Chapter 5 / Memory (RAM)

Resolving issues with newly installed memory (Tip# 1)

- 1. Verify the modules are seated correctly. a.) Remove and reinstall any new modules and make sure they sit in the socket at the same height as other modules. b.) Verify the support arms lock. If a support arm won't lock into position in the memory module, it is a sign that the module isn't seated in the slot properly.

System sluggishness & excessive hard drive accessing

- 2 symptoms that you need more RAM.

Resolving issues with newly installed memory (Tip# 2 & 3)

- 2. Verify you have installed the correct modules in the correct memory slots. 3. Try uninstalling the new modules and putting the old ones back in the system. If the problem goes away with the old modules: a.) Verify you purchased the correct memory for your motherboard. b.) Review your motherboard manufacturer's Website for BIOS updates. You might need to flash the BIOS to support new memory.

Soft error

- A data error that is not caused by a defective chip. - To avoid soft errors, usually safer to stick with the recommended or default refresh timing.

Blue Screen of Death (BSoD)

- A widely used term for the blue character-Mode screen that displays a stop or fatal error message, indicating that windows has become unstable and has stopped. - In Windows Vista and Windows 7.

General Protection Fault (GPF)

- An error caused when a Windows program accesses memory that another program is using. - Happens usually with Memory problems.

Motherboard Manuel or inside the case

- Best stop before upgrading RAM is:

DIMM (dual inline memory module)

- Can have memory chips on one or both sides of the package and supports 64-bit data transfer. - rated by the amount of memory they hold and by how fast they are. - Can have 168, 184, or 240 & 288 pins. - has a 64 bit data path. - most common type. - two rows of contacts

Single-channel memory bus

- Contains 64 wires & can transfer 64 bits of data to the CPU at one time. - You install memory modules individually.

200-pin SODIMM

- DDR laptop SO-DIMM is: - Half the size of DIMMs

200-pin SODIMM

- DDR2 laptop SO-DIMM is: - Incompatible with DDR SO-DIMM. - Half the size of DIMMs

204-pin SODIMM

- DDR3 laptop SO-DIMM is: - half the size of DIMMs

260-pin SODIMM

- DDR4 SODIMM is: - Half the size of DIMMs

Handling RAM

- DON'T EVER GRAB THE CONTACTS OF RAM.

Anything that interferes with refresh cycles causes:

- DRAM memory cell to lose the charge and thus the data, and if system is running it can lead to blue screens, global protection faults, corrupted files, and any number of system crashes.

latency

- Delay in RAM's response time is called: - measured in CL. - Example: CL6 is faster than RAM with a higher latency because it responds more quickly with less delay cycles. - Helps to decide between two similar stick of RAM.

Parity RAM

- Error-detecting RAM - replaced by the ECC feature. - contains one bit of memory for every bit of data it stores - 8 bits for each byte of data. - these memory modules have an extra bit that they use to verify each byte of data was correctly read or written by the memory module. • was the only way to tell if the RAM made a mistake. • used in servers not for public. • 2 types of parity: a 1 or 0. • wasn't perfect and it if it did find error it didn't correct it, just detect it.

Real Parity Errors / ECC error

- Errors that the MCC detects from the parity or ECC chips. - OS reports the problem in an error message in a hexadecimal value. - Always write down the value if you get an error like this. - shows up at the same place in memory each time and almost always indicates that you have a bad RAM stick.

CPUs and MCCs

- Example: a 400 MHz frontside bus speed wasn't achieved by making the system clock faster, it was done by making ______ and _____ capable of sending 64 bits of data 2 or 4 times for every clock cycle, doubling or quadrupling the system bus speed.

Extended Memory Profile (XMP)

- Feature of DDR3 ram, enables users to overclock RAM easily.

Windows memory diagnostic tool

- In Windows 7 and later, this tool can automatically scan your computer's RAM when you encounter a problem.

