Category Archives: Memory


Secure Digital High Capacity, or SDHC, is a format implemented on flash memory cards. It was developed by Toshiba, SanDisk and Matsushita for portable use in most carry-around electronic devices, like cellular phones, digital cameras, PDAs, video game consoles and GPS receivers. SDHC cards have capacities that range from 4GB to 32 GB, in contrast to standard SD cards’ 8 MB to 4 GB.

The SDHC format has been known to perform well with the newer gadgets. It looks just like normal SC cards and often confuses most users. SDHC, however, has compatibility issues with the older devices.

SDHC cards require SDHC firmware — a device not found in older electronic devices. Also, the new format is not backwards compatible with SD format host devices. To be sure, look for the SDHC logo on cards and electronic devices you plan to purchase.

New Standard Created by SDHC

SDHC cards are market leaders when it comes to digital photography because of the way it preserves image integrity and because it guarantees minimum performance floors. The image compression and the quality of the memory in SDHC cards are also praised by the video industry. In fact, SDHC cards created a new rating for minimum data transfer directed towards both high-capacity and standard cards.

This new Speed Class enables the host product to check the fragmented state of the card and to measure the writing speed in every part of that card. The same host can also conclude where it could write the data depending on the speed requirement.

MiniSHDC and MicroSHDC

  • Mini SDHC was developed right after the miniSD for more speed class options and storage power with smaller space occupied. This was mainly developed for smaller and newer cellular phones. It can be used with miniSD adapters to share digital content with devices accommodating SD cards.
  • The microSDHC cards are known as the smallest memory cards which are ideal for media-rich files like videos, music and high-resolution photography. It offers a minimum of 4GB memory at the area size of 165 mm2.

The three classes of miniSDHC and microSHDC cards (class 2, class 4 and class 6) can transfer data up to 2, 4 and 6 MB per second.


Unbuffered refers to a type of memory driven by its own memory controller module. Unlike registered memory, it does not make use of a store-and-forward system. Unbuffered memory can also be called unregistered memory. Unbuffered memory does not have control between the memory chips and the chipset. This means that data can be provided to the chips at any given time.

The use of unbuffered memory varies from one system to another. Most desktop and laptop computers support unbuffered modules. Certain systems require memory which is unbuffered, while other systems do not use the said type of memory. There are also systems that let the user choose between registered and unbuffered memory.

Gaming systems normally utilize unbuffered memory as it enables work stations to properly interact with one another. In addition, unbuffered memory is capable of supporting advanced and heavy graphical interfaces which are common in gaming systems. On the other hand, there are systems such as server class systems that normally prefer other memory types.

Unbuffered memory modules can be determined by examining the hardware. The user needs to look at the leads that are beside the first notch. The module is unbuffered if the leads have an uneven spacing between them. Also, a module that is unbuffered has a larger Printed Circuit Board (PCB) next to each lead.

An important thing to remember when using unbuffered memory is that it should never be interchanged with buffered or registered memory. Installing the wrong type of memory on the system will offset the memory module’s notch. This will make the module unusable.

How to Test your Computer Memory

When your computer starts to act differently, the first thing you should test is its memory. Problems in the computer’s memory, no matter how small, can cause erratic behavior in your computer that may lead to system crashes.

If the memory of your computer is corrupt, your computer may beep constantly or will not boot at all. You can also come across frequent random computer crashes exhibiting fatal exceptions, illegal operations, and general protection fault error messages.

You can test your computer memory by following the steps outlined below.

Steps on How to Test Computer Memory

  1. Visit official memory test websites.
  2. You can visit official memory test websites to download the user guide and memory test software. Normally it takes less than 30 minutes to finish the process. The result will indicate if you have a deteriorating memory component.

  3. Learn about memory test software programs.
  4. You need to learn about the different memory test software programs developed to test computer hardware and memory. Locate these programs using search engines such as Yahoo! or Google.

    The two most common memory test software used today are MS Memory Diagnostic and Memtest86.

  5. Test the memory stick.
  6. If the memory test software detects errors ran, you have to find out which memory stick has the problem.

    If you have only one RAM stick connected to the motherboard you can simply replace it. However, if you have two or more RAM sticks running, it is recommended that you pull out the sticks one by one and run the test on each memory stick to determine which one is defective. You do not have to replace all memory sticks when only one has a problem.

  7. Buy a commercial hardware computer memory tester.
  8. Commercial hardware computer memory testers are available in many stores. They are specifically developed to test computer memory. You can contact your local computer repair center to ask for information regarding the product and the pricing.

