Hard Drive Read / Write Head Presentation
When someone mentions a hard drives “Heads,” they are referred to the electromagnetic instrument that writes magnetic “data” to the platters of hard drive. In this presentation I will discuss the history of read write heads and explain how they work. I will refer to the read write heads of a hard drive as heads for the remainder of the presentation.
IBM invented hard drives in 1956 for an accounting machine named the IBM 350. This was the machine that introduced disk storage to the world. It was bigger than most modern day filing cabinets. It had heads bigger than someone’s arms. Today hard drives are the size of the carrying handle for the first drive.
The first modern heads for a hard drive were introduced in the 90’s. They were known as the MR head or Magneto Resistive head. These were the heads that everyone refers to when they say,” my old hard drives never had any problems, in fact they still work today.” These heads were farther away from the platter than a hard drive manufactured today. They peaked out around the 30 GB capacity and were much slower than a modern hard drive.
After the MR head came the AMR head, which is short for, Anisotropic Magneto Resistive head. This head increased hard drive capacity by 100% a year till it reached its peak. In the year 2000 the GMR heads, short for Giant Magneto Resistive, were introduced. These heads were notorious for being very unstable. They did provide a big increase in capacity and speed at the cost of reliability.
Seagate introduced the latest breakthrough in hard drive head design in 2005. This head is known as the TMR head, short for Tunneling Magneto Resistive. This new head has a component that controls the temperature in the head so that it maintains the same shape throughout its use. By mid 2006 most other drive manufacturers adopted this form of head.
All hard drives heads have a similar role in the functions of a hard drive. They must convert an electrical signal sent by the motherboard into a magnetic signal to be encoded on the platters of the drive. Then they must perform this operation backwards to access the data stored on the platters. Early head designs had one component, which handled both the writing and reading. This led to many compromises, which only allowed for a very limited speed in these early drives. Modern drive heads have one component that controls the writing of data and another component that does the reading of the data. This allows for each component to be super tuned, which allows for much greater speed and capacity.
The most common component to fail besides the PCB is the hard drives head assembly. Some hard drives have as many as twenty heads all mounted on the same assembly. This makes data recovery extremely difficult. The most notorious drives for head failure are the 500 GB hard drives. They drives have four platters which means they have 8 heads in the assembly. This makes recovery extremely difficult when a head transplant is needed.
Modern Drives achieve their large capacities and high speed by moving the head closer and closer to the platter. This is because they encode weaker magnetic information on to the platters. Weaker signals can be packed tighter together than the stronger signals of older hard drives. The heads must come closer and closer to be able to pick up this weakened magnetic signal. To keep the heads from hitting the platters hard drives have a layer of air called the “Air Bearing” This air bearing keeps the heads from hitting the platters during normal operation. Even with the air bearing, modern heads are so close to the platter that a head crash is inevitable.
The next breakthrough in head technology is being developed as I write this. Engineers are replacing the conventional magnetic read write heads with futuristic lasers. In the future laser hard drives will be 100 times faster and can stored 100 times more information than hard drives today. They will also be much more reliable because they will not suffer for head crashes.
Computer Based Associates leads the industry when it comes to head replacement. We have successfully replaced heads from all the major hard drive manufactures. Head damage is usually indicated by a clicking or scratching noise coming from inside the hard drive. If you hear your hard drives start to click, stop using it and send it to us immediately. Call Frank at (305) 228-6163 if you have any questions about the read write heads of a drive.