Serial Presence Detect (SPD)

- Information stored on a RAM chip that describes the speed, capacity, and other aspects of the RAM chip. - When a PC boots, it queries the SPD chip so that the MCC knows how much RAM is on the stick, how fast it runs, and other info. - CPU-Z can query the SPD chip.

non-maskable interrupt (NMI)

- Interrupt code (panic code) sent to the processor that cannot be ignored. - Sometimes triggered because of bad RAM. - Typically manifested as a BSoD (Proprietary Crash Screen).

Dynamic Random Access Memory (DRAM)

- Main system memory - needs a constant electric charge and periodic refresh (rewritten) of circuits. • stores data dynamically. - described by their width so we can call them x32 or x64. BE CAREFUL NOT TO DESCRIBE THEM BY CHIPS ON THE MODULE BUT KNOW IF PERSON IS TALKING ABOUT CHIP WIDTH OR MODULE. • info can be written to RAM repeatedly at anytime. • stores bits in cells consisting of a capacitor and a transistor. • Volatile • charge in tiny capacitors are constantly draining. • higher in density • sold in SIMM • operates Asynchronously with the system clock. / slower than system clock.

Memory Controller

- Memory type, speed, Max capacity of each module, and total memory capacity is defined by your computer's:

1-3x

- Microsoft recommends using ________ the amount of system RAM for the ReadyBoost drives or devices to get optimal performance.

(EDO) RAM - extended data out RAM

- Modified form of FPM memory. - Referred to as Hyper Page Mode. - Came in 72-pin SIMM form. - Consists of specially manufactured chips that allow timing overlap between successive accesses. - The data output drivers on the chip are not turned off when the memory controller removes the column address to begin the next cycle. - 5-2-2-2 burst mode. - Read in cycling time (ns).

manual

- Motherboard _____ tells you precisely what sort of module you need and how much RAM you can install.

slot

- Motherboards can be tricky and require you to install RAM in the proper slots to enable dual-channel memory access. - If you still get the same reading when you install a new stick, you should move one of the installed sticks to a different ________ to activate dual-channel memory and check the motherboard Manuel for the proper slots.

Dual-channel

- Never Mix DRAM stick speeds in the same bank with a motherboard that uses:

Triple-channel mode

- Not very common • MC communicate 3 DIMMs at a time. - tripled - Have 192 wires & must have 3 identical in threes.

How to dedicate ReadyBoast

- Plug a ReadyBoost approved device into the a USB port and the Right-Click the device in computer and select properties. - Click the ready boost tab and select the radio button next to either Dedicate this device to ReadyBoost or Use this device. - Click apply when done.

Memory chips or modules

- Primary active programs and data are stored in:

POST

- RAM Stick with a bad SPD chip will give you a ______ error message and the system will not boot. - Can't fix a bad SPD so you have to buy a new stick.

modules or packages or stick

- RAM is connected to the MB through:

Memory Bus

- RAM is connected to the Northbridge chip (memory controller) through the ________ on the MB. - is a series of electronic circuitry that provides 3 functions.

Logical mapping and layout

- Refers to how the memory addresses are mapped to actual chips and what address locations contain which types of system information.

Phantom Parity errors

- Shows up on systems that don't have parity or ECC memory. - If windows displays parity errors with different addresses, you most likely do NOT have a problem with RAM. - can occur because of software problems, heat or dust, solar flares and etc.

Data, address, & control

- The 3 functions of the memory bus are:

1.5 times

- The default and recommended page-file size in Windows is ______ times the amount of installed RAM on your computer.

pagefile.sys

- The page file is: - you can find it in the root directory of the C: drive. - it is a hidden system file.

RAM

- The program can't actually run from the page file; it must be loaded back into:

tREF

- The time between refresh cycles in memory is known as _______ AMD is expressed in clock cycles. - Can be altered via CMOS Setup. - Increasing the time between refresh cycles to speed up system can allow memory cells to begin draining prematurely and causes soft memory errors.

Burst mode cycling

- This type of cycling take advantage of the consecutive nature of most memory accesses. • after setting up the row and column accesses for a given access, you can then access the next three adjacent addresses with no additional latency or wait states. • limited to 4 total accesses. • expressed as x-y-y-y; • x = time for the first access (latency plus cycle time). • y = number of cycles required for each consecutive access.

page file or swap file

- Virtual memory is a portion of a hard drive or solid state drive set aside as what's called a: - when computer starts running out of real RAM because of the many loaded programs, the system swaps programs from RAM to the ________ file, opening more space for programs currently active. - works like a temporary storage box.