  9. Test the motherboard.
  10. You also have to test the motherboard. Sometimes you will have a perfectly good memory stick but a defective motherboard. However, you need to be aware that testing the motherboard is quite difficult, so you may need to hire an expert to do it.


Firmware is a type of computer program that is inherent in the hardware device. An example of which is the microcontroller. As the name implies, this program is neither a software nor hardware. However, it does function like software wherein it executes a computer program through a microcontroller or microprocessor. On the other hand, it is also tied into a hardware device that it cannot function when separated from the device.

Firmware was initially used for micro-programs but was later recognized for its functionality that could potentially replace hardware at a low cost. Firmware is a content of the hardware device that can be programmed. Hence, it may consist of a language for the microprocessor, or different configuration setting. Today, there are several devices whose firmware can be updated, which undergoes an electronic process for modern systems. Meanwhile, other processes of updating are also done by replacing the storage medium that contains firmware.

A firmware is capable of exposing an external interface. Although some modems do not have direct access to a firmware, there are also those that are combined with the hardware that enables to elicit response from the host system.

Most machines that are now attached to a modern system are also equipped with their own special software. Hence, the firmware is stored within the device’s ROM in itself. But it was recently discovered by most manufacturers that it is cheaper to load the firmware from the host system. Hence, most computers nowadays are unable to function unless it is connected with the requisite firmware. A device driver is needed to handle the firmware load.

The following products by Apple are capable receiving firmware updates:

  • AirPort
  • Bluetooth
  • PowerBook
  • Power Mac
  • iSight
  • iMac
  • iBook
  • video cards
  • optical drivers such as DVD-ROM or CD drives

Oftentimes, a new or modified version of firmware is produced by a third party to either create new features or unlock functionalities that are hidden. There are several examples of them on several devices while others are done through homebrew games for consoles. Once it is penetrated, it allows access into general computing functions which are previously limited.

These hacks are free and done through open source software. Since most firmwares today are equipped with an update facility, hackers take advantage of this in order to let devices run or install themselves.


Double Data Rate Synchronous Dynamic Random Access Memory, or DDR SDRAM, is a type of memory microcircuit commonly used in computer processors. It is the later improvement over regular Synchronous Dynamic RAM, also known as Single Data Rate SDRAM (SDR SDRAM).

Advantages of DDR SDRAM

The following are some of the advantages DDR SDRAM has:

  • DDR SDRAM can achieve two times as much the bandwidth (bit rate) compared to the SDR SDRAM through double pumping. This means moving data on both edges (rising and falling) of the clock signal without changing the frequency of the clock and implementing the burst-mode-data-transfer.
  • DDR-SDRAM consumes less power. That is why it is specially suited for notebook computers.
  • It has the capacity to transfer data 64 bits at a time at 100 MHz bus frequency. You can get the maximum transfer rate of DDR SDRAM by using the formula below:
  • Transfer rate = (memory bus clock rate) x 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte)

    Transfer rate = 100 MHz x 2 x 64 / 8
    = 1600 megabytes/second (maximum transfer rate)

Different Alternatives

  • DDR2 SDRAM outdated the DDR SDRAM. Though it works with the same principle as that of the DDR SDRAM, DDR2 SDRAM developed several modifications to facilitate higher clock frequency.

    The pre-fetch buffer width of DDR SDRAM is only 2 bits compared to the 4 bits deep of DDR2 SDRAM. Despite the successful clock speeds of DDR2, the general performance was no greater in the early implementations because of its high latencies. It gained public attention by the end of 2004 when lower latencies became available.

  • Rambus XDR DRAM, which is a competing product of DDR2 SDRAM, is another alternative to DDR SDRAM. However, DDR2 SDRAM has become the standard because XDR lacks hardware support.
  • DDR3 SDRAM superseded DDR2 SDRAM and became the new standard and an alternative for DDR SDRAM. It provides new features and even faster performance.
  • The Rambus Dynamic RAM can also be an alternative of DDR SDRAM. However, it is expensive compared to other memory chips and most producers dropped their support to their chipsets.


DDR2 SDRAM is short for Double Data Rate Two Synchronous Dynamic Random Access Memory. It is a RAM (Random Access Memory) technology commonly used in electronic engineering for high-speed storage of data in a personal computer or other digital devices.

It is part of the SDRAM (Synchronous Dynamic RAM) family known for storing memory in memory cells. It is the second generation of DDR SDRAM and one of the many DRAM (Dynamic RAM) implementations. DDR2 SDRAM is an evolutionary improvement over its predecessor.

