CIS 1110A - Computer Operating Systems and Maintenance


Module 3

This lesson discusses processors and memory. Objectives important to this lesson:

  1. Intel and AMD processors
  2. Selecting and installing a processor
  3. Types of memory
  4. Replacing memory
  5. Current assignments

Concepts:

A discussion of the Central Processing Unit (CPU) opens this chapter. CPUs have been around long enough that they are more commonly just called processors. Features of CPUs that are used to rate and compare them are discussed. This is this year's list:

  • Processor speed - measured in megahertz (MHz) or gigahertz (GHz). (Mega means million, giga means billion. Hertz means cycles per second.) The text tells us this is also called the processor frequency.
  • Lithography - sounds like it concerns measuring stones: in a way it does; this is a measure of how close together (measure) transistors can be on a processor chip (slice of stone); smaller numbers mean more transistors in a smaller space (see Moore's Law): the text tells us that processors typically have 14 to 35 nanometer separation between transistors
  • Socket and chipset - what socket does a processor require, and what chipsets can it use? This will tell you if you can swap out a new processor for the one currently installed on a motherboard.
  • Multiprocessing ability - can the processor do more than one task at a time? It must have two or more Arithmetic Logic Units (ALUs) to do so.
  • Multi-threading - a thread is typically a series of processing steps; a multi-threading processor can handle more than one thread at the same time by operating as two logical processors, kind of like running a virtual machine in a good computer
  • Multicore construction - this is the most recent of the three options in the text: the processor is actually a housing for several real processors, each of which is called a core; as the text explains, if a processor has four cores that each can process two threads, it could handle eight threads at once
  • Multiprocessor motherboards - the text mentions server motherboards that can have two processors, which does not sound impressive until you consider that each of them can have a abilities in the three bullet notes above

  • Internal and external cache - A cache built into the processor (actually on the chip) is called internal cache, primary cache, level 1, or L1 cache. External cache (in the processor module but not on the chip) is called secondary, level 2, or L2 cache. The larger each is, the better.
  • Word size (internal data path size) - Dr. Andrews does not use this term, but it still means how many bits the processor handles at once. Most processors are 32 bit or 64 bit, but some hybrid processors can run as either.
  • Data path (external data path) - 8 to 64 bits (currently), the number of bits that can be sent to the CPU at once. The data path size and word size are not necessarily the same.
  • Kind of RAM, maximum number of memory addresses this CPU can manage, chip sets, and motherboards the processor will work with.

Intel processors used to have simple names (286, 386), then they got more creative names (Pentium) , and now they are grouped into generation sets, such as 7th and 8th generation, but they also categorize them as Core i8 and Core i9, which does not mean the same thing.

AMD processors are both less and more confusing. Let's listen to a kind gentleman who wants to speak about both brands.


Okay, so he tells us a lot. Some chips have graphics ability included, but gamers should still install graphics cards. The Intel Core iNumber notation does not tell us how many cores we get, only that a bigger number means it's better than one with a smaller number, but only within the same generation. Sort of. AMD notation is similar, but not clearer. Consider the Applying Concepts exercise on page 124. It shows that there are often many choices, each with different prices and performance features. Making choices in computer parts often comes down to what it is expected to do and how much can be spent to do it.

The text gives us a few pages on installing a new Intel processor, an AMD processor, and installing a cooling assembly on each. Note the use of thermal paste on top of the processor to conduct heat to the cooler. Failing to do so can lead to unpleasant results.


We do not recommend cooking on a processor: it ruins the food and the processor.

RAM (Random Access Memory) has come in several sorts of packages. Some RAM chips were soldered onto motherboards in the early days, or on expansion cards. RAM that is meant to be replaced by the user is more often contained on a SIMM (Single Inline Memory Module) or a DIMM (Dual Inline Memory Module). SIMMs will only be found in older computers now. They had chips on one side of a small card, while DIMMs typically have chips on both sides of the card. DIMMs also have little notches in their connectors, to identify whether they use 3.3 volts or 5 volts, and to identify them as registered (RFU), buffered, or unbuffered. Different systems will require different DIMMs. Laptops and small form factor devices may require SO-DIMMs, which are Small Outline DIMMs. They fit smaller slots, and take up less space.

