- How much must I have?

- Types of RAM

- SIMMs and DIMMs

- Other types of RAM

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What is... the memory RAM?


The principal memory or RAM (acronym of Random Access Memory, Random access memory) is where the computer keeps the information that it is using in the present moment; famous persons are them "gentle" in number of 32, 64 ˇ 128 that appear in the computers announcements.

Memory module in format DIMM

Physically, the memory chips are black rectangles that are usually welded in groups to a few plaquitas with "pines" or contacts, something like that:

The difference between the RAM and other types of memory of storage, like the diskettes or the hard disks, is that the RAM is very much (much more rapid, and that it resigns on having extinguished the computer, like these.


How much must I have?

Do not deceive itself: all that more, better. Clear it is that it costs money, so we will try to come to a satisfactory commitment, but never remaining short. First of all, do not complain: nowadays gentle of RAM it is at least of 300 pesetas, when for years it cost more than 5.000 pesetas (of then, not of now).

The quantity of necessary RAM is a function only of why you use his computer, what determines what operating system and programs it uses (although sometimes this logical order turns out to be tragically shaken). Synoptically, I recommend to him a minimal quantity of:


operating system only

less than 1 MB

Office computerization (processor of text, spreadsheet...)

2 to 4 MB

CAD (2D or 3D simple)

8 to 24 MB (according to version)

Graphs / Photo

8 to 32 MB (according to resolution and colors)

Games up to 386

2 to 4 MB

Modern games

8 to 16 MB

Windows 3.1x

only operating system (TWO included)

4 MB

Office computerization (processor of text, spreadsheet...)

6 to 10 MB

CAD (2D or 3D simple)

12 to 28 MB (according to version)

Graphs / Photo (average level)

10 to 32 MB (according to resolution and colors)

Windows 95

operating system only

12 to 16 MB

Office computerization (processor of text, spreadsheet...)

12 to 24 MB

CAD (2D or 3D simple)

20 to 48 MB (according to version)

Graphs / Photo (average level)

16 to 40 MB (according to resolution and colors)


16 to 48 MB

More information exists on the quantity of advisable memory in this article. How it sees, the same task under different operating systems and programs needs different RAM quantities, although the final score of the report, work of CAD or spreadsheet is the same. And the fact is that sometimes the computer science does not advance, except as business (not for you, skylight).

Like example, in 486 DX2-66 with 16 MB of RAM, the same 1 MB file in AutoCAD 12 for TWO flies, while in the same team with the version 13 for Windows 95 it crawls in a bad way, when it does not do that the team "is" "hung".

I dress this, if he is going to buy a new computer, to today I recommend to him 64 MB of RAM, and if possible enclosed 128. If I created that what he is interested in is to install more RAM, pulsate here to see how to do it; it is frankly simple.

Nevertheless, buy only the necessary one: a RAM increase will increase the yield only if there was scarcity. The empty RAM does not serve as anything, although as in everything, "better than on...".


Types of RAM

So many people since he wants: DRAM, Fast Page, EDO, SDRAM... and what is worse, several names for the same thing. We will treat these four, which are the principal ones, although in the paragraph it will find Other types of RAM practically all the rest (not few ones).