Improvements in the DDR2 SDRAM

DDR2 SDRAM has the following features:

  • DDR2 SDRAM can run the external data bus at a rate that is two times as fast and efficient than the original DDR. It can transfer four bits of data per memory cell cycle. This innovation is possible because the original clock rate of the DDR is abandoned, operating half the clock rate (one quarter of the data transfer rate) of the memory cells.
  • There is an improvement in the prefetch buffer of DDR2 SDRAM. It is now four bits deep compared to DDR SDRAM’s two bits deep prefetch buffer width.
  • Prefetch buffers are memory cache placed on recent RAM modules that store data prior to its actual usage. The thickness of the prefetch buffer increases with every succeeding advancement in the modern DDR SDRAM modules. This helps in keeping up with the decrease in heat production and increase in bandwidth, CAS latency, and operation frequencies.

  • DDR2 SDRAM has read latencies between four and six cycles, twice higher compared to DDR SDRAM. This needs twice as much bus speed to achieve equal latency.
  • It operates on 1.8 V compared to DDR SDRAM’s 2.5 V.
  • In addition, due to its lower memory clock frequency, it facilitates power reduction in applications that do not require high-speed action.


EPROM stands for Erasable Programmable Memory. It is a type of chip that can hold data significantly longer than other types of ROM chips. EPROM can be programmed a number of times in contrast with PROM (Programmable Read Only Memory), which can be programmed only once.

The physical structure of an EPROM consists of several components. This chip is made up of rows and columns. Each intersection made by the rows and columns is called a cell. Every cell has its own control gate transistor and floating gate transistor. A layer of fine oxide separates the said types of transistors.

A grid row, also known as the wordline, is connected to the floating gate. The value of the cell is 1 if the connection of the floating gate to the wordline exists. On the other hand, the value of the cell is 0 if the connection between the floating gate transistor and wordline is removed.

EPROM uses a number of technologies for its features. It is configured and/or re-configured using a specific tool aptly known as an EPROM programmer. Configuring an EPROM involves changing the values of a number of cells from 1 to 0 through a process called tunneling. Tunneling is done by allowing electricity to pass through the control gate and floating gate to remove the link between the latter with the wordline.

To erase the EPROM programming, a device called an EPROM Eraser is used. The EPROM chip is placed under the EPROM Eraser which directs ultraviolet light to the EPROM chip. The energy of the ultraviolet light will unblock all the cells of the chip, subsequently changing all the values of the EPROM cells into 1.


DMA is an acronym for Direct Memory Access. This is a capability of computers that lets peripheral devices send data to the memory of the motherboard without any intervention from the CPU.

To carry out Direct Memory Access, the computer uses certain hardware known as DMA controllers. These controllers are built in to the chip of integrated processors. DMA controllers manage data transfer and regulate access to the system bus. Furthermore, these controllers can determine where to read and/or write data, monitor the amount of transferred bytes, and ensure proper CPU cycles.

DMA involves a set of processes. First, an event from the user, either a keystroke or a mouse click, would tell the DMA controller that data needs to be moved to the memory. The controller then sends a DMA request signal to the computer’s CPU. In this request, the DMA controller asks the CPU if the controller can use the system bus. The CPU then grants the request, gives a DMA acknowledge signal, and allows the DMA controller to use the system bus.

Afterwards, the DMA controller reads and writes data, as if it were the CPU. At this point, the CPU is in an idle state. Once the controller has finished the transfer, it will withdraw the request. The CPU will in turn remove the DMA acknowledge signal and reclaim its control of the system bus.

DMA helps computers perform faster. Since DMA does not need the CPU’s resources to read and write data in the peripherals as well as in the internal and external memory, the processor is then available for other tasks. This results to better multi-tasking and streamlined operations.


ROM, or Read-Only Memory, is an integrated-circuit (IC) memory chip. ROM contains configuration data which is required by computers to run and perform standard tasks. There is structured programming embedded in a ROM chip. It may therefore be considered as a combination of hardware and software.

ROM has permanent data which cannot be modified or deleted. This is because the data within a ROM chip is incorporated while it is being manufactured. As a result, ROM has fully-secured data. However, since ROM data is stored during the manufacturing process, an error in this stage will render the chip unusable. Developers of ROM address this issue by creating templates that simplify the process of making ROM and lessen the possibility of errors.

