Memory
*** also see Microsoft's I/O, Processor, and Memory Designs page (huge library of info)
As mentioned in the storage section - memory is not storage. Well, actually, it is, but the accepted practice is to refer to storage, as anything that is long-term. Memory is comprised of high-speed circuit chips, which temporarily store bits.
To repeat, memory is short-term integrated circuit chips. Temporarily, bits are held through the use of these chips, mounted on the motherboard. Memory is fast . . . bits are retrieved in the ns rage (ns is "nanoseconds", or 1/1 millionth of a second). Actually, most moderns memory chips are rated from 60-70 ns. Memory is expensive, and therefore usually holds small amounts of data. Today's PC's generally have just 64-128 MB (Mega-bytes, where 1 MB = 1024 k Bytes) of memory. Windows98 requires a minimum of 32 MB of memory - although Microsoft says 16 MB is OK - your PC will run like a dog that way.
The wizard
says - "this is a cute little
trick - the vendors lower the minimum requirements below what actually works
well. In this case, Microsoft realizes there are many people who's PC's have the bottom
requirements that they have listed, and those people will have horrible
performance - but it still "works". The companies simply do not
want to cut out that portion of business. So now we have millions of PC
owners with 16 MB of RAM, and horrible performance. But since they read
the box, and it says 16 MB is OK - they have no idea that by
spending an extra 80 bucks they could double their performance."
When most people say "Memory", they are talking about RAM. However, computers have three primary categories of memory. A couple of important notes about RAM :
How Much Memory is Enough?? - the age-old question. As a rule of thumb, if you are a typical user, who creates Microsoft Word and Excel files, and accesses the Internet for web browsing and email - then 32 MB is fine. If you play around with graphics applications such as Photoshop, and work with large files - then 64 MB would be appropriate. If you are a big gamer using 3D intensive graphically rich games such as Quake and Unreal, or if you are a heavy graphics specialist working with huge scans and/or video files . . . then 128 MB or even 256 MB would suit you best.
What about my Swap File ?? - the Windows swap file is a protected file that is used to simulate RAM, when your system requires more than what is available. Every system needs a swap file, even though you can run without one. You can designate your own swap file, but it is best (and I have played with this for years) to simply let Windows manage the swap file. You definitely want to use Norton Utility's "Speed Disk", because if will defragment your swap file (Microsoft's "defrag" utility will not) and it can also place the swap file at the fastest portion of the drive - the outer tracks (you need to run the Optimization utility to do this - Speed Disk does not do this).
NOTE: stay away from any and all "RAM Doubler" utilities - they have been proven not to work
ROM (read-only memory) -
Computers almost always contain a small amount of read-only memory that
holds instructions for starting up the computer. Unlike RAM, ROM cannot be written
to . . . well, at least not easily. Actually, all computers have a portion
of ROM called "Flash BIOS" (Basic Input/Output System), which can be
written to, or "flashed", by a special program on a diskette.
The reason for this, is because manufacturers find problems, bugs, and even just
improvements over time - and they issue upgrades to the BIOS on their websites -
which can be downloaded to a diskette, and then the BIOS is flashed to a new
revision. The type of ROM that allows this is called EEPROM (Electrically
Erasable Programmable ROM). You will probably never deal much with
ROM. It is the low-level memory in your PC, the foundation of the system,
used primarily during boot procedures. The data is held permanently, and
takes care of boot processes such as the POST (Power-On Self Test), which must
occur before anything else happens when a PC is tuned on. There is an
oasis of information - more than anyone could ever use, at Wim's
BIOS Page
NOTE: ROM is much slower than RAM - and often, the info most requiring speed in ROM, such as the BIOS, is copied into RAM upon boot up - this is known as "shadowing"
CMOS (Complimentary Metal Oxide Semiconductor) - this memory is sort of an overlay to the ROM of a computer - allows the user (you) to customize the BIOS. It holds the basic setup parameters of the PC hardware, and is configurable by the user. CMOS is comprised of very low-power transistors. A small, nickel-sized battery can hold the setup data within the CMOS for many years. You will notice that with most computers, as it begins to boot, you will see a quick message appear that says, "Hit Delete to enter setup". When you hit delete, you typically go into a blue DOS-like screen, with parameters, such as Hard Drive configurations, power consumption, security password, etc. - that you can adjust and save to the CMOS - typically by hitting the F10 key. An occasional problem is when someone sets a password in Setup (although few ever set this) and forgets it. The only way to reset the password at this point, is to remove the battery for a few minutes and reinstall - this clears out the CMOS settings. Just remember to leave it out for a few minutes, because there are capacitors that retain the charge for a short time.
