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See UPC.

Error Correction Code. A method used on hard disks to determine if an error has occurred in the data stored on the drive. A system of scrambling data and recording redundant data onto disc as it is pre-mastered. On playback, this redundant information helps to detect and correct errors that may arise during data transmission.

The ECC (Error Checking and Correcting), newest type of parity. ECC uses a whole series of bits to ensure the bytes are transmitted correctly. A true ECC module has each byte arranged like non-parity memory in 8-bit segments, the ECC bit are located at the end of the series of bytes in a four bit segment. You need a series of eight bits to perform ECC, which is why you need two ECC modules used together to perform the ECC function. ECC DRAM detects double-bit errors and corrects single-bit errors on the fly (Without needing to create an error message to the system.).

Error Detection Code. 32 bits in each sector which are used to detect errors in the sector data.

EDO is an advanced version of fast page mode (often called Hyper Page Mode), which  can be up to 30% better and only cost 5% more. EDO DRAM holds the memory data valid until the next CAS# falling edge, unlike standard fast page mode DRAM which Tri-States the memory. By using EDO DRAM, the CPU to memory bandwidth will increase from 100 MB to 200 MB per second.  Single-cycle EDO will carry out a complete memory transaction in 1 clock cycle; otherwise, each sequential RAM access inside the same page takes 2 clock cycles instead of 3, once the page has been selected. As it replaces level 2 cache and doesn't need a separate controller, space on the mainboard is saved, which is good for notebooks. It also saves battery power. In short, EDO gives an increased bandwidth due to shortening of the page mode cycle, but it doesn't appear to be that much faster in practice. It is mostly used as main memory on mainboards or video cards.

EDRAM (Enhanced DRAM)
Enhanced DRAM replaces standard DRAM and the SRAM in the L2 (level 2) cache on the mainboard, typically combining 256 bytes of 15ns SRAM inside 35ns DRAM.  Since the SRAM can take a whole 256 byte page of memory at once, it gives an effective 15ns access speed when you get a hit (35ns otherwise).  The L2 cache is replaced with an SIC chip to sort out chipset vs. memory requirements.  System performance is increased by around 40%. EDRAM has a separate write path that accepts and completes requests without the rest of the chip.

Electronically-Erasable Programmable Read Only Memory. A memory chip typically used to store configuration information. See NVRAM.

Enhanced Integrated Drive Electronics. The second generation of IDE technology that improves the data throughput of IDE hard disks and adds the capability of connecting CD-ROM drives to the same interface card as hard disks.

Extended Industry Standard Architecture. An extension of the 16-bit ISA bus standard introduced in 1988 that enhanced the capabilities and performance of the ISA bus standard. It allows devices to perform 32-bit data transfers.

Electronic mail. Messages sent by modem or other electronic means, which enables people to communicate over long distances in minutes as opposed to days.

A process by which a computer imitates the actions of another computer, so that the imitating system accepts the same data and executes the same computer programs as the imitated system.

Emulation Mode
A special mode in which a device such as a printer can emulate the actions of a different device. Communications programs commonly emulate terminals.

End User
You. A person who uses hardware and software.

Enhance IDE

Enhanced Small Disk Interface

Erasable Programmable Read-Only Memory. A computer chip which can be erased and written to but which will not lose its information when a computer is turned off.

Error checking
Any one of a number of methods used to verify that data sent from one place to another arrives at its destination without errors.

Extended System Configuration Data. In order to support the PnP devices, the BIOS requires a non-volatile storage (e.g., EPROM) to store the system resource information. The ESCD is a format for BIOS to store the resource information for PnP or non-PnP devices in a bit string format.

Enhanced Small Disk Interface. One type of hard drive specification for IBM PC and compatible computer. A high-speed hard disk bus interface used in the 1980s that has been superseded by SCSI due to ESDI's limitation of supporting only hard drives.

A popular networking technology featuring 10Mbps transmission speeds, running over thin coaxial (10Base-2), thick coaxial (10Base-5), or twisted pair (10Base-T) cables. Ethernet will support TCP/IP, AppleTalk (EtherTalk), Novell NetWare, and other communication protocols.

An implementation of the AppleTalk communications protocol that runs over Ethernet.

Even parity
See parity checking.

eXclusive OR (XOR)
A binary operation that compares two bits and yields a 1 only if the bits being compared are different, as shown in the table below.  See also OR.

1st Bit 2nd Bit Result
0 0 0
1 0 1
0 1 1
1 1 0

Expanded Memory (EMS)
Memory beyond the 640K limit of usable RAM in DOS which conforms to the Lotus-Intel-Microsoft (LIM) specifications for expanded memory. This memory is available only to DOS applications that can support it. It is an older standard which is being replaced by extended memory.

Extended Memory
In an IBM or compatible PC, the memory above the 1Mb address range. Uses XMS (eXtended Memory Specification).

Extended-memory Manager
On an IBM PC or compatible computer, a program that prevents different applications from using the same part of extended memory at the same time.

External SCSI Device
A SCSI device installed outside the computer cabinet. These devices are connected in a continuous chain using specific types of shielded cables.

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