Unit 4:"Different types of memory and memory modules available."1. The differences between memory types:A. DDRDDR (Double Data Rate) memory is the next generation SDRAM (Synchronous DRAM). DDR is synchronous with the system clock. The big difference between DDR and SDRAM memory is that DDR reads data on both the rising and falling edges of the clock signal. SDRAM only carries information on the rising edge of a signal. Basically this allows the DDR module to transfer data twice as fast as SDRAM. Example; instead of a data rate of 133MHz, DDR memory transfers data at 266MHz, twice as fast.
DDR modules use motherboard system designs similar to those used by SDRAM. DDR is not backward compatible with SDRAM-designed motherboards. DDR memory supports both Non-parity, 'regular' memory, containing exactly one bit of memory for every bit of data to be stored. And ECC (error correction code), using more than one bit of memory.
B. DDR3DDR3 (Double Data Rate three) the third generation and most advanced Double Data Rate Synchronous Dynamic Random Access Memory. By offering reduced power consumption, a doubled pre-fetch buffer and also offers more bandwidth because of its increased clock rate.
C. RDRAMRDRAM (Rambus Memory) is a revolutionary step from SDRAM. RDRAM sends less information on the data bus (18 bits wide as opposed to the standard 32 or 64 bits), but it sends data more frequently. It also reads data on both the rising and falling edges of the clock signal, as DDR does. As a result, RDRAM is able to achieve effective data transfer speeds of 800MHz and higher.
2. The differences between parity (ECC) and non-parity memory.
A. ECC (Error-Correcting Code) Memory:Rarely found in home PCs, ECC is memory that tests the accuracy of data moving in and out and is able to detect and correct some errors without user intervention. These small errors are normally caused by cosmic rays. ECC memory is only really beneficial if a person is going to be processing massive amounts of data (like a server does) and all data needs to be 100% accurate. ECC memory is not normally needed for home systems, but is commonly used in server computers.
B. Non-Parity Memory (Non-ECC):Non-ECC is recommended for home and office desktop PCs. The biggest advantage that non-ECC memory offers to the consumer is an increase in speed over any ECC equivalent. Non-ECC is ideal for 99% of computers.
3. The differences of Registered Memory, Un-buffed, and Buffed Memory and when to use them;A.Registered memory:Registered memory contains buffers that take care of signal distribution to all DRAM on a DIMM. Buffers take one full clock cycle (2 DDR clock cycles) to buffer the control and address signals Registered memory has a higher capacity than un-buffered memory. Buffering increases the reliability of high-speed data access which is critical for server operations.
Registered modules are only used in Servers and Mission Critical systems where reliability is crucial (where a lot of large data is being moved). Regular home users and performance users will not get any benefits from registered memory and might actually see a slight decline due to the higher capacity of the buffering.
B.Un-buffered memory:Un-buffered memory is memory where the memory controller module drives the memory directly, instead of using a store-and-forward system like registered memory. Some systems do not support un-buffered memory, others require un-buffered memory and many more give you the option to use un-buffered or registered memory. The use of un-buffered memory is reasonable for gaming systems. It is not recommended for server-class systems. Un-buffered memory is also known as 'unregistered memory'.
C.Buffered memory:Buffered memory uses a Buffer chip to boost the clock signal sent across the memory module so that the clock signal is seen as a clean, sharp signal across the entire module. It eliminates chances of memory errors in data sent or retrieved from memory. It is commonly used in larger capacity EDO (Extended Data-Out) modules. Buffered modules have a different keyway in the contact edge and can only be used when the board supports buffered modules. Unlike registered modules, it is not interchangeable with un-buffered modules.
4. The differences between IDE and SCSI;A. IDEIDE (Integrated Drive Electronics) is a standard electronic interface used between a computer motherboard's data paths and the computer's disk storage devices. The IDE interface is based on the ISA (Industry Standard Architecture) 16-bit bus standard, but it is also used in computers that use other bus standards. Most computers sold today use an enhanced version of IDE called EIDE (Enhanced Integrated Drive Electronics). In today's computers, the IDE controller is often built into the motherboard.
B. SCSI;SCSI (Small Computer System Interface) is a set of interfaces that allow personal computers to communicate with different hardware such as; disk drives, tape drives, CD-ROM drives, printers and scanners faster and more flexibly than previous interfaces. The primary objective for SCSI interface is to provide host computers with independence from proprietary devices.
5. The differences between SATA, PATA, and ATA;A. SATA: is an IDE (integrated development environment) standard for connecting devices like optical drives and hard drives to the motherboard. The term SATA generally refers to the types of cables and connections that follow this standard.
SATA cables are long, thin, 7-pin cables. One end plugs into a port on the motherboard, usually labeled SATA, and the other into the back of a storage device like a hard drive.
Serial ATA replaces Parallel ATA as the IDE standard of choice for connecting storage devices inside of a computer. SATA storage devices can transmit data to and from the rest of the computer over twice as fast as an otherwise similar PATA device.
