Glossary of Acronyms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

EBIOS - Enhanced BIOS. A BIOS that makes it possible to use harddisks exceeding the infamous 504 (528 million bytes) barrier with DOS/Windows. The origin of this limit is the disk geometry (cylinders, heads, sectors) supported by the combination of an IDE drive and the BIOS software interface. Both IDE and the BIOS are capable of supporting huge disks, but their combined limitations conspire to restrict the useful capacity to 504MB. An enhanced BIOS circumvents this by using a different geometry when talking to the drive than when talking to the software. What happens in between is called translation. For example, if a drive has 1500 cylinders and 16 heads, a translating BIOS will make programs think that the drive has 750 cylinders and 32 heads.

ECC - Error Checking and Correction. The incorporation of extra parity bits in transmitted data in order to detect errors that can be corrected by the controller. Also, a function supplied the Intel Pentium processor which allows for the correction of single data errors and detection of 2 bit errors on data bus. This feature can substitute for RAM with parity.

ECC RAM - Error Checking and Correction Random Access Memory. An alternative to ordinary memory chip's use of parity to check their integrity during the power on self test phase of the initial bootup. The additional circuitry on ECC chips lets them test their integrity and correct memory errors on the fly.

ECD - Enhanced Compact Disks.

ECD - Extended Capabilities Port. A competing attempt with EPP (Enhanced Parallel Port) in an attempt to create a faster parallel port. Both are now a part of the IEEE 1284 parallel port specification, and many computer systems have parallel ports that can be configured for AT-style PS/2 style ECP or EPP modes. The choice can have an impact on system configuration and print performance.

In the old days, a parallel port dot matrix or daisywheel printer would print a page or two of text in a minute. The original PC used a 4 bit wide Centronics style parallel port, capable of about 100K/sec data transfers, which were more than sufficient to handle the load. Then laser printers upped the rate to about eight pages of text per minute. Windows came along and added proportional fonts and graphics, which added enormous amounts of data to the communications stream from computer to printer.

IBM provided help by introducing the 8 bit wide parallel port in the PS/2 line in 1987. These can be configured in two ways. One as Type 1 that does not require a DMA channel, or the other as a faster Type 3 that does use DMA. These were capable of 300K/sec.

To get full performance from printers, a marked improvement was required. Scanner and data storage manufacturers also wanted high speed bidirectional parallel ports. Two camps set about developing their own standards. Microsoft and Hewlett-Packard joined forces for the ECP design. It provides 8 bit bidirectional communication, has a provision for data compression, and uses a DMA channel to provide data transfer rates in excess of 2MB/sed. EPP, developed by Intel, Xircom, and Zenith Data Systems, also has 8 bit bidirectional communication, but does not provide compression or DMA channel support. Instead, it relies on software or IRQ channels for flow control. As a result, it is slightly slower, with a 2MB/sec maximum data transfer rate.

The advantage of ECP is that it is best suited for high speed transfers, particularly with printers, though it does tie up a DMA channel. EPP has control features that are more flexible, making it better suited for non-printing devices such as scanners and data storage. Both modes are supported by the IEEE 1284 specification.

IEEE 1284 also has one other important implication that should be kept in mind. Cables. Traditional parallel port connections have been made using a DB-25 25 pin connector at the PC end, and a 2 inch wide Centronics connector at the printer end. The new specification calls for a third type of connector. This is a miniature 26 pin Centronics style connector, referred to as a Type C connector. Traditional parallel cables typically have a length limit of 2 meters (about six feet), but if a Type C connector is used at both the computer and printer ends, and use a cable that meets IEEE 1284 specifications (including 18 pair foiled shielded, and braided shielded cable), lengths of up to 10 meters (33 feet) are supported. Specifications for IEEE 1284 cables are much more stringent than those for traditional parallel cables, which translates into higher costs. But using an IEEE 1284 cable with a newer printer is generally a good idea because you are assured of getting full speed data transfers between the computer and the printer.

ECP - Extended Capabilities Port

EDO RAM - Extended Data Out Random Access Memory. The most common and advanced type of RAM in use today which retains data for subsequent reads until the chip is reset. EDO RAM completes an I/O mode in one cycle as opposed to two cycles of the fast page mode RAM. EDO RAM 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. 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 motherboard is saved, which is good for notebooks. It also saves battery power. In short, EDO gives and increased bandwidth due to shortening of the page mode cycle, but it doesn't appear to be that much faster in practice.

EDPT - Enhanced Fixed Disk Parameter Table. An extension in standard BIOS of the ordinary FDPT (Fixed Disk Parameter Table) that makes use of undefined fields to provide information about the translation mode used for the harddisk. It uses a magic number (A0 in byte 3) and a checksum (in byte 15) to ensure that software cannot mistake random data for an EDPT. This practice is more or less standard across various flavors of translating BIOS's, with different magic numbers.

This table returns additional information for BIOS drive numbers 80H and 81H. The EDPT for BIOS drive 80H is pointed to by INT 41H, while drive 81H is pointed to by INT 46H. The EDPT is a fixed disk parameter table with an AxH signature byte. This table format returns two sets of CHS information. One set is the L-CHS and is probably the same returned by INT 13H=08H. The other set is the P=CHS used at the drive interface. This type of table allows drive >1024 cylinders or drives >528 MB to be supported. The translated CHS will have <=1024 cylinders and probably >16 heads. The CHS used at the drive interface will have <=1024 cylinders and <=16 heads. It is unclear how the IBM defined CE cylinder is accounted for in such a table. Compaq probably gets the credit for the original definition of this type of table.