DIMMs can be either DRAM (dynamic) or SRAM (static). The word static is misleading here. DRAM chips need to have their data refreshed dynamically every few milliseconds (often, every 4 milliseconds) with a jolt of power. SRAM chips do not need to have this periodic jolt, and will retain the data placed on them without the jolt, but only until the computer's power is turned off. In this respect, DRAM and SRAM chips will both lose their data when the computer is turned off. SRAM chips are more expensive, but give faster access, so they are used where this speed advantage is necessary.

The text lists several generations of DIMMs, starting with DDR (Double Data Rate) DIMMs, which could be read twice in a motherboard's clock cycle instead of once. This technology was followed by DDR2, DDR3, and DDR4, each of which is faster than its predecessor. Note the illustrations on page 138:

  • DDR2 - 240 pins in the motherboard connector (the "pins" look more like flat metal strips)
  • DDR3 - 240 pins
  • DDR4 - 288 pins

DIMMs can support dual, triple, and quad channeling, which allows the system memory controller to read two, three, or four DIMMs at the same time.

  • When doing this, make sure that the DIMMs to be read at the same time are of the same type and brand. If the memory controller does not see them as the same, it will only use single channeling.
  • If your motherboard supports DDR3, you should see three DIMM slots of one color. Populate all three. If there, is a fourth slot, using it may cause the memory controller to go to single channel mode.
  • A motherboard that supports DDR4 should have eight DIMM slots, two for each channel. Implementations vary, so check user/service manuals.

Memory comes in various speeds, measured in several ways. Some older memory was measured in nanoseconds (ns). A nanosecond is one billionth of a second. To picture it, electricity travels 11.78 inches along a copper wire in a nanosecond. In a microsecond (one millionth of a second), it travels 984 feet. (For readers outside the United States, these measurements are in US terms. The words millionth and billionth can have different meanings elsewhere. See the discussion of nanosecond on WhatIs.com.) If memory is rated at 70 nanoseconds (ns), it is slower than memory rated at 60 ns. Smaller numbers are faster.

DDR memory is measured differently. It is rated in MHz, or in a PC rating. For example, a MHz rating may state that the RAM is capable of running at 333 or 400 MHz. A PC rating will tell us the throughput of the module, in round numbers. A module that can process 64 bits at a time is processing 8 bytes at a time. We multiply the 8 bytes times the MHz rating of the module to get a PC rating: a module rated at 400 MHz times 8 bytes gives us a PC rating of PC3200.

DIMMs can be parity, ECC, or non-parity/non-ECC.

  • Parity systems store an extra bit for every byte, recording that the number of 1s in the byte is even or odd. This allows the DIMM to check the data written to it when it is read later.
  • ECC (Error Correcting Code) DIMMs will have an extra chip on the module. The error trapping is more advanced than parity, in that it allows the DIMM to correct a misread of a single bit.
  • non-parity/non-ECC DIMMs do not do error trapping. They are not recommended for servers.

DIMMS can also be registered, buffered, or unbuffered. A buffer and a register are the same kind of thing, a temporary holding area. They just use different technology. Each holds an incoming signal and amplifies it before writing to the DIMM, making it more reliable.

Memory can also be measured and rated by its latency. In general, latency means "how long do we have to wait?" How long does it take to actually read or write to the module? Not a long time, to be sure, but the lower the latency rating, the faster the memory is. It may be expressed as column access strobe (CAS) latency or row access strobe (RAS) latency. They refer to the number of clock cycles it takes to read or write a column or row of data in the memory module.Obviously, low latency is better than high latency.

Adding and upgrading RAM are discussed. The author presents a list of questions that should be answered before buying RAM:

  • How much memory do I need?
  • How much memory can my computer physically accommodate?
  • What increments of memory does my system board support?
  • What kind of memory can fit on my system board?
  • What memory is compatible with the memory I already have installed?
  • How do I remove and install the memory modules?
Adding RAM can be tricky. If the system misbehaves after changing the installed RAM, check all the factors. Is it physically installed correctly? Does the BIOS recognize it? Did you buy the right kind? Have you put more memory on the motherboard than it can address? Any of these problems will lead to a computer that does not work.

Assignments

  1. Read the chapter, and the next one for next week.
  2. Complete the assignments and class discussion made in this module, which are due by 6pm next week.