RAM (Random-Access Memory)
- This is the same as main memory. When used by itself, the term RAM
refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This
is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it
requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data
was in RAM is lost.
72-Pin SIMMS
This picture show two RAM "SIMMS" (Single Inline Memory Modules). These are plugged into slots on the computer motherboard, and if with SIMM's, they must be added in identical pairs. Pentiums and Pentium II's used SIMM's, and Pentium II's and III's often use DIMM's - which do not require pairs. There are many other types of memory, including the new, extremely expensive, and despised "RDRAM" (Rambus DRAM).
RAM Speed
Memory is rated with a speed factor. For example, if a 72-pin, 128 MB SIMM is rated at 60 ns, then that is the amount of time it takes to deliver data. Older RAM was rated at 80, then 70, then 60 ns. Newer RAM is rated at 50 and 40 ns.
Memory makers can command a hefty premium for faster chips, so they'll test a batch of chips (at worst-case test settings, which means high temperatures since RAM is slower when hot) and then "bin them out" at different speeds. For example, they may make a run of RAM modules targeted for 60 ns. When completed, perhaps 90% test out at below 60 ns, and they are rated at 60 ns. If a module tests out at exactly 60 ns that is not considered good enough to rate it at 60 ns - it must be faster than it's rating !!! The other 10% are still worth $$$, so they take those that test out 60 to 69.999 ns and rate them at 70 ns. Anything that tests out at 70 ns or higher is trashed.
RAM Latency, or Delay
CAS Latency (Column Access Strobe Latency, or "CL") - CL2, CL2.5, CL4 etc.
These numbers indicate the CAS latency - the number of clock cycles that occur between the time the memory accesses the data it needs until the time that the data is fired through its interface pins. Lower CL numbers indicate faster (and more overclockable) memory.
CL2 modules wait two clock cycles before sending data. CL3 modules wait three clock cycles before sending data. CL2 modules are faster since they only wait two clock cycles and therefore are usually more expensive. Some systems may require either CL2 or CL3 memory.
The RAM has a CL rating - not your system !!
Why the overall difference between CL2 and CL3 memory is neglible - typically you will only see a 3-6% performance difference between CL2 and CL3, and this is only seen during only the most memory-intensive games & programs. It is true that CL3 delay is 50% longer than CL2, but the amount of time that memory is delivering data is very small when compared to the amount of time that the CPU is doing other tasks. The CPU may fetch data from RAM, and then spend the next 200 clock cycles doing arithmetic computations, sending data to the video card, running a virus scan, etc. In addition, most of the data that the CPU is using is already held in the L2 cache !!
Wait State
Any additional delay beyond the CAS Latency (CL) setting is called a wait state. The wait state is usually set by the system BIOS and can be customized on many computers is the bootup setup screen.
For example, if your PC uses CL2, and you set the Wait State to 1 in the BIOS, then each memory transfer from RAM to the bus will require 3 clock pulses (2 for the CAS and 1 for the wait state). Zero Wait State was a popular selling point that came out with the older Pentiums - which means the overall latency = the CAS rating (no additional delay, means the wait state = 0).
The RAM Modules
DIP (Dual Inline Package)
- ancient memory for the old, IBM 8088, 8-bit machines. The memory was soldered right onto the motherboard, using nine DIP chips per 8-bit memory line (the 9th was a parity bit). On the motherboard you would see a large matrix of DIP chips, Bank 1 would be a column of 9 chips, as would Bank 2,3, and 4. Each column handles 8 bits.
On the IBM 286 (80286) - which was used on AT and XT computers - the bus increased to 16 bits, so each bank consisted of 16 DIP chips (or 18 of parity was used - one parity chip per 8 bits).
