Cissp: Computer Architecture, Memory

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Synchronous DRAM (SDRAM)

Back 1

Synchronizes itself with the system’s CPU and synchronizes signal input and output on the RAM chip. It coordinates its activities with the CPU clock so the timing of the CPU and the timing of the memory activities are synchronized. This increases the speed of transmitting and executing data.

Front 2

Extended data out DRAM (EDO DRAM)

Back 2

This is faster than DRAM because DRAM can access only one block of data at a time, whereas this can capture the next block of data while the first block is being sent to the CPU for processing. It has a type of “look ahead” feature that speeds up memory access.

Front 3

Burst EDO DRAM (BEDO DRAM)

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Works like (and builds upon) EDO DRAM in that it can transmit data to the CPU as it carries out a read option, but it can send more data at once (burst). It reads and sends up to four memory addresses in a small number of clock cycles.

Front 4

Double data rate SDRAM (DDR SDRAM)

Back 4

Carries out read operations on the rising and falling cycles of a clock pulse. So instead of carrying out one operation per clock cycle, it carries out two and thus can deliver twice the throughput of SDRAM. Basically, it doubles the speed of memory activities, when compared
to SDRAM, with a smaller number of clock cycles.

Front 5

Process isolation

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Protection mechanism provided by operating systems that can be implemented as encapsulation, time multiplexing of shared resources, naming distinctions, and virtual memory mapping

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Dynamic link libraries (DLLs)

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A set of subroutines that are shared by different applications and operating system processes.

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Base registers

Back 7

Beginning of address space assigned to a process.
Used to ensure a process does not make a request outside its assigned memory boundaries.

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Limit registers

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Ending of address space assigned to a process. Used to
ensure a process does not make a request outside its assigned memory boundaries.

Front 9

RAM

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Memory sticks that are plugged into a computer’s motherboard and work as volatile memory space for an operating system.

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ROM

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Nonvolatile memory that is used on motherboards for BIOS functionality and various device controllers to allow for operating system-to-device communication. Sometimes used for off-loading graphic rendering or cryptographic functionality.

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Hardware segmentation

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Physically mapping software to individual memory segments.

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Cache memory

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Fast and expensive memory type that is used by a
CPU to increase read and write operations.

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Absolute addresses

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Hardware addresses used by the CPU.

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Logical addresses

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Indirect addressing used by processes within an
operating system.

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Stack

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Memory construct that is made up of individually addressable buffers. Process-to-process communication takes place through the use of these.

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buffer overflow

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Too much data is put into the buffers that make up a
stack. Common attack vector used by hackers to run malicious code on a target system

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Address space layout randomization (ASLR)

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Memory protection mechanism used by some operating systems. The addresses used by components of a process are randomized so that it is harder for an
attacker to exploit specific memory vulnerabilities.

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Data execution prevention (DEP)

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Memory protection mechanism used by some operating systems. Memory segments may be marked as nonexecutable so that they cannot be misused by malicious software

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Garbage collector

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Tool that marks unused memory segments as usable to ensure that an operating system does not run out of memory

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Virtual memory

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Combination of main memory (RAM) and secondary
memory within an operating system.

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Programmable read-only memory (PROM)

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form of ROM that can be modified after it has been manufactured. can be programmed only one time because the voltage that is used to write bits into the memory cells actually burns out the fuses that
connect the individual memory cells.

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Erasable programmable read-only memory (EPROM)

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can be erased, modified, and upgraded. holds data that can be electrically erased or written to. To erase the data on the memory chip, you need an ultraviolet (UV) light device

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electrically erasable programmable read-only memory (EEPROM)

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its data storage can be erased and modified electrically
by onboard programming circuitry and signals. This activity erases only one byte at a time, which is slow.

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Flash memory

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special type of memory that is used in digital cameras, BIOS chips, memory cards, and video game consoles. It is a solid-state technology, meaning it does not have moving parts and is used more as a type of hard drive than memory.

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relative addresses

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based on a known address with an offset value applied.