More about RAM:

Mostly when we talk about memory in a computer system, it is about RAM. It is the memory where a computer temporarily holds information that it is processing so the data can move quickly between the central processing unit or CPU, and the operating system. Essentially, RAM is where the CPU, the computer's main processing chip, does its "thinking".

The RAM is a read/write random access memory and the ROM is a read only random access memory. The term random access means that all storage locations in the memory are equally accessible and they do not require sequential access. Both RAM and ROM are random access devices.

The RAM is not a storage device like your hard disk where information is permanently held till you remove it. But when you open a file, it is loaded from storage (usually your hard drive or a diskette) into the memory (RAM). Hard disk or floppy disk is a magnetic storage device while RAM and ROM are semiconductor storage devices.

The RAM is the vital workspace of computing; the more RAM a system contains, the more information it can handle, and the more programs it can run at one time. It is the arrangement of information in RAM that determines how much data your PC can handle. The programs you use determine how much RAM you need. Graphical programs, for example, handle a lot of information and require more RAM than word processors or spreadsheets.

A RAM is a volatile memory or nonpermanent memory. Though RAM holds your information while you are working on it, but when the computer power is removed, RAM loses all of the information it contained. That means a blink in the power can erase hours of work if you have not been continually saving your work to permanent storage on a hard drive or diskette.

Many times when you have opened many programs and are doing jobs that require lot of memory, you are told that you are short on memory. And you get struck. Sometimes you can free up memory by shifting some files around. At times you need to physically add more RAM chips to meet your needs. Upgrading your RAM often is the cheapest way to speed up your computer.

More about ROM:

As already stated, the ROM is a read only memory. It is a type of memory that only can be read. There is no write operation. In a ROM data are permanently or semi-permanently stored. In a ROM in which data are permanently stored, the specified data are either manufactured into the device or programmed into the device by user and cannot be altered. In a ROM in which the data are semi-permanently stored, the data can be altered by special methods. A ROM is a nonvolatile memory. The stored data are retained even when power is removed.

ROM contains many of the basic instructions in BIOS (Basic Input/Output System, pronounced "BY-ose"). The CPU communicates with diskettes, hard drive, keyboard and other components through the BIOS contained in ROM chips. Without these the BIOS instructions, a computer will not even know how to read important files that are integral parts of starting up DOS. The BIOS must be set up and told exactly what kind and number of disks, ports, etc., exist in order to successfully intermediate between these parts and the CPU.

The BIOS is always stored in ROM. The ROM and BIOS are so interconnected that you will frequently hear the terms ROM BIOS and BIOS ROM.

BIOS is a layer between the hardware and the software. If the software wants to access the hard drive, it has to go through the BIOS to make sure that the hard drive is working. The BIOS translates between the two because hardware speaks a machine language and software speaks a programming language.

The BIOS is considered neither a hardware nor a software but a firmware. BIOS is like software because it contains instructions, but it is a hardware as it is an intricate part of the motherboard's circuitry.

The BIOS traditionally was built into the ROM chip during the manufacturing process. Later technology let ROM be programmed after the manufacturing process but only once. Now an increasing number of computers have ROM that can be erased and reprogrammed. Now a user can customize the BIOS instructions, to suit his needs.

Your computer's main ROM and BIOS are located on the motherboard. However, your computer may have other components with their own BIOS and ROM. For instance, a video card may have ROM programmed with video BIOS, which contains instructions that initialize the hardware on the video card. Video BIOs contains instructions different from main BIOS.

THE RAM family:

A RAM loses the information it contains once the computer loses electricity. Based on RAM's behaviour to lose information, there are two types of RAMs dynamic RAM and static RAM.

• Dynamic RAM:
  Dynamic RAM or DRAM (DRAM, pronounced "d-ram") is the most common type of RAM. In a dynamic RAM, the memory is stored on capacitors so it has such a poor retention that it has to remind itself every few milliseconds what it is supposed to remember. That is because the electric charges representing information only store data for a brief time. To compensate, the chips continuously read and rewrite the information in a process known as refreshing.