SIMM - Single Inline Memory Modules
- when the IBM 386 (80386) PC's came out, it had a 32-bit bus, and they replaced each column of 8 DIP chips with a single, 30-pin SIMM. You must install 30-pin SIMMs in sets of 4 !!! A bank of SIMMS used 4 identical SIMMS to support the 32-but bus.
NOTE: 30 pins seems odd, but the number of pins does not always relate to the number of bits !!!
Each SIMM has either 8 chips (non-parity) or rarely, 9 chips (the ninth chip handles a 9th bit with each byte, called a "parity" bit - for error checking).
The IBM Pentium CPU's are 64 bit processors. SIMM's use 32 bits for every chunk of data - commonly called a 32-bit bus. Since the Pentium accesses data in 64-bit chunks, the SIMM's have to be installed in identical pairs. There are usually 4 slots on the motherboard, to accommodate two pairs of SIMM's. So, you could have, for example, a pair of 32 MB SIMM's, and a pair of 16 MB SIMM's. The pairs themselves do not have to be identical - so long as each pair is a matched set.
The memory technology SIMMS use is DRAM (Dynamic RAM). There are different flovors of DRAM, including standard DRAM, FPM (Fast Page Mode), EDO (Extended Data Out) and Burst EDO.
30-Pin SIMM - (DRAM)
72-Pin SIMM - (DRAM)DIMM - Dual Inline Memory Module
- expand on the storage power of SIMM's, by using a 64-bit bus. Pentium CPU's are 64 bit processors. Therefore, pairs of DIMM's are not required by Pentiums. Since DIMM's are newer than SIMM's, they typically are slimmer, yet have a higher capacity.
The memory technology 168-pin DIMMs use is SDRAM (Synchronous DRAM), where the speed is the memory is synchronized with the CPU clock. Common SDRAM DIMMs are PC100 (for the 100 MHz front side bus machines) and PC133 (133 MHz FSB).
168-Pin DIMM - (SDRAM)
Common types: PC100, PC133
NOTE: PC133 used to work in 100 MHz bus PC's but new PC133 does not !!
PC100 will work in both 100 and 133 MHz FSB machines but will slow down a 133 PCThe memory technology 184-pin DIMMs use is DDR RAM (Double Data Rate RAM). SDRAM only delivers data on the rising edge of the clock pulse, while DDR RAM delivers data on the rising and falling edges of the clock pulse, which double the data rate.
184-Pin DIMM - (DDR RAM)
Common Types: PC1600 (old), PC2100, PC2700, PC3200
240-pin DIMM - (DDR2 RAM)
Common Types: PC2-3200 (DDR2-400), PC2-4200 (DDR2-533), PC2-5300 (DDR2-667)
DDR RAM vs RDRAM (Rambus)
RDRAM (top) has 2 cutouts - DDR RAM (bottom) has one cutout
RIMM (Rambus Inline Memory Module) - (RDRAM - Rambus)
The RIMM was a revolutionary Intel brainchild, that quickly dissolved into disaster, and now is making a slow comeback with it's improved chips for the P4 systems.
C-RIMMs - if you use RIMMs, every memory slot must be filled !!! To save $$$ you can fill extra slots with a dummy RIMM, called C-RIMM (Continuity RIMM). The C-RIMM tricks the PC into thinking the slot has a valid RIMM module, although it has no real memory - just pins and some simply circuitry.
C-RIMM
16-bit RIMM (184 pins) vs 32-bit RIMM (232 pins)For pre-P4 systems - STAY AWAY FROM THIS !!! - This memory is so bad, that one of the biggest memory outlet in the world, Crucial.com - refuses to sell it !!! Bottom line, Intel made a vastly inferior product, which originally cost 5 times as much as the "good" RAM, and then they promoted it in a very insidious manner, and went ahead with it - instead of owning up to the fact that it was a failure and sicontinuing it. Many new PC's have RAMbus (RDRAM) - so be careful. Go for the 800 MHz machines that still use DRAM with DIMM's, of you can. In 1997, Intel announced that it would license the Rambus technology for use on its future motherboards, thus making it the likely de facto standard for memory architectures. However, a consortium of computer vendors is working on an alternative memory architecture called SyncLink DRAM (SLDRAM). RDRAM is already being used in place of VRAM in some graphics accelerator boards, but it is not expected to be used for the main memory of PCs until 1998 or 1999. Intel and Rambus are also working a new version of RDRAM, called nDRAM, that will support data transfer speeds at up to 1,600 MHz.