SIMM, DIMM, & SODIMM

- What are the 3 types of modules that RAM can be connected to: - each module type you can have is dictated by the slots on your MB.

Real and phantom parity errors

- What are the two different kinds of parity errors?

System Lockup

- When the computer stops functioning this is called a:

Blue screen with a sad face and the words to the effect of Windows

- Windows 8/8.1/10 has a crash screen that looks like:

What happens when you click on a page file.

- Windows decides which program must be removed from RAM and this time windows chooses Program C. - Then it loads program B into RAM. - Swapping programs to and from the page file and RAM slows your computer down and takes time.

ReadyBoost

- Windows feature enabling the use of flash media as dedicated virtual memory. - preferred over virtual memory because hard drives take forever. - Even better when you have multiple sources of virtual memory that it can use at the same time.

Mixing speeds

- You can use RAM that is faster than the motherboard specifies. - Faster DRAM is not going to make the system run any faster. - you can get away with putting one speed of DRAM in one bank and another speed in another bank as long as all the speeds are as fast or faster than the speed specified by the motherboard.

full bank

- You need to install w sticks of RAM to make a _______ because each stick only provides half the bus bandwidth.

The data bus

- carries that data to be read or written by the CPU.

Unbuffered DIMM or RAM

- communicates directly with the Northbridge chip or the CPU.

Intermittent memory errors can come from:

- dying power supply, electrical interference, buggy applications, buggy hardware. - Errors show up as lockups, general protection faults, page faults, and parity errors. - always look at power supply first when these errors happen.

ECC (error correction code) Memory

- include a parity bit, but they don't use single-bit parity checking and instead use the ECC module uses an algorithm to encode information in a block of bits it uses to detect both single-bit and multi-bit errors. - ECC modules can use this info. to correct single-bit errors. - ECC algorithm causes a slight slowdown in system operation as it checks memory for error. • detects any time a single bit is incorrect. • fixes these errors on-the-fly. • you know if it has ECC by count. • non ECC has 8 memory chips. • ECC has 9 memory chips. • most RAM modules today are non-ECC. • typically used in servers because they need to be running at all times. / protection for memory errors. • not for public and slow. • MB has to be designed for it.

SIMM (single inline memory module)

- is a an older technology circuit board where multiple DRAM chips are attached to the circuit board. - has memory chips on one side of the package. • has a 32 bit data path - had wider DRAM chips such as x4, x8, x16 and x32. - need right stick or sticks for motherboard. • one row of electrical contacts.

CAS (Column address (or array) strobe) latency, abbreviated CL

- is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM module, and the moment the data from the given array location is available on the module's output pins. • Related to speed and sometimes called read latency. • The number of clock cycles occurring between the registration of the CAS signal and the resultant output data, with lower numbers of cycles indicating faster (better) performance. • CL read by MB chipset are of the SPD (serial presence detect) ROM on the module to take advantage of lower latency through improved memory controller timings.

How virtual memory works

- it starts by creating a page file that resides somewhere on your hard drive and then Windows removes running programs temporarily from RAM into the page file so other programs can load and run. - to load, program D needs a certain amount of free RAM which requires unloading some other program or programs from RAM without closing the program(s). - Windows decides which is the least program used and that program is then cut out of or swapped from RAM and copied into the page file. - Unloading program B from RAM provides enough RAM to load Program D.

DDR memory

- memory type based on the SDRAM technology that uses the memory bus clock signal to synchronize with the system bus clock speed. - uses both the rising and falling edge of the clock signal to send data which allows 2 pieces of data per clock cycle.

Page Fault

- minor error that can be caused by memory issues but not necessarily system RAM problems.