• Static RAM:
  Static RAM or SRAM (SRAM, pronounced "s-ram") chips consist of tiny transistors that are latches (on/off switches). These latches do not require refreshing, as long as the power is on. SRAMs are faster but more expensive and bulky than DRAMs, so your computer probably uses DRAM chips. SRAM is used only in special situations where speed is most critical.

As the CPUs are becoming more powerful, the DRAM technology is also going changes. So there are different types of DRAM, but essentially all of them are same. The Intel Pentium II processors use synchronous DRAM. The previous to this is extended data out (EDO) DRAM and still previous to this is fast-page mode (FPM) DRAM. Each one of these is incrementally a bit faster than the preceding architecture.

When it comes to types of RAM, your computer has what it has. You can not upgrade from, say, EDO RAM to synchronous DRAM, and the type of RAM is not a key consideration even when it comes to buying a computer. What is important is how much RAM you have.

Beware aware when installing additional RAM, especially accelerator cards, that you read the manual, as in most cases the manufacture will state what types of RAM are compatible with your device(s)

Separate from all of this is a type of RAM called video RAM (VRAM, pronounced "v-ram"), a special, more expensive type of RAM chip. VRAM chips can send information to the monitor at the same time they receive new information. This type of chip, which is frequently needed for graphics-intensive software such as three-dimensional games or graphics applications, often is placed on a video card to speed the creation of on-screen images.

The ROM Family:

In ROM data is permanently or semi-permanently stored. Based on this we have two types of ROMs the mask ROM and the PROM.

• Mask ROM:
  The mask ROM is referred to simply as a ROM. It is the type in which data are permanently stored in the memory during the manufacturing process.

• PROM:
  The PROM or the programmable ROM is the type in which data are electrically stored by the user with the aid of specialised equipment. Some PROM can be written to only one time.

  One of the most popular kinds of PROM is erasable PROM (EPROM, pronounced "e-prom"), which can be erased and reprogrammed when removed from the motherboard and exposed to ultraviolet light. EPROMs have a clear window covered with a label of some kind. Lifting the label exposes the semiconductor chip and lets it be reprogrammed. The correct dosage of ultraviolet light quickly erases the chips, and manufacturers change EPROMs with a special hardware device called a PROM blaster.

• Electrically erasable PROM [EEPROM, called "double-e-prom"]:
  Can be erased and reprogrammed with an electrical process in which a higher-than-normal voltage is applied to the chip. EEPROM is more expensive than EPROM, it is less popular and is rarely used on the motherboard of a computer.

New computers store BIOS on flash ROM, which like EEPROM, can be electrically rewritten. It is cheaper than EPROM and easier to reprogram. Once you find the correct installation diskette, updating the BIOS instructions in a flash ROM is a much easier than other type of PROMs.

What is SIMM?:

RAM are chips (integrated circuits) that reside on several small single in-line memory modules (or SIMMS). When we add more memory, we plug in additional SIMMs. SIMMs are small computer cards that are 4" long and about 1" wide. A side of the SIMM has a flat edge with a copper colour connector that you can slide into the port on a motherboard. The SIMM slides into the motherboard at approximately 45-degree angle, then clicks into a straight vertical position. Computers and devices have some chips soldered into the motherboard, with expansion slots for SIMM boards next to the permanent chips.

Generally SIMMs come in 30-pin and 72-pin formats. If your computer or device is set up to accept 30-pin SIMMs, you need to use adapters to fix 72-pin SIMMs.

• Additional Support
  • Amiga Realm: Technical Support > Hardware Technical Reference and Schematics
  • Amiga Realm: Knowledge Base Channel > Hardware Reference > Chipset Parts No.
  • Amiga Realm: Knowledge Base Channel > The Faqs > Memory [RAM] Management
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  • Big Book of Amiga Hardware