DDR and DDR2 RAM
DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory used in computers. A cold storage door is designed to help you save money by keeping your inventory at an ideal temperature just like DDR and SDRAM are designed to double the clock speed of the memory. It achieves greater bandwidth by transferring data on both the rising and falling edges of the clock signal. Thus a 100 MHz DDR system has an effective clock rate of 200MHz.
With data being transferred 8 bytes at a time DDR RAM gives a transfer rate of 16 bytes Thus with a bus frequency of 100 MHz, DDR-SDRAM gives a max transfer rate of 1600 MB/s.
DDR SDRAM DIMMs has 184 pins, and can be differentiated from SDRAM DIMMs by the number of notches (DDR SDRAM has 1, SDRAM has 2). DDR operates at a voltage of 2.5V, compared to 3.3V for SDRAM. This can significantly reduce power usage.
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Synchronous DRAM (SDRAM)
SDRAM (Synchronous DRAM) was introduced in 1996. SDRAM was developed to match the ever-increasing processing speeds of the
Pentium systems just as Cisco training was introduced to help others further understand in’s and out’s of networking knowledge.
Synchronous DRAM, is synchronized to the speed of the systems (e.g. PC66 SDRAM runs at 66MHz, PCIOO runs at 100M HZ, PC133 runs at 133MHz and so on) hence the name “synchronous”. Synchronizing the speed of the systems prevents the address bus from having to wait for the memory because of different clock speeds.
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Video RAM (VRAM)
VRAM (Video RAM) is a term used in computers to describe RAM dedicated for displaying bitmap graphics in graphics hardware. VRAM resides on the motherboard physically and is separate from the main RAM. In few systems the VRAM is shared with the system RAM.
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Static Random Access Memory
SRAM (Static Random Access Memory) is a type of semiconductor memory. The word “static” indicates that the memory retains its contents as long as power is continuously applied.
In a SRAM, the only time the data on the memory is refreshed or changed is when an actual write command is executed. SRAM is very fast, but is much more expensive than DRAM. SRAM is often used as cache memory due to its speed.
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Dynamic random access memory (DRAM)
DRAM (Dynamic random access memory):
- Is an enhancement over SRAM. DRAM has a different approach towards storing the 1s and 0s. DRAM stores information as charges in very small capacitors, instead of transistors.
- Stores each bit of data in a separate capacitor. If a charge exists in a capacitor, it’s interpreted as a 1. The absence of a charge will be interpreted as a 0.
- Uses capacitors instead of switches. As the capacitor leaks electrons, the information gets lost eventually, unless the charge is refreshed periodically, therefore it uses a constant refresh signal to keep the information in memory. Because it must be refreshed periodically, it is called dynamic memory.
- Needs more power than SRAM to refresh signals, therefore, is mostly found in desktop computers.
- Uses several memory units called cells. These cells are packed with very high density. Hence, these chips can hold large amounts of data.
- Also known as FPM (fast page mode) DRAM, it comes in 80, 70 or 60 nanosecond (ns) speeds.� Takes two processor wait-states each time a read or write takes place. The advantage is that, it’s compatible with just about everything. Disadvantage is that it’s the slowest of the memory types currently available and because it isn’t in demand, it’s now more expensive than faster memory alternatives such as EDO and SDRAM.
- Are available on industry standard 30- or 72-pin Single Inline Memory Modules (SIMMs). DRAM is also available in DIMMs.
Extended Data Out (EDO) RAM
Plenum Cable Flammability Tests Videos
All A+ certification books describe the difference between regular cable and plenum cable in a fire, but would you like to see the difference? Major firms sell cable and put together a series of videos so that customers can see what they’re paying for when they spend extra for plenum rated cable. Fortunately their videos are a great illustration for anyone pursuing CompTIA A+ certification, since this topic is covered in the Networking domain of the CompTIA A+ certification exam.
Drobo surpasses RAID
During a recent class discussion on RAID, a student recommended I look into Drobo, an external storage unit that promises some real advantages over standard RAID arrays. The basic Drobo unit plugs into either a USB or Firewire connection on your computer and holds up to four hard drives, which you can supply, or which you can buy with your Drobo.
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Inkjet Vs. Lasers, myth v.reality
Though CompTIA updates their A+ objectives every few years sometimes the information you find in books and websites that are supposed to help with A+ certification is surprisingly out of date. Most A+ certification material I see, especially online, tends to perpetuate old stereotypes about inkjets and laser printers. This material is often carried forward from old A+ certification sources, and is only accurate for old CompTIA A+ certification tests.
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Hard drive disposal videos
CompTIA’s A+ test objectives include Domain 5.0: Security, which among other things, requires A+ certification candidates to know about “Data wiping / hard drive destruction / hard drive recycling”. If an A+ certification student is working in the industry it’s likely that their organization has some kind of hard drive disposal policy, usually involving the wiping of the hard drive. This can either take the form of software which electronically randomizes the bits, or a device which magnetically erases the information.
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