B. PATA: Parallel ATA (PATA) is an IDE standard for connecting storage devices like hard drives and optical drives to the motherboard. PATA generally refers to the types of cables and connections that follow this standard.
PATA cables are long, flat cables with 40-pin connectors (in a 20x2 matrix) on either side of the cable. One end plugs into a port on the motherboard, usually labeled IDE, and the other into the back of a storage device like a hard drive. Some PATA cables have an additional connector midway through the cable for connecting yet another storage device.
PATA cables come in 40-wire or 80-wire designs. Most modern storage devices require the use of the more capable 80-wire PATA cable to meet certain speed requirements. Both types of PATA cables have 40-pins and look nearly identical so telling them apart can be difficult. Usually though, the connectors on an 80-wire PATA cable will be black, gray and blue while the connectors on a 40-wire cable will only be black.
C. ATA: The ATA standard allows you to connect storage peripherals directly with the motherboard thanks to a ribbon cable, which is generally made up of 40 parallel wires and three connectors (usually a blue connector for the motherboard and a black connector and a grey connector for the two storage peripherals).
On the cable, one of the peripherals must be declared the master cable and the other the slave. It is understood that the far connector (black) is reserved for the master peripheral and the middle connector (grey) for the slave peripheral. A mode called cable select (abbreviated as CS or C/S) allows you to automatically define the master and slave peripherals as long as the computer's BIOS supports this functionality.
Even though PATA and SATA are both IDE standards, PATA (formally ATA) cables and connectors are often referred to simply as IDE cables and connectors.
6. The explanation for hard drive partitioning and the benefits;Disk partitioning divides the data storage space of a hard disk into separate areas referred to as 'partitions'. Partitions are usually created when the hard disk is first being prepared for usage. Once a disk is divided into partitions, directories and files may be stored on them. Later changes on the computer and operating system often an administrator or power user will be faced with the need to resize partitions, create new partitions in the unallocated space and sometimes even undelete partitions that were previously removed or deleted.
Benefits:1. It may reduce the time required to perform file system checks (both upon boot up and when doing a manual check), because these checks can be done in parallel. (By the way, NEVER run a check on a mounted file system!!! You will almost certainly regret what happens to it. The exception to this is if the file system is mounted read-only, in which case it is safe to do so.) File system checks are a lot easier to do on a system with multiple partitions. Example; if I knew my home partition had a problem; I could simply unmount it, perform a file system check and then remount the repaired file system.
2. Multiple partitions, you can, mount one or more of your partitions as read-only.
3. The most important benefit that partitioning provides is protection of your file systems. If something should happen to a file system (either through user error or system failure), on a partitioned system you would probably only lose files on a single file system. On a non-partitioned system, you would probably lose them on all file systems.
7. Problems created by fragmentation;8. Describe how your customer would fix a fragmented hard drive at home.
1. Before running the defragment program, first save all work and exit all programs. Then, to ensure that the defragment utility itself runs quickly, disable the screen saver.
2.Using the mouse, right click on any part of the desktop that is not an icon or a tool bar, left click on Properties, the Screen Saver Tab, the arrow in the box under screen saver, scroll to None and click on Apply, then OK.
(Failure to disable the screen saver causes the defragment utility to start again each time the screen saver appears, prolonging the procedure).
3.Left click on Start, Programs, Accessories, System Tools, and Disk Defragmenter. When asked which drive to defragment, select All Hard Drives if the computer has more than one. If the computer only has one drive, select C. In Windows 95, click OK. Windows will examine the hard drive to determine what percent is defragmented. Even if told, "You do not need to defragment this drive now," continue anyway. (A drive that is fragmented only 1 percent can slow the system).
4.Click on Advanced and make sure that there is no checkmark in the box labeled Check Drive for Errors, then click OK and Start. For Windows 98 and Windows ME, click on Settings (again, make sure there is no check in the box labeled Check Drive for Errors), then click OK.
Even if the screen saver has been disabled, there is still a chance that the defragmentation process will reset itself and begin from zero. This is indicated when the message "Drive's Contents Changed" appears before the fragmentation is complete. If this happens, take a break and let the utility program run again. Eventually it will run all the way through. After the defragmenting utility runs, return the screen saver to its original settings.
References:Schmidt, C. A. (2008). "The Complete A+ Guide to PC Repair". Fourth Edition. Boston: Addison-Wesley. Chapters 6 & 7.
(1998 - 2009). "Memory" PC Tech Guide. Retrieved October 11, 2009, from Web site: http://www.pctechguide.com/(2004 - 2010). "Different Memory Types". Velocity Guide. Retrieved October 12, 2009, from Web site: www.velocityguide.comLister, John (2009). "What is Buffered Memory?" Wise Geek. Visited October 12, 2009 at Web site: www.wisegeek.com/what-is-buffered-memory.htm