PC Repair II Notes and Lab on Memory
I. Types of Memory
system has RAM, and Cache memory on the motherboard and CPU.
RAM is stored on the motherboard. L1
and L2 are cache memory, stored on the the Motherboard or on the
Processor. Cache memory is much faster, but more expensive than normal
RAM. Adding cache memory speeds up
the PC, but makes it more expensive. Some processors are limited in RAM by the
amount of RAM that can be cached. For
example if your processor can only cache 128 Megs of RAM, expanding to 256 Megs
may actually slow down your PC! Make
sure you know if your PC can cache the extra RAM you want to add before even
considering adding it! Most current
processors have 128K to 512K cache, the more the better!
II. Memory Handling in Win 9X
9X accesses the protected mode of the x86 processors and as such can access much
more than the 1 Meg allowed in DOS. This
memory is divided into parts in Windows. Windows can also page or swap memory from RAM to the Hard
Drive to make it appear to have even more memory than the actual RAM.
Since the Hard Drive is much slower than RAM, when this occurs there is
degradation in speed. This memory is called the SWAP File.
is the total memory available to Windows: base, extended, virtual (swap file).
Virtual memory is "fake memory," where a portion of the hard disk is used as overflow memory.
95 creates a temporary swap file (WIN386.SWP) that changes
according to need. This is an
option that can be overturned. You
can allocate a fixed size and location of swap memory for windows.
To adjust the Windows 95 swap file, double-click the System
icon in the Control Panel and select the Performance tab followed by Virtual
it is lesser known, GDI Heap is memory that is used to store the
graphical elements of Windows, such as icons and bitmapped images. If you run
programs that use many bitmaps, icons, and so on, you might run out of GDI Heap.
User Heap is memory that is used to hold information about active
windows and other related information. In Windows 3.x, the Menu and String Heaps
are included in the User Heap. This heap is also only 64K.
can also obtain DOS memory information from within Windows 95.
30 PIN vs 72 Pin Vs 168 PIN
(Single Inline Pins), SIMMS (Single Inline Memory Module), DIMMS (Dual Inline
Memory Module 168 PIN, 64 BIT, normally SDRAM now).
computers rely on DIMMS while older machines rely on SIMMs and sometimes SIPs
for extra memory. If you have a vacant memory bank, you can install this type of
extra memory. SIMM, DIMM, and SIP memory are similar; several memory chips are
bundled into one package. Unlike DIP memory, SIMM/DIMM/SIP memory enables you to
install the equivalent of nine chips in one motion, rather than one at a time.
you need to get the right memory. For
this you need to look in the book which came with the computer and find out what
type, and speed and capacity your PC will take. Then purchase the memory from a computer parts store, the
internet, or a place like Office Depot. Make
sure you have the empty space to put the chips, or you may need to take out the
existing chips and replace them with larger capacity ones!
your PC, make sure everything is working correctly, and record the current
amount of memory. _______________
(you can tell this in windows 9X by right clicking my computer and left clicking
properties). If you have diagnostic
software see if you can tell how much Cache Memory is present.
windows and if necessary turn off the
computer and remove its case.
yourself by touching the case on direct metal, then uplug the PC.
the banks of memory chips and the vacant memory bank.
usually see two memory banks that hold four SIMMs or SIPs each. Pentium
computers use two banks of two SIMMs. The newer 168-pin DIMM style of memory has
up to 4 banks of one DIMM each. DIMM banks can be in addition to two 72-pin SIMM
the numbers on the SIMM/DIMM/SIP memory chips in the full memory bank and order
additional memory for the vacant bank.The chips in the other memory bank are
probably the type of memory chips you need to order. The current SIMM/SIP chips
probably have these numbers within the chip's part number, which is printed on
the top of the chip.
256K x 1 bit
you have a vacant memory bank, you probably want to add chips that match the
current ones. For accuracy, consult the owner's manual about the type of chips
to add. If you don't have an owner's manual, consult the previous table of
possible memory configurations for SIMM/SIP chips. Remember that if you add
extra memory to the computer, its speed must be equal to or less than that of
the memory that is already installed.
the SIMM/DIMM/SIP memory into the sockets.
SIMM/DIMM/SIP must be installed pointing in a certain direction. Each chip has a
polarity notch on one end of the circuit board. A SIMM has a notch cut into one
side and mounting holes into which metal clips fasten. A SIP has a diagonal
notch. A DIMM, meanwhile, relies on two notched keys in the socket that prevent
it from being installed incorrectly. If the module is reluctant to enter its
socket, try turning it around.
each SIMM/SIP at about a 45-degree angle, lining up the copper-colored
connectors on the memory module with the socket on the motherboard. The chips on
the module face away from the angle of the socket. Because four modules must be
installed into the bank, you must insert the modules in a certain order so that
each subsequent module has room to be inserted at this angle.
insert the SIMM into the socket. Next, pivot the SIMM backward to an upright
position until it touches the plastic latches on both sides of the socket.
Carefully press the SIMM against these latches until they snap around the edges
of the SIMM, and then clamp it firmly into place. The circuit board that serves
as the backbone of the SIMM needs to be perpendicular to the circuit board that
holds the socket.
or metal finger from the socket latch should poke slightly through the alignment
hole at the edge of the SIMM (if the SIMM has holes), or the side latches of the
socket should wrap around the board of the SIMM. For each SIP, insert the module
straight into the SIP socket. You should feel the SIP slide into the grasp of
the socket's contact fingers.
168-pin DIMMs, insert the module straight down into the socket until the clips
hold it in place.
the case, and restart the PC
the BIOS recognizes the new memory. It may be necessary to save the BIOS with
the new settings, if you have changed the amount of memory in the PC.
OS and determine how much memory you have now.________________