System Memory
-Memory is widely discussed and can
determine better performance in the PC system. Now most of you know of RAM
this stands for (Random Access Memory). This memory is considered
volatile, which comes down to being erased when the computer is turned off thus
cutting power to the RAM. What are the types out there? There are two
basic forms which spur into more types of memory used for video cards,
motherboards and so on.
Basic Types and Operation
-Memory holds information that was
derived from the hard drive. Data is stored using bits and is interpreted
as a (0) or a (1). A (0) indicates a no voltage applied and a (1)
indicates a charge. Charge what you ask? Well on a SIMM or DIMM modules
(discussed in Formats) there are little black chips that contain millions
of tiny transistors. These are used to store your information temporarily.
Of course the information is refreshed often so to stay current. Not only
is this type memory important but your system uses cache memory on the
processor and on the motherboard for even faster access times. Take note
that the RAM is what is also called volatile memory. This means when you
turn that old computer off, all the information in those charged
transistors is gone. Now we have a zero charge and no information.
-Most common types of memory you will run
into is DRAM, and VRAM. The DRAM has different technologies attached to it
such EDO (Extended Data Out), FPM (Fast Page Mode), BEDO (Burst Extended
Data Out), and SDRAM (Synchronous Dynamic Random Access Memory). This
sounds pretty confusing doesn't it? Just remember DRAM and this memory has
technologies added to it. Example :
-EDO DRAM, this is a
little faster than the FPM and is used in newer machines of today that do
not exceed 75 Megahertz Bus speed.
-BEDO DRAM, This is EDO on
steroids that allows pipeline of information. This also allows faster bus
speeds and is a quick RAM. But the bad side is that it never really caught
on with motherboard chipset support.
-FPM DRAM, This is also
called Non-EDO RAM and is pretty universal with all systems that do now
exceed 66 MHz bus speed. This type memory basically allows pages of 7
kilobytes that can be loaded and subsequent request can be made without
delay making FPM fast.
-SDRAM, This type of RAM
uses the same Bursting technique like the BEDO RAM and also enjoys running
at the system clock speed of 100 MHz. Good Stuff !!
-The main stay of these today are SDRAM.
Most likely this will become the next standard till something else comes
along to wipe it out. Lets figure out what formats these type of memory
come on.
-So far we know that RAM comes in SIMM and
DIMM format. We know the types of RAM and now we know some more about
error correcting otherwise known as Parity. This comes down to security
for those who are worried about errors.
-RAM also over the years has had some neat
tricks added to it. If you have a RAM chip that is doing a ga-zillion
operations you might want to check it for error right? Naaa, but some do,
this is done by using parity RAM or ECC RAM. So not to throw you off it
would look something like this added to the rest of what you learned ECC
EDO-SDRAM. Meaning, Error Correcting Code- Extended Data Out -Synchronous
Dynamic Random Access Memory. Geezzz, get real huh!? Or just Parity
RAM. Well there is also non-parity RAM which just means it doesn't have
the extra chip to check for errors and is cheaper.
-This is how Parity RAM works for those
interested. Using extra chips on the RAM allows it to keep track of bits.
The ninth bit sent through would do a check sum to make sure all
the other 8 bits matched up. If something shows up wrong the system will
know it then. Now lets look at ECC Ram.
-ECC (error correcting Code),
checks for errors and even can fix the wrong bit to the right value
allowing the system to keep on trucking. ECC is probably the way to go but
is a little more expensive. Actually both types of memory is real
important if you run a server or applications that are real sensitive.
-Having a memory problem can
be really confusing. Don't let it get to you first off. One thing to
consider about memory is what the errors are when a chip goes bad. This
can be mistaken for another application or components going bad. There are
some typical symptoms to look at with memory trouble and some ideas of
solving which SIMM or DIMM is causing it. The good news in memory
is, if it is bad it usually occurs when you first get
the system. This means that it is under warranty and can be replaced or
shipped to manufacturer.
-For more information on
memory take a look at |Guides|.
-Symptoms Of Memory Failure-
-The part of all this that is
a real bummer is that the errors can pop up anywhere. You have to consider
how much system information is in memory. Another thing to consider is
memory error don't always occur till you make use of high memory areas. If
you are using a high end application that uses extreme amounts of memory
this may be a consideration.
-If you have parity memory
this can be of great help. When you get a parity error it will usually
give a memory address that you can pinpoint where the problem is. On
non-parity which many of us have the problem is wider.
Non-Parity Isolation
-Some of these steps should be
taken regardless if you use parity on non-parity memory.
-
Shut system down
-
Try and reseat memory
modules if they seem loose.
-
If this does not help
simply take one module out that you suspect.
-
Run system and see if
errors occur. If no error occurs the problem may be with the SIMM or
DIMM you took out. Try taking the other memory slot out and replacing
in the now open slot of the suspected bad SIMM. Boot up and see if you
run with no errors
-
If you did get an error
this may be with the slot and not the memory
-This is simply just a process
of elimination. If all fails, take memory back if under warranty and
replace. If your are still having trouble double check and make sure you
have the right memory. If that is okay maybe a new motherboard is
necessary.
Cache Memory
-Well system cache is much
like system memory. If you run into problems with it, it is hard to
diagnose. But the good news is that a software tweak can help. If you need
a better background on cache go to |Guides|.
-Troubleshoot-