ROM is non-volatile. This means that the data within a ROM chip is retained even when power is lost or turned off. This further adds to the security and reliability of the data within ROM.

ROM is often associated with RAM, or Random Access Memory. This is because these two components provide the user with access to stored data. However, the data within RAM is lost when there is no power. Hence, RAM is appropriate for short-term memory. On the other hand, ROM provides long-term memory due to its non-volatile characteristic and because it has data that has been permanently etched into it.

The ROM chip consists of rows and columns. These rows and columns form a matrix of cells. Each cell has a value of either 0 or 1. The manufacturer of the ROM chip determines the value of each cell during the chip’s production. Finally, a diode is attached. This component manages the flow of electric current in each cell.


SODIMM is short for Small Outline Dual In-line Memory Module. It is a type of computer data storage manufactured using miniaturized electronic circuits called integrated circuits.

It is a smaller and thinner alternative of the Dual In-line Memory Module (DIMM), and approximately half the size of standard DIMMs.

SODIMM is frequently utilized in systems with space restrictions, such as high-end upgradable office printers, portable or notebook computers (laptops), networking hardware (like routers), and small footprint computers such as PCs with a Mini-ITX motherboard.

Types of SODIMM

There are four types of SODIMM. They are as follows:

1. The first type is the 72-pin SODIMM. It has a small cut out underneath the module next to the pins. This guarantees that the modules can only be inserted one way.

This type of SODIMM is frequently utilized in the Pentium 2 laptop computer system. Its memory capacity ranges from 8, 16, to 32 megabytes. In addition, this module comes in a 64-bit configuration.

2. The second type is the 100-pin SODIMM. This type of SODIMM has two notches that support a 32-bit data transfer.

3. The third type is 144-pin SODIMM. It has a cut out along the gold pins and a single notch near the center. Like the 72-pin SODIMM, this type of SODIMM can only be inserted one way.

It is usually utilized in computers compatible with PC100 and PC66 SDRAM. Its memory capacity ranges from 16 to 256 megabytes.

In addition, this module comes in both 72 bit and 64 bit Error Correcting Code (ECC) configuration.

4. The last type is the 200-pin SODIMM. It has a single notch closer to one side. Its memory capacity ranges from 64 to 512 megabytes.

Like the 144-pin SODIMM, this module comes in both 72 bit and 64 bit Error Correcting Code (ECC) configuration.

It has two distinctions for finding the notch almost indistinguishable to the naked eye.

If the notch is positioned further outboard, it signifies the DDR class of memory. When it is situated nearer to the center of the board, it indicates a DDR2 class of memory.

DDR and DDR2 classes of memory are not identical therefore the different notch locations prevent incorrect installation.

Installation Guide for SODIMM Memory Module

When installing SODIMM Memory Module, make certain that you are well grounded. You can wear a wrist strap or other type of static control device to avoid static electricity from storing onto your body. It should also be in conjunction with the model’s specific manual.

Here are the steps to install a SODIMM Memory Module:

1. Make sure the power cord is unplugged and the battery is removed before beginning the installation, especially if the SODIMM is being installed into a notebook computer with an installed battery.

2. Locate where to access the memory slot for installation. It is usually located under the keyboard. It can also be accessed through a door beneath the machine. You have to refer to your computer’s manual to carry out this step.

3. After ensuring that you’re well grounded, take the memory chip by its sides or top. Never touch the gold contacts because even a small amount of oil from your fingers can ultimately interfere with the connection.

4. Insert it at a 30 to 45 degree angle while pushing tightly but gently into the expansion slot. Continue pushing until the security has fastened firmly on the sockets and has locked into place on each side of the module.

5. In majority of installations, SODIMM modules can be inserted to any accessible expansion slot. However, others require the memory to be installed in a particular order based on the module’s capacity. You have to verify the correct installation sequence for your configuration by checking the manual.

6. Switch on the computer and follow the instructions from the computer’s manual on how to recognize newly installed memory. Most computers will automatically identify the added memory being installed.

For more information on SODIMM read:

  • DRAM

    DRAM is an acronym for Dynamic Random Access Memory, the most common form of Random Access Memory (RAM). It has the capacity to store every bit of data in a separate capacitor within a microcircuit.It is a highly volatile memory device because data can be lost when the power supply is removed.

    Difference Between DRAM and SRAM

    Dynamic RAM (DRAM) is composed of large arrays of very small capacitors. Every capacitor is slowly leaking energy; the information stored will ultimately fade except if the capacitor charge is refreshed from time to time.