184-Pin RIMM - (RDRAM, or "RAMbus")
P4 Systems - a Rambus comeback !! Although most P4 systems use DDR Ram (due to the horrible reputation of RDRAM), the truth is, you can only get blazing speed on a P4 by using RDRAM !! Of course, you will need a P4 motherboard designed for RDRAM (see http://www.tomshardware.com/motherboard/20020624/index.html for details on six Intel 850E systems designed for Rambus). Intel is only able take the lead over its competitor, AMD Athlon XP, when used together with an RDRAM platform. Otherwise, if DDR RAM is used, Intel's lead over the Athlon XP is quite minimal.
Memory for the various CPU/Motherboards and Sockets/Slots
Older legacy systems were designed by IBM, and as time went on, Intel gradually took over. For the last 10 years the battel has been between two CPU architectures . . . Intel Pentium's and the lower-cost AMD (Advanced Micro Devices) K6, K7, and Athlon's.
First, a note on "Slocketts"
The slockett (see www.powerleap.com) takes a slow PII and turns it into a raging PIII.
The PII uses Slot 1, which is a long slot, that looks like a RAM slot, except it has black plastic guides on either end. PIII's use use Socket 7, which is a white plastic square mounted on the motherboard with hundreds of pins, that the flat, square CPU plugs into.
On the PII, the L2 cache was slow and ran at half the CPU speed. The slockett is an adapter that plugs into the Slot1 style CPU slot, and have a Socket 7 on their side - these are called "slocketts" (Slots-to-Sockets), and are extremely popular. They allow users with the slower Slot 1 L2 cache (1/2 the processor speed) - to upgrade to faster PIII Socket 7 processors with L2 cache's that run at the full processor speed. I have done this to my Dell 450 PII with L2 cache at 1/2 that at 225 MHz - upgraded it to a 1.4 GHz PIII with L2 at full CPU speed, which means my L2 cache went from 225 MHz to 1.4 GHz. What a difference that made !!!
Second, info on Pentiums
Third, the Memory with the various Systems
IBM AT, XT, and 286 - multiple banks (columns) of 8 or 9 (parity) 24-pin DIP chips
IBM/Intel 386 - 30-pin SIMMS
Intel 496 AMD K6 - 72-pin SIMMS (EDO, Fast-Page, or PC-66)
Pentium - 72-pin SIMM's - DRAM
CPU Tags MMX Instruction set extension for certain Pentium CPUs as well as the K6-2/III series which can be used for multimedia applications, but rarely applied. 3DNow! Instruction set extension for K6-2/III series which can be used for 3D applications, often applied. AFR 2.2V core voltage, max 70°C case temperature AFQ 2.2V core voltage, max 60°C case temperature AHX 2.4V core voltage, max 65°C case temperature AFX 2.2V core voltage, max 65°C case temperature AGR 2.3V core voltage, max 70°C case temperature Architecture/Cache onboard The L2 cache for Socket 7 CPUs is placed on the motherboard. It can vary between 512 and 2048KByte depending on the motherboard product itself. L3 The AMD K6-III has got 256KByte on-die (internal) L2 cache. The external cache on Socket 7 boards becomes then so-called L3 cache. Cache Motherboard cache (L2 or L3) runs in-sync with the system bus. Therefore it is not dependent on the CPU clock such as on the Pentium III or Athlon
The K6-III cache frequency of 100 MHz refers to the L3 cache. The L2 on a K6-III is on die and runs at full speed.
Pentium II - Pentium II systems use Slot 1 connectors, with a bus speed of 66 or 100 MHz. The L2 cache running at only 1/2 of the CPU speed. Systems with CPU speeds below 350 MHz had a 66 MHz FSB, and therefore used PC-66 SIMMs. Systems using a processor speed of 350MHz and higher use PC-100 or PC-133 SDRAM, of which we carry only PC-133. Most Pentium II systems support PC-133 memory, even if the system specifies PC-100 SDRAM. Check with your system or motherboard manufacturer. Your Pentium II system, if slower than 350MHz, probably uses PC-66 memory and bus.
