What Is RAM? RAM Details – How much ram do i need?
RAM stands for Random Access Memory. Our system uses RAM to store working parts of the operating system temporarily, and the data your applications are using actively. RAM is not a permanent storage, It’s the short term memory of the computer.
Think the RAM is like an entire office workstation, while the CPU cache is like the actual working area where you actively work on a document. The more RAM means having a bigger desk that can hold more bits of paper on it without becoming messy.
Unike an office desk, RAM cannot act as permanent storage. RAM has volatile memory The contents of your system RAM are lost as soon as you turn the power off.
Shopping for RAM can be confusing.
- What’s the difference between DDR3 and DDR4?
- What’s the difference between DIMM and SO-DIMM?
- Is there a difference between DRR3-1600 and PC3-12800?
- Is RAM latency and timing important?
RAM Usually Means SDRAM
Do not confuse SD-RAM with SRAM, in which SRAM stands for Static RAM. Static RAM is used mostly in CPU cache memory & it is much faster but, limited by its capacity. Static RAM can be found in compact devices like tablet, mobile phones. It the onboard soldered RAM. As the SRAM works same as SDRAM, but in SRAM we lost the future upgradation option & also if RAM fails we even can’t change it manually. Either we need to purchase other device or need to paid higher for getting it to be repaired.
Form Factors Of RAM
For the most part, RAM comes in two sizes:
- DIMM (Dual In-Line Memory Module), which is found in desktops and servers, and
- SO-DIMM (Small Outline DIMM), which is found in laptops and other small form factor computers
Though the two RAM form factors use the same technology and functionally work in exactly the same way, you cannot mix them. You can not plug a DIMM stick into a SO-DIMM slot, and vice versa because the pins and slots doesn’t match.
SDRAM Vs SRAM
Do not confuse SD-RAM with SRAM, which stands for Static RAM. Static RAM is mostly used in CPU cache memory & It is much faster, but limited by its capacity. Static RAM can be found in compact devices like tablet, mobile phones. As the SRAM works same as SDRAM, but in SRAM we lost the future upgradability option & also if RAM fails we even can’t change it manually. Either we need to purchase other device or need to paid higher for getting it to be repaired.
To understand the various advertised specifications & details for RAM, we’ll discuss the CORSAIR Vengeance LPX as a example.
There are 4 main data points worth mentioning.
- Capacity (8GB)
- Stick Type (DDR4)
- Cell Type (DRAM)
- Clock Frequency (2400MHz)
Capacity of RAM. How
In all likelihood you know what is meant by capacity. The CORSAIR Vengeance LPX has acapacity of 8GB = 2³ x 2³⁰ bytes where 1 byte = 8 bits.
Take the capacity divide it by the width (64-bit word) and you will get the number of addresses. Every address contains a sequence of 1s and 0s which could represent an instruction (i.e. add) or an operand (i.e. the A in A+B).
Cell Type of RAM
RAM cells are volatile & different from others. When the power provided to a RAM cell is off, the stored data is lost forever. This is why when your computer isn’t responding, you can reboot it in order to reset it to a known state prior to having started any applications.
There are two mian types of RAM cells.
- Static RAM (SRAM) and Dynamic (DRAM).
- SRAM retains data bits in its memory as long as power is being supplied.
- Unlike DRAM, which stores bits in cells consisting of a capacitor and a transistor, SRAM does not have to be periodically refreshed.
- Static RAM provides faster access to data and is more expensive than DRAM. SRAM is typically used for cache whereas DRAM is used for main memory.
RAM Stick Type / Clock Frequency
Before we start going into the specifics, you need to know that DDR, DDR2, DDR3 and DDR4 are based off of SDRAM (Synchronous Dynamic Random Access Memory). By synchronous we mean that it is synchronized to the system clock. It means, the clock frequency of SDRAM must match the clock frequency of motherboard.
Engineers came up with a new technology solution known as DDR (Double Data Rate). A stick of DDR takes the motherboard speed and doubles it, it means transferring two data chunks per clock cycle. With each newly introduced subsequent, Each DDRx could transfer twice as much data in the same period of time than the previous one.
- DDR2 – bus clock x 2 x 2
- DDR3 – bus clock x 2 x 2²
- DDR4 – bus clock x 2 x 2³
Because of this naming convention, a stick of DDRx is labeled with double the real maximum clock rate at which it can operate.
For example, DDR4–1333 memories are compatible with motherboards that run at 666.6 MHz, DDR4–2400 memories are compatible with motherboards that run at 1200 MHz and so on.
RAM Clock rate & Slot Details
It is very important to know that the advertised clock rate is the theoretical maximum the memory can use. This does not means or guarantee that the memory will work at that speed.
For example, if you install DDR2 – 1066 MHz RAM on a computer that can only access the memory subsystem at 400 MHz (800 MHz for DDR2). The memories will be accessed at 400 MHz (800 for MHz DDR2) and not at 533 MHz (1,066 MHz for DDR2).