Troubleshooting memory problems

- some memory errors could be because of underpowered memory or failing power supply, your computer is overheating, or a bad memory module. 1. Verify your power supply is functioning properly. 2. Verify your system is not overheating. 3. Clean memory module edge connectors and slots. a.) Remove the memory modules. b.) Clean the edge connectors with a soft cloth or contact cleaner. c.) Using compressed air or a computer vacuum, remove dust and debris from the slots. d.) Reinsert the clean modules. 4. Swap the memory modules one at a time with a "Known Good" module. 5. If your BIOS/UEFI includes a hardware diagnostic feature, run the memory check. 6. Run a third-party program that checks for problems with computer hardware.

The address bus

- specifies the memory address where the CPU should retrieve the data from or write the data to. - when the CPU needs certain bytes of data, it requests those bytes via:

The control bus

- tells the memory module if the operation is a read or write. - Carries commands from the CPU and returns status signals from the devices. - also contains circuitry that specifies the memory's clock signal.

memtest86+

- this software exhaustively checks your RAM and reports bad RAM when it finds it.

Buffered RAM (registered RAM)

- uses buffers (Buffered DIMM) to hold data and manage electrical signals before the information passed between the memory chip and the Northbridge chip (memory controller) or CPU if there is no Northbridge chip. • is made to add stability to RAM. • adds an extra register between the RAM and the memory controller. • stores (buffers) data before it gets sent to the CPU. • adds stability and reliability in computer systems that have a lot of memory modules installed. • lessens the electrical load on your memory controller used when you use a lot of memory modules. • used mainly in servers.

disk thrashing

- when computer frequently accesses the page file, you will notice access LED going crazy as Windows rushes to move programs between RAM and the page file in a process called: - This suggests that you need more RAM.

Virtual Memory

- when computers use a portion of the hard drive as extension of system RAM, through what's called:

DDR2 Module (240-pin DIMM)

1. Chip type - DDR2-400, base clock speed 100MHz, cycles per clock 2, so 400MHz X 8 = PC2-3200. - get DDR-400 because base clock is 100MHz x DDR of 2 = 200 MHz then you multiply I/O speed by 2 which = 400 MHz DDR2 speed. 2. Chip type - DDR2-533, base clock speed 133 MHz, cycles per clock 2, so 533MHz X 8 = PC2-4200 - get DDR-533 because base clock is 133 MHz multiplied by 2 cycles per second = 266 multiplied by I/O speed by 2 which = 533 MHz DDR2

DDR SDRAM module (184-pin DIMM)

1. Chip type - DDR200, base clock speed 100MHz, cycles per clock 2, so 200MHz X 8 bytes = PC1600. 2. Chip type - DDR266, base clock speed, 133MHz, cycles per clock 2, so 266MHz X 8 bytes = PC2100

SRAM

Built into MB

DRAM

Normally need to purchase and install in a system

What are the 3 varieties of the SDRAM Module 168-pin DIMM?

PC stands for Mother Board type. Used clock speed as it's label name like PC66. 1. PC66, 66MHz, 8 byte wide bus, could transfer 66MHz X 8 bytes = 528 MBps. 2. PC100, 100MHz X 8 bytes = 800 MBps 3. PC133, 133MHz X 8 bytes = 1,066 MBps

RAM formula

RAM = Bus speed X Clock Multiplier X 8 bytes = throughput or bandwidth. • clock multiplier is 2 for DDR power.

DDR4 Module (288-pin DIMM)

• DDR4 modules are both physically and electronically incompatible with previous memory module and socket design. 1. Chip type - DDR4-1600, Base Clock Speed 200 MHz, Cycles per Clock 2, so 1600MHz X 8bytes = PC4-12800 MBps. - Get DDR4 because 200 MHz base clock speed x 2 for double date = 400 MHz x I/O from DDR 2 = 800 x I/O from DDR 3 = 1600 DDR4.

Single sided RAM vs. Double sided RAM

• Doesn't necessarily refer to the physical location of the memory chips that are on the sides of the memory module. • refers to the groups of memory chips that a memory controller accesses. • example: double-sided RAM has 2 groups of memory chips. • Double sided memory means that the memory controller sees these two groups of memory chips separately. / can only access it one group at a time. • Single sided RAM has one group of memory chips. Can be on one side or both sides. • With single sided RAM, the memory controller can access it as one group which makes single sided RAM faster than double sided RAM.