Pentium III - Pentium II systems used Socket 370, and ranged from 300 MHz to 1 GHz. The PIII socket 370 architecture allowed the L2 cache to run at the same speed as the CPU - this was a major achievement and doubled the speed of the L2 cache !!
CPU Tags A Regarding Celeron 300A: Mendocino core instead of the older Convington core B Those Pentium-III processors operate at 133MHz Front Side Bus E Stands for 0.18 micron process and full speed cache PR Processor Rating used for Cyrix III. PR estimates the actual CPU speed in the field of 2D applications in comparison to typical 'MHz' CPUs. Note: The CPU clock is different from the P Rating! In 3D applications this rating is not valid anymore. Package CPGA Ceramic Pin Grid Array FC-PGA Flip Chip Pin Grid Array PPGA Plastic Pin Grid Array
Celeron 300A to 533 comes in PPGA, from Celeron 566 in FC-PGAConnectors Socket 370 (or PGA370) 370-pin socket mechanically suitable for Celeron, Pentium III and Cyrix III Note Older socket-370 motherboards have problems with Pentium IIIs and Celerons. They do not work if they don't support lower core voltages (1.65 instead of 2.0V). Furthermore, the new pin assignments have to be supported. Architecture/Cache Mendocino/Coppermine L2 cache is incorporated on die und runs at full speed. On all other Slot-1 CPUs the L2 cache runs at half speed.
Pentium IV (Pentium 4) - the P4 uses the same Bus speed as the fastest PIII computers - at 133 MHz. However, their top CPU speed goes way above that of the PIII. They use RAMBUS or DDR memory, depending on your motherboard. RAMBUS is available in a few different forms. Older PC-800 RAMBUS memory is universally compatible with systems that accept RAMBUS and use 400MHz FSB processors, and must be installed in pairs. PC-800 memory will not work with Pentium 4 processors that have a 533MHz or 800MHz FSB, and is no longer sold. For all new Pentium 4 processors, you will need either PC-1066 RAMBUS, or RIMM4200 memory. Both types run at the same speed, but use two difference interfaces. PC-1066 RAMBUS, like PC-800, must be installed in pairs (Need 512MB? Get two 256MB modules). RIMM4200 RAMBUS is a 32-bit technology, and can be installed one module at a time. Whether you'll use PC-1066 or RIMM4200 depends entirely on which type your motherboard supports. Please, check your manual before purchasing. No motherboard at this time supports both types simultaneously.
Chipset Intel 850E Intel 845G Intel 845E Introduction May 2002 May 2002 May 2002 Processor Plattform Socket 478 Socket 478 Socket 478 Supported CPU Intel Pentium 4 Intel Pentium 4 Intel Pentium 4 Chipset Northbridge Intel KC82850E Intel RG82845G Intel RG8245EES Chipset Southbridge Intel 82801 BA Intel 82801 DB Intel 82801 DB Front Side Bus Clock 100/133 MHz 100/133 MHz 100/133 MHz Memory Clock 400 MHz/533 MHz 100/133/166 MHz 100/133 MHz Asynchronous Memory Clock yes yes yes FSB-Overclocking up to 166 MHz up to 166 MHz up to 166 MHz max. # DIMM-Slots 4 3 3 max. Memory 2048 MB 3072 MB 3072 MB SDRAM Support no yes yes DDR SDRAM Support no yes yes VC SDRAM Support no no no RDRAM Support (Rambus) yes no no Dual RDRAM Support (Rambus) yes no no Ultra-DMA/33/66/100 yes/yes/yes yes/yes/yes yes/yes/yes Ultra-DMA/133 no no no Max. # USB 4 4 4 USB 2.0 no yes yes Max.# PCI Slots 6 6 6 Integrated Graphics no yes no AGP 1x / 2x / 4x yes / yes / yes yes / yes / yes yes / yes / yes AGP 8x no no no ACPI Features yes yes yes P4 Table
AMD K5, K6, and K7
CPU Tags MMX Instruction set extension for certain Pentium CPUs as well as the K6-2/III series which can be used for multimedia applications, but rarely applied. 3DNow! Instruction set extension for K6-2/III series which can be used for 3D applications, often applied. AFR 2.2V core voltage, max 70°C case temperature AFQ 2.2V core voltage, max 60°C case temperature AHX 2.4V core voltage, max 65°C case temperature AFX 2.2V core voltage, max 65°C case temperature AGR 2.3V core voltage, max 70°C case temperature Architecture/Cache onboard The L2 cache for Socket 7 CPUs is placed on the motherboard. It can vary between 512 and 2048KByte depending on the motherboard product itself. L3 The AMD K6-III has got 256KByte on-die (internal) L2 cache. The external cache on Socket 7 boards becomes then so-called L3 cache. Cache Motherboard cache (L2 or L3) runs in-sync with the system bus. Therefore it is not dependent on the CPU clock such as on the Pentium III or Athlon
The K6-III cache frequency of 100 MHz refers to the L3 cache. The L2 on a K6-III is on die and runs at full speed.
