- MOTHERBOARDS -
RAM (Random Access Memory) is your computers "thinking space" and only functions while your PC is turned on. Contemplate yourself in the morning when you wake up and start loading programs you have developed over the years (like "get out of bed", "walk to the shower", "take shower", etc. etc.) from your own 'hard drive' to your own `RAM' and you will understand how your PC works. The part of your brain that, in PC vernacular, is `RAM', clears all information stored in it as you fall asleep and (unless you are prone to personal dreaming) does not `come alive' until you wake up the next morning.
RAM (also called "Real Memory") performs the critical function in your PC of absorbing data and interacting with your processor on all programs (operating system and applications) while your PC is turned on doing it's thing (or your thing). While you are creating a document (making `inputs’ from your keyboard and mouse), it is temporarily stored in real memory and exists only in RAM until you save it to your secondary memory device (hard drive). Simply, Primary Memory assembles data from secondary memory and user inputs, provides the data input `to' and receives data output `from' your Central Processing Unit, and temporarily stores your work. If you lose power before you have `saved' your work, it's history!!
High Memory Allocations
Shown above are visual layouts of what your real memory looks like. Your conventional memory of 640K was a very critical area back in the DOS era, but now it is simply used in the boot-up process. High memory, as you can see, is primarily used for your video display while you are in the DOS mode, and for your system BIOS. After your system has passed it's initial checks (BIOS scan), the Windows extended memory manager (EMM386.EXE) takes over and gives you access to the 128MB (or whatever you have installed) extended memory board(s).
Remember, this is where all of the things happening in your PC are really happening - and when your computer is turned off, they are really gone unless you have saved them!
The `standard' SDRAM board between 1995 and 2000
A 168 pin SDRAM board
The standard board between 2000 and 2006
A 184 pin DDR SDRAM board
Arriving on the scene in about 2006
A 240 pin DDR2 SDRAM board
RAM HARDWARE BASICS:
There are two basic types of RAM: DRAM (Dynamic RAM) and SRAM (Static RAM). DRAM is the most common and least expensive computer memory. For you technical geeks, SRAM works on the principle of a switch that is turned on or off and requires 2 to 4 transistors for each bit (a bit has two states; on or off and is the smallest unit of memory storage and is made of one memory cell). DRAM, on the other hand, is based on a capacitor's ability to hold a charge and requires only one transistor per bit. Because DRAM cells are smaller than SRAM, manufactures can put more memory into the same size thus reducing the cost per bit. Did you understand all of that??
A few years ago real memory (Random Access Memory) boards were named SIMMs (for `single' inline memory modules) and were manufactured in 256KB, 1 MB, 4MB and 8MB sizes (I can remember when 1MB SIMMs cost $65 each) and had 30 `pin' connectors which interfaced with the motherboard. These boards are installed in "banks" on a motherboard, and a bank must have all slots filled to function. Based on the design of the motherboard, it took either 2 or 4 of these boards to fill a bank and make your computer work.
Next came the DIMMs (`dual' inline memory modules) which had 72 pins, came in 4MB, 8MB, 16MB and 32MB sizes, and fit into `one' or `two' slot banks. The price of a 4MB DIMM started at about $150 each and went up.
Until recently, the 168 pin SD (Synchronous Dynamic - long story) RAM board was the standard `real memory' on Pentium-grade motherboards and all work in a single slot `bank'. These boards are much faster than earlier vintage RAM and are available in 16MB, 32MB, 64MB, 128MB, 256MB & 512MB sizes. Also, they have been upgraded in speed with increases in technology from 66MHz to 100MHz to 133MHz to 150MHz and are marked as PC66, PC100, PC133, and PC150 SDRAM boards. Amazing as it seems, you can now buy a 256MB SDRAM board for around $30 - and I attribute the major drop in PC system prices to the drop in the price of RAM!!
To make things more complicated, if you were building an Intel P-IV system, you needed "RAMBUS" RAM for the thing to work. Rambus modules rated for 300-MHz operation are termed PC600 RIMMs (the 300-MHz clock x 2). By 1998, Rambus had advanced to dual 400-MHz channels, so the effective clock rate became 800 MHz (400 MHz x 2) with a 16-bit data bus, yielding a peak bandwidth of 1.6 GBps. This doubles to 3.2 GBps when you add a second channel. 184-pin Rambus modules rated for 800-MHz operation are called PC800 RIMMs. Today, Rambus is advancing to 1,066 MHz (PC1066) and 1,200 MHz (PC1200) for even higher performance. All of this technical double-talk aside, based on a recent Intel decision to be more flexible (due to competition), you now have the option of DDR RAM (below) or RAMBUS on Intel P-IV motherboards. Further, I have read that Intel is seriously considering totally switching to DDR technology vs. their original RAMBUS choice for the P-IV.
