pits are read as 1. There are about 2 billion pits on the surface of the CD. (3)
Above the substrate layer lies the reflective layer. This is what is used to send the light back out so that lasers can read the substrate layer. The reflective layer is made of aluminum and only serves that one purpose. (3)
Above the reflective layer lies the protective layer. It is made up from lacquer and serves only to keep dust or damaging particles from interfering with the substrate layer. (3)
The top of the substrate layer is the label. It is the part that you may write on. You do not need to worry if this side is scratched or dirty or interfered with in any way, so long as the damage is not deep. Scratches on the bottom of the CD where the data lies, is not much to worry about if it is a radial scratch. If it is a circumferential scratch, then it will interfere and confuse the CD drive. These scratches can be fixed by polishing the CD, though. (3)
The CD is read by a laser beam. The properties of the laser beam are as follows:
• 780 nm wave
• Moves in radial direction
• Emits light
• Scans for intensity of reflected light
• Analyzes the different light from both lands and pits
The speed of the CD started at 15 kb/s. This is labeled as 1X. With improvement, the CD was able to get to 52X which is really fast compared to previous data storage devices.
FLASH MEMORY DEVICES
Flash memory devices are known as solid state storage devices. Everything in it is electronic instead of mechanic which means that nothing in it moves. It makes no noise so it is better than anything before it. It is more of like a hard drive than RAM. The flash memory devices have made it much easier and faster to store and transfer information. These devices are much faster than previous storage devices and are small and lighter. (5)
Flash memory devices are a type of EEPROM chip. EEPROM is an acronym for Electronically Erasable Programmable Read Only Memory. It is made up of two transistors separated by a thin oxide layer. One is called the Floating Gate and the other is called the Control Gate. With the Control Gate in place, the cell will have a value of 1, and the process to change it to a 0 is called Fowler-Nordheim tunneling. (5)
Tunneling is used to alter the placement of electrons in the Floating Gate. It takes 10 to 13 volts in order to do this. The power supply comes from the column, or Bitline, and it enters the Floating Gate and drains to the ground. (5)
Excited electrons are pushed through the Floating Gate and trapped on the other side of the oxide layer. This gives a negative charge which also acts as a barrier. The cell sensors monitor the level of charge through the Floating Gate. If the charge is above 50 percent, then it is read as 1. If it is under 50 percent then it is read as 0. A blank EEPROM means the entire cell is 1. (5)
The design of flash memory devices is simple. Most are cards. Some are chips and others are sticks. The Plane Electrode is connected to a flash-memory chip by bonding wires. That is then embedded in a Resin through a technique called Over-Molded Thin Packaging (OMTP). That is then glued to the base card, which just makes it look like a card. There is a notch in the left or right corner. This is just information for the reader to know if 5 volts should be applied, or if 3.3 volts should be applied.
APPLICATIONS
This technology has been applied and is still being applied to almost everything right now. The floppy disks and Zip disks were only for transferring or storing data because their capacity was limited. Once the CDs came out there were more application possibilities due to the vast increase in data storage capacity. They were also used to store data and transfer, but in society, they are also used for music and videos. Sound uses a large amount of data for storage. Before CDs the only media used to record sound electronically in a consumer market was cassette tapes. When CDs hit the market they were an instant success due to the huge breakthrough in data storage that allowed for clear clean sound recording and playback. CDs allowed computer programs to become much larger. Before Cds computer programs had to be compact because it was not feasible to put a program on 20+ floppy disks. CDs immediately increased this limitation so that the limiting factor was now the computer hardware and not the portable memory storage. CDs evolved to create DVDs which allow data storage up to DVD 5 which has a capacity of 4.7 GB. DVDs took the market in the movie industry creating a new high quality playback and were more durable than cassette tapes. Currently CDs and DVDs are the main portable storage medias due to their capacity, reliability and low cost to manufacture.
With flash memory now, storing pictures in the camera is now possible. It is rare that you are limited to how many photos you take. Also, there are many mp3 players that use flash memory, and also USB flash drives use flash memory. Other devices that use flash memory devices are cell phones, dvd players, video games, and digital frames. Anything that could story data or can be run off of stored data is able to use flash memory devices. Flash memory has become inexpensive and is now seen throughout the entire consumer electronic market. Flash memory is unique in that all data is stored electronically and not physically like with CDs and DVDs. The electronic storage allows the media to be written to and rewritten almost without limits.
It is hard to picture what might be the next thing, but as for now, only improvements can be made. Such improvements can be bigger storage and faster transfers. Maybe, a universal data storage device could be created.
LIMITATIONS
Floppy drives were very limited when it came to their purpose. They could only go so fast, and they were pretty big because they could only be minimized so small to still be read and contain enough room for data.
Zip Disks were pretty much the same as floppy disks. With type of media there was a limited in storage capacity due the the magnetic media used on the rotating disk. That’s why CDs were created, but at first, ZIP Disks were a little more reliable than CDs.
CDs and DVDs are used for most of our inexpensive protable media storage. They could be very small, as you seen in some video games such as the PSP. But the speed is limited because the disks musk turn faster and faster in order to increase the read speed.
Flash memory is not limited at this time except for price. Flash memory is expensive and it would be very costly to have 850 GB of flash memory. It is being applied to everything, and can do everything. You can watch a movie off of flash memory devices now, so soon DVDs and CDs may become extinct as the storage devices before them have. At this time CDs and DVDs are used because the disk is very inexpensive. Until the price of flash memory decreases, CDs and DVDs will still be in the consumer market place.
CONCLUSIONS
Technology has advanced so much in the years. It has been made possible to carry data around with people. At first it was only stored data in a device. Now, the data could be used right off the device, sometimes the device can also use the data it holds. Everything started with floppy, improved to Zip Disk, converted to CDs, and finally is switching over to flash memory devices. With the rate of advancement in technology, a universal device is possible in the future.
REFERENCES
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5. Tyson, Jeff. "How Flash Memory Works." 30 August 2000. HowStuffWorks.com. <http://electronics.howstuffworks.com/flash-memory.htm> 03 November 2008.
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