AMD Athlon and Duron - PC-133 SDRAM. Your system/motherboard manual contains this information, or you may call your system manufacturer to be sure. It should be noted that new Socket A motherboards use DDR memory and most accept Duron processors, however if you have a Duron processor in a motherboard that supports DDR, you should beat up the person who sold you that combo. DDR memory is useless overkill with a Duron processor. It is equivalent to equipping a Chevy Cavalier with Corvette wheels.
CPU Tags A stands for the new 0.18 micron manufacturing process on Athlon processors C stands for the new 0.25 micron manufacturing process on Athlon processors MMX Instruction set extension for Athlons which can be used for multimedia applications, but rarely applied. 3DNow! Instruction set extension for Athlons which can be used for 3D applications, often applied. Package CM Card Module, looks very similar to the Intel's SECC2 package Connectors Slot A (SC242) Connector for Athlon processors with 242 pins Note Slot A and Slot 1 (Intel) are mechanically identical (SC242). However, signals and protocols are different. Architecture/Cache Athlons 500 to 700MHz Cache runs at 1/2 CPU speed Athlons 750 to 850MHz Cache runs at 2/5 CPU speed Athlons 900 to 1000MHz (or 1.0GHz) Cache runs at 1/3 CPU speed
AMD Athlon XP - there are two types of Athlon XPs. Those that run at 266MHz FSB and those now running at 333MHz FSB. If your Athlon XP processor model is 2500+ or higher, it uses the 333MHz FSB. All other Athlon XP processors use the 266MHz FSB. When using a processor with 266MHz FSB, you may use any of the three types of DDR memory that your motherboard supports: The most universally compatible, and "slowest" of the three is PC-2100 DDR. This type of memory is accepted by virtually every DDR motherboard produced, and supports processors with 200MHz or 266MHz FSB. Up the ladder is DDR333 (PC-2700) memory, which is fast becoming the standard thanks to its faster speed and comparable pricing to PC-2100 DDR. This memory is supported by most new Socket A (Athlon XP) motherboards, and can handle Athlon XP CPUs with FSB speeds up to 333MHz. Finally, DDR400 (PC-3200) memory is the newest form of DDR RAM and exceeds the requirement for all Athlon XP FSB speeds. Because DDR400 theoretically is intended for CPUs with 400MHz FSB and because no Athlon XP CPUs now or in the immediate future will use a 400MHz FSB, DDR400 memory is mainly targeted towards the overclocker market for that processor.
Memory for Laptops
72 Pin SODIMM
72 Pin SODIMM's are typically found in Pentium II Laptop computer. They come in 64 bit configurations, with memory ranges of 8, 16 and 32 megabyte. These modules are designed around lower power consumption and only one voltage is offered, FPM and EDO at 3.3v. FPM and EDO are the standard DRAM types offered and the packaging is referred to as SOJ.
144 Pin SODIMM
144 Pin SODIMM's are typically used in PC 66 and PC 100 SDRAM Laptop compatible computers. It comes in both 64 bit and 72bit ECC versions and the memory ranges were 16 to 256 megabyte. The SDRAM chips used in 144 Pin SODIMM's are typically SDRAM in the form of TSOP packaging and available in 3.3v only.