Alongside the advertised clock frequency, you’ll often see PCx-zzzz, where x is the technology generation and zzzz is the maximum theoretical transfer rate. Modern architectures have 64 lines going from a Memory Module to the Memory Controller on the Motherboard. This means 64 bits of data is transferred for every clock cycle. It means 8 bytes of data is transferred per clock cycle, Because 1 Byte is equals to 8 bits. So, If you take 64 bits & in converting into bytes you get 64/8=8 bytes. Multiply the clock frequency by the number of bytes (i.e – 8) and you will get the maximum theoretical transfer Rate in MB/s.
For example, DDR2 – 800 memories have a maximum theoretical transfer rate of 6,400 MB/s (800 x 8). Calculation, it transfers 8 bytes per clock cycle & it has 800 Clock Frequency.
Again, it is very important to understand that these transfer rates are the available bandwidth. When we calculate them, we are assuming that a data transfer will occur at each clock cycle, which in fact never happens because the CPU isn’t transferring data 100% of the time.
There are two main ways of determining your motherboard’s clock frequency.
What DDR Means?
Double Data Rate (DDR) RAM means that two transfers happen per clock cycle. Newer types of RAM are updated versions of the same technology, hence why RAM modules carry the label of DDR, DDR2, DDR3, DDR4 and so on.
While all RAM generations are exactly of the same physical size and shape, still they aren’t compatible. You cannot use DDR3 RAM in a motherboard that only supports DDR2 pin type configuration. Also note that DDR3 doesn’t fit in a DDR4 slot & vice versa . To avoid confusion, each RAM generation has a notch cut in the pins at different locations. That means you cannot plug any other RAM in that particular socket. So, it avoids accidentally mixing of your RAM modules & it prevents from damaging your motherboard, even if you buy the wrong type.
DDR2 is the oldest RAM you’re likely to come across today. It has 240 pins (200 for SO-DIMM). DDR2 has been well and truly superseded, but you can still buy it in limited quantities to upgrade older machines. Otherwise, DDR2 is obsolete.
DDR3 was released way back in 2007. Although it was officially supressed by later DDR4 in 2014. Still you will still find a lot of systems using the older RAM standards. The reason is DDR4 was not in usage until 2016. Two years after DDR4 launched DDR4 capable systems were not developed. Furthermore, DDR3 RAM covers a huge range of CPU generations, stretching from Intel’s LGA1366 socket through to LGA1151, as well as AMD’s AM3/AM3+ and FM1/2/2+. (For Intel, that’s from the introduction of the Intel Core i7 line in 2008 through to 7th generation Kaby Lake!)
DDR3 RAM has the same number of pins as DDR2. However, it runs a lower voltage and has higher timings (more on RAM timings in a moment), so aren’t compatible. Also, DDR3 SO-DIMMs have 204 pins versus DDR2’s 200 pins.
DDR4 hit the market in the year 2014, still it hasn’t taken complete control of the RAM market. Exceptionally high RAM prices slower down the upgrading process. But as the prices decreased, more people switched towards DDR4 RAM with the latest AMD and Intel CPU generations. That means if you want to upgrade to a more powerful CPU system, you will need a new motherboard and new RAM, too.
In DDR4 the RAM voltage drops even further, from 1.5V to 1.2V, while increasing the number of pins to 288.
DDR5 was targeted to hit consumer markets in 2019. But in real it takes few years for this technology to built its root. As sometimes people need to upgrade the whole system in order to get the best performance from the DDR5 RAM & only upgrading RAM won’t solve that purposes. As we know upgrading is li’l easier than switching it. Companies & Experts expect to hear more about it in 2020. RAM manufacturer, SK Hynix, expect DDR5 to make up 20% of the market in 2020, and 41% in 2021.
Identify the model number of your computer’s motherboard. Then search for the manufacturer and model number on the Internet. You will get the Detailed specs of the motherboard. That includes the front side bus (memory bus) speed, measured in MHz.
A number of software applications are available over the Internet that can tell you the speed of the front side bus. I will suggest you a freely available program that is really worthy, check this out – CPU-Z. CPU-Z provides detailed information about your computer, including the front side bus speed.
Download the software from here – CPU-Z
Multi Channel Memory Architectures
The multi channel architecture works on increasing the number of data lines available in the memory bus, thus it increases the available bandwidth.
1. Single Channel
In a single channel architecture, you have 64 lanes for connecting, memory modules to the memory controllers.
In a Two Channel Architecture, you have 2 x 64 = 128 lanes, it virtually doubles the available bandwidth.
Following the same logic, a three channel architecture would have memory bus 3 x 64 = 192 bits wide, a four channel would have a memory bus of 4 x 64 = 256 bits wide and so on.
It’s important to note that Two Channel Architeture requires two physical sticks of RAM.