    DRAMs with an asynchronous interface can react faster to changes in control inputs compared to those with synchronous interface that waits for a clock signal before reacting.

    Refreshing DRAM involves reading its contents and instantaneously writing them back. If one or more of the capacitors leaks enough energy and will not be corrected immediately, data corruption will eventually happen.

    Due to its refresh requirement, it is termed as a dynamic memory as opposed to Static RAM (SRAM) and other static memory. SRAM has faster capacity yet is much more expensive compared to DRAM. Both DRAM and SRAM, however, are highly volatile RAM so their contents will be lost if the power supply is turned off.

    Advantage of DRAM

    The main advantage of Dynamic RAM (DRAM) is its structural simplicity. It requires only a capacitor and one transistor per bit, as compared to six transistors used in SRAM (Static RAM). As a result, it can reach a very high density.

    Dynamic RAM Packaging

    For economic purposes, Dynamic RAMs are generally used on large main memories found in non-handheld game consoles such as Xbox and Playstation, workstations and personal computers.

    Other parts of the computer, such as data buffers and cache memories found in hard disks, generally use the Static RAM (SRAM).

    Variants of DRAM

    The following are some of the common variations of DRAM and their specific descriptions:

    1. Asynchronous Dynamic RAM – This variant of Dynamic RAM is the basic form from which all other variants were derived.

    An Asynchronous DRAM chip has several number of address inputs (usually 12). It has power connections and only a few number of bidirectional data lines (usually 1 or 4).

    2. Synchronous Dynamic RAM (SDRAM) – It is a type of computer memory in solid state, which means that it is based exclusively on the semiconductor, such as bubble memory, chips and transistors.

    There is no moving part or mechanical action needed, although a substantial quantity of electromagnetic action occurs within.

    3. Double Data Rate (DDR) SDRAM – It is a later improvement of Synchronous Dynamic RAM. It is the type of memory microcircuit commonly used in computers.

    It has the capacity to achieve twice the bandwidth (bit rate) compared to its predecessor (Single Data Rate SDRAM) through double pumping, the moving of data on the falling and rising edges of the clock signal without changing the frequency of the clock.

    4. Video DRAM (VRAM) – It is a double-ported variant of Dynamic RAM. It is usually utilized to store the frame-buffer in several graphics adapters.

    Since it is double-ported, it has two sets of data output pins that can be used simultaneously. The DRAM port, which is the first port, is accessed by the host computer in the same manner done in traditional DRAM. The Video port is the second port, which has the capacity to provide high-speed data channel for the graphics chipset.


    DDR3 SDRAM is short for Double Data Rate Three Synchronous Dynamic Random Access Memory. It is a RAM technology utilized for high speed data storage in a computer or in other digital electronic devices. It is part of the SDRAM (Synchronous Dynamic RAM) family of technologies, the third generation of DDR SDRAM and one of the many DRAM (Dynamic RAM) implementations.

    It is an evolutionary enhancement over its predecessor, the DDR2 SDRAM (Double Data Rate Two Synchronous Dynamic Random Access Memory).

    Improvements of DDR3 SDRAM

    Because of DDR3 SDRAM’s increased clock rate, its bit rate is higher. It also has reduced power utilization due to its 90mm fabrication technology.

    The words double data rate refer to the capacity of the computer bus to transfer data both in the falling and rising edges of the clock signal. This is the signal utilized in coordinating the actions of two or more circuits.

    The words synchronous dynamic RAM on the other hand, specify that this type of computer memory is in the solid state. This means that systems and devices are based entirely on a semiconductor.

    Benefits of DDR3 SDRAM

    Using a DDR3 SDRAM provides the following benefits:

    • It has the ability to transfer I/O data 8 times the speed of the memory cells it holds. As a result, it has a higher peak throughput and quicker bus speeds than past memory technologies.
    • The DDR3 standard works with microcircuits that have capacities ranging from 512 megabits to 8 gigabits, thus facilitating a maximum memory module size of up to 16 gigabytes.
    • DDR3 SDRAM has higher bandwidth (rate of data transfer or bit rate) performance, reaching up to approximately 1600 MHz.
    • There is an increase in performance even at low power.
    • DDR3 SDRAM has improved low power features and a much cooler thermal design.

    Disadvantages Of DDR3 SDRAM

    DDR3 SDRAM usually has higher CAS (Column Address Strobe) latency. However, it is compensated by a higher bandwidth, thus increasing overall performance under specific applications. Currently, it is also more expensive compared to its predecessor, the DDR2 memory.