Micro-DIMM

• Electrical contacts are different on each side • DDR SDRAM - 172 pins • DDR2 and DDR3 SDRAM - 214 pins

Synchronous DRAM also called (SDR) or single data rate

• JDEC std for type of DRAM that runs in synchronization with the memory bus or system clock. - MCC knows when data is ready to be grabbed from SDRAM. • delivers info in high speed bursts using a high-speed clocked interface. • removes most asynchronous DRAM latency because signals are already in synch with the MB clock. • burst access to 5-1-1-1. • sold in DIMM form • rated by clock speed (MHz) rather than cycling time (ns). • came in 168-pin DIMMs. • 1 transfer per clock cycle

DDR SDRAM (double data rate SDRAM)

• Sends double the amount of data in each clock signal. - Signals in sync with with memory bus clock. • uses rising and falling edge of clock signal to send data which makes It twice as fast. • 2 transfers per clock cycle. • uses DIMM module design with 184 pins. • uses the total bandwidth in its label name. • support dual channel operation - technique in which 2 matching DIMMs are installed to function as a single bank, with double the bandwidth of a single module. • your okay installing module that is faster than system requirements. • never go lower

fast page mode (FPM)

• Standard DRAM memory • paging enables faster access to all the data within the given row of memory by keeping the row address the same and changing only the column. • eliminated one cycle at a time. • 5-3-3-3 burst mode. • read in cycling time (ns).

Dual-channel operation

• Technique in which two matching DIMMs are installed to function as a single bank, with double the bandwidth of a single module. • in this mode the bandwidth doubles. • optimizes PC design by ensuring that the CPU bus and memory bus both run at the same speeds meaning throughput so that data can move synchronously between the buses without delays. • requires pair of identical DIMMs. •allows memory controller the ability to communicate with 2 DIMMs simultaneously. • MB must be equipped to work in this mode. • DIMMs must be identical in speed, size, and features. • DIMMs must be inserted into MB in a specific slot configuration / color coded pairs. • transfers 128 bits of data at a time / 16 bytes • enabled in the BIOS and make single bank.

DDR2 SDRAM

• achieves higher throughput by using differential pairs of signal wires to allow faster signaling without noise and interference problems. - the big increase comes by clock doubling the input/output circuits on the chips. • DDR2 DIMMs have 240 pins • higher bus speeds / less power than DDR

RDRAM (rambus dynamic random access memory)

• developed RIMM -Rambus In-line memory module. • Has 184 pins / look similar to DIMMs / bottom notches located in the center of the Module. • fallen behind because of DIMMs. • speed was 800MHz / only had 2 byte wide bus. • designed to work with continuous signal / meaning all slots on MB had to be in use to work. • If other RIMMs were not available because it requires two and expensive then user can install a C-RIMM: continuity RIMM (dummy RIMM) instead of RIMMs to ensure continuity. Called terminator stick also. • proprietary. / ram fast and hot. / required install in pairs. • has heat shield.

DDR3 Module (240-pin DIMM)

• enables higher levels of performance with lower power consumption and higher reliability than DDR2. - Doubles the buffer of DDR2 from 4 bits to 8 bits and uses higher-density memory chips. - supports triple-channel or quad-channel architecture. • slot location is what is different between DDR-2 & DDR-3. 1. Chip type - DDR-800, Base clock speed 100 MHz, Cycles per clock - 2, so 800MHz X 8 bytes = PC3-6400 MBps - get DDR-800 because base clock is 100 MHz multiplied by 2 cycles per second = 200 MHz x I/O from DDR2 = 400 MHz x Double the buffer from DDR3 = 800 MHz DDR 3

SODIMM (small outline dual in-line memory module)

• laptop memory DIMM Module and also used for mobile devices.

Memory (RAM)

• workplace for the processor • temporary storage area where pgms & data being operated on by processor must reside. • data & pgms remain as long as their is electrical power. - VOLATILE • usually called Random Access Memory (RAM).