EDRAM - Enhanced Dynamic Random Access Memory. EDRAM replaces standard DRAM and the SRAM in the level 2 cache on the motherboard, 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 level 2 cache is replaced with an SIC chip to sort out chip set 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.

EEPROM - Electrically Erasable Programmable Read-Only Memory. A type of non-volatile memory chip used to store semi-permanent information in a computer such as the BIOS. An EEPROM can be erased and reprogrammed directly in the host system without special equipment. Manufacturers can upgrade the ROM code in a system by supplying a special program that erases and reprograms the EEPROM chip with the new code. Also called a flash ROM. CMOS chip with Flash BIOS. Flash BIOS is upgradable.

EIA - Electronic Industries Association. Defines electronic standards in the United States.

EPP - Enhanced Parallel Port.  See ECP (Extended Capabilities Port).

EPROM - . Erasable Programmable Read Only Memory. An integrated circuit memory chip that can store programs and data in a non volatile state. These devices can be erased by ultraviolet light and reprogrammed with new data. CMOS chip with the software burned onto the chip. Not upgradable as a result.

EIDE - Enhanced Integrated Disk Electronics. Used widely in most computers since 1995. An EIDE interface chip can support four devices, but it has two interface cables each connecting two devices. The EIDE chip looks and acts like two IDE chips. EIDE supports a mixture of disks, tapes, and CD ROM Drives. EIDE allows disks up to 1 gigabit or larger. IDE and EIDE disks must be located in the computer and cannot be external. EIDE comes standard with any modern computer. Since the interface is built into the mainboard, it requires no slots. Also known as ATA-2. A specific Western Digital implementation of the ATA-2 specification.

EISA - Enhanced Industry Standard Architecture. A type of computer bus design or architecture specified by an industry consortium for x86-based computers. An EISA device uses cards that are upwardly compatible from ISA. EISA extends the 16 bit PCAT expansion bus to 32 bits and supports a 32 bit data interface while maintaining compatibility with existing 16 bit cards. EISA still runs at 8 MHz. The EISA expansion slots on a EISA bus are twice as deep as expansions slots found on an ISA system bus. An extension of the Industry Standard Architecture (ISA) bus developed by IBM for the AT. The EISA design was led by Compaq Corporation. Later, eight other manufacturers (AST, Epson, Hewlett-Packard, NEC, Olivetti, Tandy, Wyse, and Zenith) joined Compaq in a consortium founded September 13, 1988. This group became known as the "gang of nine." The EISA design was patterned largely after IBM's Micro Channel Architecture (MCA) in the PS/2 systems, but unlike MCA, EISA allows for backward compatibility with older plug-in adapters.

EMM - Expanded Memory Manager. A driver that provides a software interface to expanded memory. EMMs were originally created for expanded memory boards, but can also use the memory management capabilities of the 386 or higher processors to emulate an expanded memory board. EMM386.EXE is an example of an EMM that comes with DOS. A memory manager, such as HIMEM.SYS or EMM386.EXE, that is necessary in order to used Expanded Memory (special memory that lies outside of the CPU's normal address space). EMM divides expanded memory into 16 KB units called pages, plus 64KB of unused Upper Memory for EMS (Expanded Memory Specification) page frames.

EMS - Expanded Memory Specification. Sometimes also called the LIM spec because it was developed by Lotus, Intel, and Microsoft. Provides a way for microcomputers running under DOS to access additional memory. EMS memory management provides access to a maximum of 32M of expanded memory through a small (usually 64K) window in conventional memory. EMS is a cumbersome access scheme designed primarily for pre 286 systems that could not access extended memory. A specification for the use of Expanded Memory enabled by HIMEM.SYS and EMM386.EXE. Also referred to as the LIM (Lotus/Intel/Microsoft) Standard.

EPP - Enhance Parallel Port. EPP's advantage is that software is no longer required for data maintenance. It uses hardware shortcuts to reduce the large number of software commands previously required to transmit bytes and monitor transmissions. As a result, overall parallel port data transfer speeds have soared by as much as 15:1, to rates as high as 2 Megabytes per second, which is fast enough to drive multimedia CD ROMs and other high speed devices. When an I/o instruction is executed, EPP hardware synchronizes with an external peripheral. Since software isn't needed, transmissions take place in one I/O cycle. All handshaking is automatic.

ESCD - Extended System Configuration Data. A system which is part of PnP (actually a superset of EISA), that can store data on PnP or non-PnP EISA, ISA or PCI cards to perform the same function as the Windows '95 Registry above, that is, provide consistency between sessions. It occupies part of Upper Memory (E000-EDFF), which is not available to memory managers. The default length is 4K, and problems have been reported with EMS buffer addressing when this area has been used.

ESD - Electrostatic Discharge.

ESDI - Enhanced Small Device Interface. A hard disk drive interface developed by Maxtor in the early 1980's as an upgrade and improvement to the ST506 design. While the drive does not have an embeded controller, one of the most critical functions, encoding and decoding, is performed on the drive. This allows for faster communications and higher drive capacities. Uses the same cabling as ST506 interface, but carries different signals on each line.  A disk drive interface type which was briefly popular before IDE took over. An ESDI drive can transfer data between the drive and controller at 10, 15, or 20 megabits per second, which is faster than an MFM or RLL controller but slower than what is possible with an IDE or SCSI drive. See also IDE.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Compiled by Scott McArdle, MagnaCom Limited. I hope this list has helped you and if there is an item that should be on this list, please let me know. Thanks. PS, I've spent 100's of hours maintaining this list, please don't be a LAMER.