  • DRAM: Dinamic-RAM, or RAM to dry seasons, since it is "an original", and therefore the slowest (although he remembers: it is always better to have enough memory than to have the most rapid, but to walk scarce).
    Used up to the epoch of 386, his typical refreshment speed is 80 ˇ 70 (ns) nanoseconds, time this one that is late in emptying to be able to give entry to the following series of information. For it, that of 70 is more rapid ns that that of 80 ns.
    Physically, it appears in the shape of DIMMs or SIMMs, being the above mentioned of 30 contacts. One does not worry if so many xIMM him sounds to Chinese, it is told further down; but if he cannot wait any more, pulsate here.
  • Fast Page (FPM): sometimes called DRAM (or only "RAM"), since it evolves straight of her, and it is used for so much that seldom differentiates them. Slightly more rapid, so much for his structure (the way of Rapid Page) as for 60 is 70 ˇ ns.
    Used even with the first Pentium, physically it appears like SIMMs of 30 ˇ 72 contacts (those of 72 in the Pentium and some 486).
  • EDO: or EDO-RAM, Extend Byline Output-RAM. It evolves of Fast Page; it allows to begin introducing new information while the previous ones are going out (doing his Output), what makes her slightly more rapid (5 %, more or less).
    Very common in the Pentium MMX and AMD K6, with refreshments of 70, 60 ˇ 50 ns. He settles especially in SIMMs of 72 contacts, although it exists in the shape of DIMMs of 168.
  • SDRAM: Sincronic-RAM. It works of way synchronized with the speed of the badge (from 50 to 66 MHz), for what it must be the most rapid, from approximately 25 to 10 ns. Only it appears in the shape of DIMMs of 168 contacts; it is used in Pentium II of less than 350 MHz and in Celeron.
  • PC100: or 100 MHz SDRAM. Memory SDRAM capable of working to these 100 MHz, which the AMD K6-2, Pentium II use to 350 MHz and more modern mikes; theoretically it is a question of a few minimal specifications that must be fulfilled to work correctly at the above mentioned speed, although not all the sold memoirs as "of 100 MHz" they fulfill them...
  • PC133: or 133 MHz SDRAM. The most modern (and advisable).

To know how to identify "roughly discovered" the speed of refreshment (the ns) of a chip of memory, pulsate on this hypertie. Also there exists more information about the memory SDRAM and the PC100 between the Topics Related in the margin.



It is a question of the form in which there join the chips of memory, of the type that are, to get connected to the motherboard of the computer. There are a few plaquitas lengthened with connectors in an end; there is called he to the set a module.

The number of connectors depends on the bus of information of the microprocessor, which more than a bus is the highway for which the information goes; the number of rails of the above mentioned highway would represent the number of bits of information that he can handle every time.

  • SIMMs: Single In-line Memory Module, with 30 ˇ 72 contacts. 8 bits can handle those of 30 contacts every time, therefore in 386 ˇ 486, which has a bus of information of 32 bits, them needs to be used by us of 4 in 4 equal modules. They measure approximately 8,5 cm (30 c). ˇ 10,5 cm (72 c). and his sockets are usually of white color.
    The SIMMs of 72 contacts, more modern, handle 32 bits, by what they are used of 1 in 1 in the 486; in the Pentium it would be done of 2 in 2 (equal) modules, because the bus of information of the Pentium is the double of big (64 bits).
  • DIMMs: more elongated (approximately 13 cm), with 168 contacts and in generally black sockets; they take two notches to facilitate his correct laying. They can handle 64 bits at once, by what they can be used of 1 in 1 in the Pentium, K6 and Superiors. They exist for standard voltage (5 volts) or reduced (3.3 V).

And we might add the modules SIP, which were similar to the SIMM but with fragile welded legs and which are not used for enough years, or when quite or part of the memory is welded in the badge (case of some computers of mark).


Other types of RAM

  • BEDO (Burst-EDO): an evolution of the EDO, which sends certain information in "blasts". Slightly widespread, he competes in services with the SDRAM.
  • Memoirs with parity: they consist of adding to any of the previous types a chip that realizes an operation with the information when they enter the chip and other one when they go out. If the result has changed, an error has taken place and the information is already not trustworthy.
    Saying like that, it looks like an advantage; nevertheless, the computer only warns that the error has taken place, does not correct it. Moreover, these errors are so improbable that most of the chips never suffers them although they are working for years; for it, it has been years since all the memoirs are made without parity.
  • ECC: memory with errors correction. It can be of any type, although especially EDO-ECC or SDRAM-ECC. It detects information errors and corrects them; for really critical applications. Used in servants and mainframes.
  • Memoirs of Video: for graphic cards. Of minor to major yield, they can be: DRAM-> FPM-> EDO-> VRAM-> WRAM-> SDRAM-> SGRAM
    For more information on them, pulsate here to go to the corresponding paragraph of graphic cards.


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