Chp.4 RAM

Chp.4 RAM

1. Types of RAM

   • Static random-access memory(SRAM)
     • its contents does not need to be periodically refreshed
     • used in cache memory
     • used as buffers for motherboards and Hard drives
     • used as temporary storage for LCD screens
   • Dynamic RAM (DRAM)
     • memory contents needs to be refreshed
       • the act of reading information from a specific area of memory and immediately rewriting that information to same are without modifying it
     • every bit of info is stored in capacitors
       • lose charge over time, hence to need to be refreshed
     • referred to as memory modules

2. Different types of DRAM

   • Synchronous DRAM
     • synchronized to the base clock of the mothernboard
       • referred to as system bus speed
     • typical clock rates are 66, 100, and 133 MHz
       • referred to as PC66, PC100, and PC133
     • designed as a 168-pin DIMM
       • Dual in-line memory module
         • successor to the SIMM
           • the difference between the two are
             • DIMMs have separate electrical contacts on each side of the module
             • SIMMs might have contacts on both sides, but they are redudant
     • generally has a bus width of 64 bits (8 bytes)
   • Double Data Rate (DDR)
     • synchronized to the memory clock
       • like SDRAM
     • SDRAM that has been double-pumped
       • twice the data transfer at same clock speed
         • does this by transferring data on the rising and falling edges of each clock cycle
     • equation for data transfer rate (bandwidth)
       • clock speed x bytes x 2 = data transfer rate
     • easier way to solve data transfer rate
       • 400 megatransfers/s x 8 = 3,00 MB/s
   • DDR 3
     • faster and more efficient than DDR 2
     • code meaning on module
       • KVR1333D3N9HK2/8G and kit of 2, 1.5V
         • DDR3-1333 RAM
         • 8 GB
         • 2 modules that run at 1.5 Volts
   • DDR 2
     • faster than DDR
     • standard 240 pins

3. RAM Technologies

   • Single channel
     • original RAM architecture
     • a 64-bit bus (or data channel) between the memory and memory controller
   • Dual channel
     • two separate 64-bit channels are employed together resulting in a 128-bit bus
   • Triple channel
     • accesses three memory modules at the same time, in effect a 192-bit bus
   • Memory Latency
     • or Column Address Strobe (CAS) latency
     • happens when a memory controller tries to access data from a memory module
       • there is a slight delay (measured in nanoseconds
       • it is given a CAS or CL rating
         • the higher the CL number, the longer the delay
   • Single-sided
     • refers to a memory module with a single "bank" of chips
       • the memory controller can access all the chips at once
   • Double-sided
     • has their chips divided into two "sides" known as banks
       • only one "side" can be seen by the computer at a time
   • Parity
     • RAM parity is when memory stores an extra bit (known as parity bit) used for error detection
       • can store 9 instead of 8 bits for every byte of data
   • Error Correction Code (ECC)
     • can detect and correct errors
     • slowest and most expensive of RAM types
   • Registered memory
     • improves the integrity of the signal between RAM and the memory controller by electrically buffering the signals using an extra register
       • done for stability
   • Fully buffered memory
     • introduces an advanced memory buffer between the memory controller and the memory module

4. Installing

   • select correct module
     • employ ESD prevention methods
       • ready the motherboard
         • install the RAM
           • test the installation
             • BIOS POST, System properties, Task manager

5. Troubleshooting DRAM

   • make sure RAM is fully seated
   • Check big four
   • RAM can manifests itself as intermittent problems caused by ESD
   • computer will not boot/intermittently shuts down
     • damaged or not secure RAM can prevent computer form doing anything at all
     • POST card and/or replace RAM with good one
     • RAM can overheat and cause intermittent shutdowns
       • heat sinks made of aluminum and copper can be added to RAM.,
         • known as heatspreaders
   • BIOS,Page faults, BSOD and General protection faults
     • BIOS
       • can indicate a error through gray message of beeping
         • BIOS can have incorrect settings
         • BIOS doesn't programming necessary to identify RAM
           • Flash BIOS
     • BSOD (Stop error)
       • can be due to device driver errors or a physical fault in memory
         • can Be an nonmaskable interrupt, interrupts CPU to nonrecoverable hardware errors
           • write down info and cross reference it on MSoft support website
     • Page faults
       • can be an OS issue or app that was running
         • if particular app keeps failing, or you get a specific memory location over, and over it could be RAM
     • General protection faults (GPF)
       • can cause a program to fail
         • in old Windows it would case entire OS to shut down
           • displays a black screen