If you say, you want to build a computer with 8GB of RAM. In order to achieve the best performance, you must buy two 4GB memory modules to enable the Dual Channel Mode, In it both RAM access Total 128 bits of data. If you buy a single 8GB module, you will have the same memory capacity but the memory will be accessed in the single channel mode, so only 64 bits will be used at a time.
2. Dual Channel
When you have more sockets than sticks of RAM, you have to make sure you install them in the correct memory sockets on your motherboard in order to get the maximum performance. If you have two RAM but not plugged in properly in the sockets, you will end up having a system accessing memory under a Single Channel Architecture.
In order to make it easier for all gamers & other users, most motherboard manufacturers use different colors for their memory sockets, for different channel mode. This way it makes easier & you just need to remember to install the memory modules in the sockets with the same color.
RAM – Speed, Latency, Timing
You’ve seen a lot of details & specs around SDRAM, DIMMs, and DDR generations.
But what about the other long strings of numbers in the RAM model means?
What is RAM measured in? And what about ECC and Swap?
Here are the other RAM specifications you need to know.
Clock Speed, Transfers, Bandwidth
You may have seen RAM referred to by two sets of numbers, like DDR3-1600 and PC3-12800. These both refer to the generation of the RAM and its transfer speed. The number after DDR/PC and before the hyphen refers to the generation: DDR2 is PC2, DDR3 is PC3, DDR4 is PC4.
The number placed after DDR refers to the number of MegaTransfers per second (MT/s). For example, DDR3-1600 RAM operates at 1,600MT/s.
The number placed after PC refers to the theoretical bandwidth in MBps. For example, PC3-12800 operates at 12,800MB/s.
How to Overclock RAM ? Is it Possible.
It is possible to Overclock RAM, just like you can overclock a CPU or graphics card. Overclocking increases the RAM’s bandwidth. Manufacturers sometimes sell pre-overclocked RAM. But you can easily overclock it by yourself. Just make sure that your motherboard supports the higher RAM clock speeds.
You might be wondering what happens when you mix RAM modules of different clock speeds.
When you mix two different RAMS of different clock speeds, Both will run at the clock speed of the slowest RAM Module. If you want to use the faster RAM, our suggestion is don’t mix it with your older or slower RAM module. Theoretically you can mix RAM brands of same specs, but it isn’t advisable. There will be a greater chance of encountering a blue screen of death or other random crashes when you mix RAM brands or different RAM clock speeds.
Timing and Latency
You will notice that RAM modules comes with a series of numbers, like 9-10-9-27. These numbers are preferred as timings.
A RAM timing is a performance measurement of the RAM module in ns (nanoseconds). The lower the numbers is, the quicker the RAM reacts to the requests.
In timing 9-10–9-27, the first number (9) is the CAS latency. The CAS (Column Access Strobe) latency refers to the number of clock cycles it takes for data requested by the memory controller to become available to a data pin.
Let us understand it using DDR3 and DDR4 as examples.
The lowest speed DDR3 RAM runs is 533 MHz, which means a clock cycle is of 1/533000000 or 1.87 ns (nanoseconds). With a CAS Latency of 7 cycles, Total Latency is 7 x 1.87 = 13.09 ns.
Whereas the lowest speed DDR4 RAM runs at 800MHz, which means a clock cycle of 1/800000000 or 1.25 ns (nanoseconds). Even if it has a higher CAS Latency of 9 cycles, Total Latency is 9 x 1.25 = 11.25 ns. That’s why it is faster than DDR3 RAM.
Mostly capacity trumps over clock speed and latency every time. You will get much more other benefits from 16GB of DDR4 -1600 RAM than 8GB of DDR4 -2400 RAM. In most of the cases, timing and latency are the last points of consideration before purchasing a RAM.
Error Correcting Code (ECC) RAM is a special kind of memory module that aims to detect and correct data corruption when heavy task is going on. Generally ECC RAM is used in servers where errors in critical data could be disastrous & create a huge problem. For example, personal or financial information that is stored in RAM while manipulating a linked database from servers.
Consumer Motherboards and Processors don’t usually support ECC compatible RAMs. Unless you are building a server in that scenario it specifically requires ECC RAM.
Final Thoughts on RAM
When your processor fetch data from secondary storage (i.e. HDD, SSD), it wastes few clock cycles that could have been spent on executing other instructions. The more RAM capacity you have means the more space you have to work with your processor, it results in less frequent accesses to secondary storage. The speed of RAM is relative to the memory bus. The advertised clock frequency is the theoretical maximum value & that can be achieved by using the right & standard hardware for standard given processes. If your processor and motherboard supports multi-channel architectures, you can significantly increase the available bandwidth by using multiple sticks of RAM on plugging it on proper socket of Mother board. This post encourage the readers to verify the architectures and clock frequencies supported by their motherboards, RAMS and memory controllers, In order to take full advantage of the available bandwidth.