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Ram & rom memories

This document provides information on different types of computer memory, including ROM and RAM. It discusses the main characteristics and uses of ROM types like PROM, EPROM, and EEPROM (including EAROM and flash memory). It also covers the basics of RAM like SDRAM, and specific types like SDR-SDRAM, DDR-SDRAM, and RDRAM. The document is intended to explain the differences between read-only and random access memory.

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RAM AND ROM MEMORIES BY: LUCÍA SACRISTÁN 4ºC ÁNGELA APARICIO 4ºA
Home Next INDEX •WHAT IS ROM? •CHARACTERISTICS •TYPES : • PROM • EPROM • EEPROM : -EAROM -FASH MEMORY •WHAT IS RAM? •TYPES • SDRAM : • SDR-SDRAM • DDR-SDRAM • RDRAM: • RIMM-RDRAM
Home WHAT IS “ROM”? Next WHAT TYPES CAN WE FIND? • It works as a storage medium, • used in computers and other electronic devices. • Data stored in this memory cannot be modified. so it is mainly used to distribute software that is very closely tied to specific hardware, and unlikely to need frequent updates. • It usually refers only to mask ROM (oldest type of ROM), which is fabricated with the desired data permanently stored in it, and can never be modified. According to Wikipedia; “Classic ROM chips are integrated circuits that store data physically, so that it is impossible to change their contents after fabrication. Other types of non-volatile memory allow some degree of modification.”
Home Next USES AND CHARACTERISITCS OF ROM • ROM usually stores the startup instructions for the computer, and it also helps to load the operating system. • Now, regarding reading and writing speeds; For those types of ROM that can be electrically modified, writing speed is always much slower than reading speed, and it may need unusually high voltage. Modern Flash devices achieve the highest write speeds of any rewritable ROM technology, with speeds as high as 15 MB/s(or 70 ns/bit), by allowing large blocks of memory cells to be written simultaneously.
Home • PROM Next Programmable read-only memory (PROM), or one-time programmable ROM (OTP), can be written to or programmed. Typically, this device uses high voltages to permanently destroy or create internal links within the chip. Consequently, a PROM can only be programmed once.
Home EPROM • Erasable programmable read-only memory (EPROM) can be erased by exposure to strong ultraviolet light (typically for 10 minutes or longer), then rewritten with a process that again needs higher than usual voltage applied. Repeated exposure to UV light will eventually wear out an EPROM, but the endurance of most EPROM chips exceeds 1000 cycles of erasing and reprogramming. Next •EPROM chip packages can often be identified by the prominent quartz "window" which allows UV light to enter. After programming, the window is typically covered with a label to prevent accidental erasure. Some EPROM chips are factory-erased before they are packaged, and include no window.
Home Next EEPROM • Electrically erasable programmable read-only memory (EEPROM) is based on a similar semiconductor structure to EPROM, but allows its entire contents to be electrically erased or rewritten, so that they don’t need to be removed from the computer or device. Writing or flashing an EEPROM is much slower than reading from a ROM or writing to a RAM. EAROM FLASH
Home EEPROM Next (EAROM & FLASH MEMORY) • Writing is a very slow process • It’s a modern type of EEPROM invented in 1984. Flash memory and needs higher voltage than can be erased and rewritten faster the one used when accessing than ordinary EEPROM, and newer data. EAROMs are intended designs feature very high endurance. for applications that require only partial rewriting. It may be • Modern flashes are fabricated now with a capacity as high as 32 GB as used as non-volatile storage, of 2007; this feature, along with its although it has already been endurance and physical durability, supplanted by another memory has allowed the newest flashes to replace magnetic in some which is supplied by mains applications (such as USB flash power and backed-up with a drives). lithium battery. • Flash memory is sometimes called flash ROM or flash EEPROM when used as a replacement for older ROM types.
Home WHAT IS “RAM”? Next • RAM (Random Access Memory) is a type of memory that computers use to store data and softwares to which it needs to access quickly. • It is a volatile memory, that is, the information stored inside vanishes when the computer is turned off; although there are also RAM memories that do retain the information, for example, flash memories. • The stored data does not only vanish when the computer is turned off, but that is also must be eliminated when the file containing data is not being modified anymore. • The computer will work faster depending on the quantity of gigabytes (or megabytes) of RAM memory it has installed in it.
Home TYPES OF RAM • SDRAM: SDR-SDRAM and DDR-DRAM • RDRAM: RIMM-RDRAM Next
Home SDRAM Next • SDRAM (Synchronous Dynamic Random Access Memory) refers to a family of dynamic memories of random access (DRAM) that have a synchronous face. They have been used from the early 1970s. SDR-SDRAM DDR-SDRAM
Home SDR-SDRAM Next • SDRSDRAM (Single Data Rate Synchronous Dynamic RandomAccess Memory) is a type of RAM memory, subtype of SDRAM. It has been used ever since the beginning of the 1970s. • SDR-SDRAM are synchronized memories, with access speeds between 25 and 19 nanoseconds that are introduced in DIMM modules of 168 contacts. • Most people think that the SDR-SDRAM are only called SDRAM, but it is not true because it is also possible to find other types of SDRAM, as DDR-SDRAM.
Home DDR-SDRAM Next • DDR SDRAM (Double Data Rate Synchronous Dynamic Random Access Memory) is a type of RAM memory, subtype of SDRAM, that has been used since the 1970s. • DDR allows certain modules of RAM memory – composed by synchronous memories SDRAM –, available as DIMM, to have the ability to transfer data simultaneously on the two different channels in a same clock cycle. DDR modules support a maximum capacity of 1 GB.
RIMM-RDRAM • RIMM (Rambo Itachi Machop Module) designs RAM memory modules that use a technology named RDRAM, developed by Rambus Inc. in the mid 1990s with an objective to introduce a memory module with higher working levels than SDRAM memory modules of 100 MHz and 133 Mhz, which were the only ones existent in those times.