Form factor
A parameter that determines the physical dimensions of the memory module, as well as the number and arrangement of pins on it. To date, the most popular form factors are:
—
DIMM. Classic full-size memory sticks, used mainly in desktop PCs. The number of contacts is usually between 168 and 240.
-
SO-DIMM(Small Outline Dual In-Line Memory Module). A smaller version of the DIMM form factor designed for use in portable computing equipment such as laptops and tablet PCs. The number of contacts varies from 72 to 200.
-
FB-DIMM(Fully Buffered Dual In-Line Memory Module). Memory modules with increased reliability due to the use of a buffer in the design (see Buffering support (Registered)). Most often used in servers. Similar in appearance to 240-pin DIMMs, but not compatible with them.
CAS latency
This term refers to the time (more precisely, the number of memory cycles) that passes from the processor's request to read data to granting access to the first of the cells containing the selected data. CAS latency is one of the timings (for more details, see the "Memory Timings Scheme" section, where this parameter is designated as CL) — which means that it affects performance: the lower the CAS, the faster this memory module works. However this is true only for the same clock frequency (for more details, see ibid.).
Now there are memory modules on the market with the following CAS latency values:
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20,
21,
22,
24,
30,
32,
36,
38,
40,
42,
46.
Memory timing
Timing is a term that refers to the time it takes to complete an operation. To understand the timing scheme, you need to know that structurally RAM consists of banks (from 2 to 8 per module), each of which, in turn, has rows and columns, like a table; when accessing memory, the bank is selected first, then the row, then the column. The timing scheme shows the time during which the four main operations are performed when working with RAM, and is usually written in four digits in the format CL-Trcd-Trp-Tras, where
CL is the minimum delay between receiving a command to read data and the start of their transfer;
Trcd — the minimum time between the selection of a row and the selection of a column in it;
Trp is the minimum time to close a row, that is, the delay between the signal and the actual closing. Only one bank line can be opened at a time; Before opening the next line, you must close the previous one.
Tras — the minimum time the row is active, in other words, the shortest time after which the row can be commanded to close after it has been opened.
Time in the timing scheme is measured in cycles, so the actual memory performance depends not only on the timing scheme, but also on the clock frequency. For example, 1600 MHz 8-8-8-24 memory will run at the same speed as 800 MHz 4-4-4-12 memory—in either case timings, if expressed in nanoseconds, will be 5-5-5-15.
Voltage
The nominal voltage required for the operation of the memory module. When choosing memory, you must pay attention to the fact that the appropriate voltage is supported by the motherboard.
Cooling
Type
of cooling provided in the design of RAM.
—
No refrigeration. The lack of special cooling is typical for memory modules with low and medium power — they do not emit so much heat that it needs to be specially removed.
— Radiator. A device in the form of a metal structure with a characteristic ribbed surface — this form increases the area of \u200b\u200bcontact with air, which, in turn, improves heat transfer. The simplest type of cooling system is inferior in efficiency to a radiator with a cooler and even more so to a water circuit (see below), but it does not create noise, does not consume excess energy and does not require additional power or tubes. And the mentioned efficiency is enough even for quite powerful RAM modules.
— Radiator with cooler. Radiator
cooling(see above), supplemented by a block with a fan (fans) for forced air circulation. This add-on significantly increases the efficiency of the heatsink; it can be used even in fairly powerful RAM sets. On the other hand, the fan creates noise during operation and significantly increases power consumption.
— Water cooling. Cooling in the form of a liquid heat exchanger connected to the water cooling circuit of the computer system. A distinctive external feature of such cooling are two characteristic pipes. Water systems are very efficient and suitable even for the mo
...st powerful and “hot” sticks, but they are difficult to connect and require expensive external equipment, and therefore they are mainly used among top RAM models, in which such cooling is in principle indispensable. Note that some of these models allow operation “dry”, without water, but this is not recommended — failures may occur at high loads.
— Liquid-air. In accordance with the name, this option involves the use of two types of cooling at once — air (radiator) and water. See above for both, but it is worth noting that in this case water cooling can be provided in a somewhat “truncated” form — not in the form of pipes for connecting to a common cooling circuit, but in the form of a sealed capsule with a heat-conducting liquid. In terms of efficiency, such systems, of course, noticeably lose to classical liquid ones — but they do not require complex connections; and the capsule somehow improves the efficiency of the radiator, and it looks unusual.
