Chapter 6 Memory and Floppy Drives

You Will Learn… About the different kinds of physical memory and how they work How to upgrade and troubleshoot memory How floppy drives work and how to support them

Physical Memory ROM  Retains its data when PC is turned off  Stores data on chips socketed or soldered to circuit boards RAM  Loses its data when PC is turned off  Two categories Static RAM (SRAM) Dynamic RAM (DRAM)

Dynamic RAM

ROM on the Motherboard ROM chips (aka firmware)  Permanent programs EPROM (erasable programmable ROM)  Programs can be changed EEPROM (aka flash ROM chips)  Programs can be changed

ROM on the Motherboard

Flash Memory Makes it possible to replace programming on a chip rather than replace the chip itself Acts more like secondary storage; does not lose its data when power is turned off Holds data electronically; provides faster data access than mechanical device, but more expensive Uses EEPROM chips

RAM on the Motherboard

SRAM on a Motherboard

How SRAM Is Used in Different Memory Caches

How Memory Caching Works

Static RAM Technologies Synchronous SRAM  Requires clock signal to manage or synchronize its control signals; cache memory can then run in step with CPU  Can be either burst or pipelined burst SRAM Burst SRAM  Data is sent in a two-step process: first the data address, then a series of data transmissions continued…

Static RAM Technologies Pipelined burst SRAM  Uses more clock cycles per transfer than burst SRAM without pipelining, but is less expensive Asynchronous SRAM  Does not work in step with CPU clock; unable to process as much data in one request; overall slower memory access Housed within the processor (new trend)

SRAM on the Motherboard Current systems generally include all SRAM needed for optimum performance With older system, might be less expensive to replace motherboard than to upgrade cache

Dynamic RAM Technologies Physically housed on:  SIMMs (single inline memory modules)  DIMMs (dual inline memory modules)  RIMMs (inline memory modules by Rambus, Inc.) Main differences in the three:  Width of data path that each type of module accommodates  Way the data moves from system bus to module Goal is to increase overall throughput while retaining accuracy

Types of RAM Modules

SIMM Technologies First used FPM (fast page mode) memory, then EDO (extended data out) memory Rated by speed, measured in nanoseconds

DIMM Technologies Rated by speed and amount of memory they hold First used EDO or burst EDO (BEDO), then used synchronous DRAM (SDRAM) technology

DIMM Technologies

Synchronous DRAM Currently most popular memory type Rated by system bus speed Operated in sync and at same speed as system clock Comes in three variations  Regular SDRAM  DDR SDRAM (SDRAM II) – most popular  SyncLink (SLDRAM)

RIMM Technologies Used by Direct Rambus DRAM Each socket must be filled to maintain continuity  If not filled, socket must hold a placeholder called a C-RIMM (Continuity RIMM)

RIMM Technologies

Parity Older method of testing integrity of bits stored in RAM or secondary medium, or bits sent over a communications device

Error Checking Error-correcting code (ECC)  Current method used to detect and correct an error in a single bit

Upgrading Memory Adding more RAM to the computer What to look for when buying memory chips and modules How much and what kind of memory to buy

What to Look for When Buying Memory Chips and Modules Use fastest memory motherboard can support Match method of memory detection used by the module to what the motherboard expects Use memory type recommended by manufacturer Match tin leads to tin connectors and gold leads to gold connectors to prevent corrosion Date stamps on remanufactured and used modules should be relatively close together Beware re-marked chips

How Much and What Kind of Memory to Buy Use type, size, density, and speed of memory the motherboard supports Match memory modules already installed

How Much Memory Can Fit on the Motherboard? Use right number of SIMMs, DIMMs, or RIMMs with right amount of memory on each module to fit memory banks on motherboard  30-pin SIMMs  72-pin SIMMs  DIMMs  RIMM modules

DIMMs

RIMMs

Reading Ads About Memory Modules The number of pins, the speed, the size, and the type of module are all important

Installing Memory For most SIMMs, the module slides into the slot at an angle For DIMM modules, small latches on each side of the slot hold module in place For RIMM modules, remove the C-RIMM (if present) and then insert the RIMM in the slot

Installing a SIMM Module

Installing a DIMM Module

Troubleshooting Memory If computer does not recognize new SIMMs, DIMMs, or RIMMs, or memory error messages appear If memory errors occur during normal operation, and you have not just upgraded memory

Floppy Drives How data is stored—physically and logically How to manage the data How to install a floppy disk drive on a PC

Physical Data Storage on a Floppy Disk

Floppy Drive Subsystem

Physical Data Storage on a Floppy Disk Disk must be formatted (process of marking tracks and sectors to prepare disk to receive data)

Physical Data Storage on a Floppy Disk Data is written to and from the disk via a magnetic read/write head

Physical Data Storage on a Floppy Disk

Logical Data Storage on a Floppy

Formatting Process for a Floppy Creates tracks and sectors Creates boot record Creates two copies of file allocation table (FAT) Creates root directory

The Boot Record

The Root Directory Table

Using Commands to Manage a Floppy Disk Format Drive: /S /V:Volumename /Q /U /Autotest  Used to format a disk or hard drive  /S option makes a drive bootable Chkdsk [drive:] /F /V  Checks drives for errors and repairs them

Options for the Format Command continued…

Options for the Format Command

Using Windows Explorer to Manage Floppy Disks

Exchanging and Supporting Floppy Drives How to replace the drive How to add an additional floppy drive to a computer system Problems that can occur with a floppy drive and its support system

Replacing a Floppy Drive 1.Check that computer and other peripherals are working 2.Turn off computer and remove cover (Figure 6-20) 3.Unplug data cable and power cable from old drive; unscrew and dismount drive (Figure 6-21) 4.Slide new drive into bay; reconnect data cable and power cable (Figure 6-22) 5.Turn computer on; check setup; test drive

Replacing a Floppy Drive

Requirements for Adding a New Drive Empty bay Extra power cable (or “Y” splitter) Extra connection on floppy drive data cable

When a Floppy Disk Drive Doesn’t Work Check physical condition of disk Check error messages  Error messages in 600 range occur when a floppy drive does not pass POST test Check CMOS settings Check cables connected to drive

Common Error Messages Non-system disk or disk error. Replace and strike any key when ready. No operating system found. Bad or missing COMMAND.COM Error in Config.sys line xx Himem.sys not loaded Missing or corrupt Himem.sys Incorrect DOS version continued…

Common Error Messages Invalid Drive Specification Not ready reading drive A:, Abort, Retry, Fail? General failure reading drive A:, Abort, Retry, Fail? Track 0 bad, disk not usable Write-protect error writing drive A:

Chapter Summary Memory  Required for a system to work  Stored on microchips,which are often stored on memory modules (SIIMMs, DIMMs, or RIMMs)  Adding more memory can drastically improve performance Floppy drives  Once considered essential, now mainly used for troubleshooting a failed boot