Around the year 2000, 184 pin DDR (double data rate) RAM became the hot item. Reviews said it increases your system performance by 10% to 20% (whatever that means). To compete more closely with RDRAM, SDRAM creators developed memory that would perform two operations per clock cycle. This is why this memory is called double data rate or DDR SDRAM. For a 100-MHz FSB, DDR SDRAM provides twice the bandwidth (8 bytes x 100 MHz x 2) or 1.6 GBps. For a 133-MHz FSB, DDR SDRAM can reach a peak bandwidth of 2.1 GBps (8 bytes x 133 MHz x 2). With a 166-MHz FSB, DDR SDRAM can offer a peak bandwidth of 2.7 GBps (8 bytes x 166 MHz x 2). These are called DDR200, DDR266, and DDR333 for 100-MHz, 133-MHz, and 166-MHz speeds, respectively. But memory makers often name the modules based on their bandwidth, such as PC1600 (1.6 GBps), PC2100 (2.1 GBps), and PC2700 (2.7 GBps). A DDR SDRAM module uses 184 pins (like a RIMM). Since DDR SDRAM builds on well-established SDRAM technology, it was cheaper than Direct Rambus modules.
DDR technology has grown in leaps and bounds - and the board nomenclature is, at best, confusing. Here is a table that I hope will make it a little simpler:
DDR-I
PC1600 = DDR 200MHz Data-rate (100 Clk x 2) 1.6Gb/Sec
PC2100 = DDR 266MHz Data-rate (133 Clk x 2) 2.1Gb/Sec
PC2400 = DDR 300MHz Date-rate (150 Clk x 2) 2.4Gb/Sec
PC2700 = DDR 333MHz Data-rate (166 Clk x 2) 2.7Gb/Sec
PC3000 = DDR 366MHz Data-rate (183 Clk x 2) 3.0Gb/Sec
PC3200 = DDR 400MHz Data-rate (200 Clk x 2) 3.2Gb/Sec
DDR-II
DDR2-400 = 400 MHz = PC2-3200 = 3.2 GB/s
DDR2-533 = 533 MHz = PC2-4200 = 4.2 GB/s
DDR2-667 = 667 MHz = PC2-5300 = 5.3 GB/s
DDR2-800 = 800 MHz = PC2-6400 = 6.4 GB/s
DDR-III RAM
DDR3 RAM is the next step in the DDR memory technology. It again increases performance and efficiency over its predecessor. The DDR3 memory specification begins at DDR3-800 or PC3-6400.
I have had questions on mixing different speed DDR `sticks' on the same motherboard. Only answer I can get from other experts is that it all depends on the motherboard. Try it and see if it works (can't hurt anything). If it does work, both boards will default to the speed of the slowest board.
RAM and SYSTEM RESOURCES:
I have had a couple of questions on my www.allexperts.com volunteer job about how RAM affects system resources. Well, I do not really understand myself what I have learned so far about the relationship between available RAM and system resources. I have played with adding and subtracting RAM and watching for changes in resources, saw significant improvements in resources with increases in RAM up 128MB, but beyond that, saw little change at all. My resources are the lowest when I'm on-line (around 50%) and I'm running 256MB. I have read that you shouldn't worry about system resources until they get down to around 20% - but that is just an opinion. I do know that lots of RAM really helps when you are running a DVD player or working with heavy duty graphics in PowerPoint or something - but typically any RAM over 256MB in a Win 98 environment is an overkill. To hear what I have to say about optimizing system resources, go to Tips & Tricks.
UPGRADING YOUR RAM:
At today's prices of RAM everyone seems to be upgrading - and it is the most cost effective and simplest performance improvement you can make. If you are still running 128 or 256 MB of RAM in your PC go out and buy some more!
WHAT TO BUY: A lot of confusion exists about matching the speed of your motherboard (66MHz, 100MHz, 133MHz, etc.) to the speed of your RAM. According to all the information I have been able to dig up, everything up to an including PC150 RAM will work on any ATX (Pentium II or faster) motherboard with a clock of 66MHz or better. The limitation you run into is that the RAM speed defaults to (will not be any faster than) the speed of your motherboard - so you do not get full benefit of the faster RAM. There are a few `smart' motherboards that will let you set your RAM speed higher than your motherboard clock, but these are very rare (and expensive). An important thing thing that I have experienced personally is that you should not try to `mix' RAM boards of different speeds on the same motherboard! Either your PC won't boot up at all or performance will be very erratic.
INSTALLATION: Installing new RAM is the simple process of taking the cover off your PC, looking for a board (like one of the ones above) plugged vertically into a `bank' (which is one of 2 to 6 parallel slots on your motherboard), and plugging the new board into an empty slot (straight down after matching the `key' notches on the RAM board with the plastic `guides' in the slot). If your new RAM is a different speed than your existing RAM, remove the old RAM by pressing down the white tabs at each end of the slot, and install the new board in its place (press down firmly at each end until the tabs lock back into place). Put the cover back on and that's it!!
