DDR Memory Information:
DDR
Memory modules 101: The basicsPart Number
This is the unique identifier that Crucial assigns to
every memory module.
Module
Size
The total number of bytes (usually expressed in megabytes
or MB) on the memory module.
Package
The number of pins (30, 72, 100, 144, 168, 200) and the
type of memory module (SIMM, SODIMM, DIMM, RIMM) for this
part number.
Feature
The type of DRAM on this memory module. Current DRAM types
includes FPM, EDO, SDRAM, DDR, and RDRAM.
Configuration
This describes the structure of the memory module. The
first number is the depth of the module (or, the number
of signals the module sends at one time). The second is
the width (of the module's data bus). To get the total
megabytes of the module, multiply the depth by the width
and divide by 8 (or 9 for ECC or parity; if you're not
sure if you have ECC/Parity divide the width by which
ever one gives you an integer). For example, a 16M72 is
16 x 72 / 9 = 128MB.
DIMM Type
This refers to how the DIMM processes signals. There are
three DIMM types: buffered, registered, and unbuffered.
Most memory modules are unbuffered.
Buffered modules
contain a buffer (usually when there's a lot of memory)
to help the chip set cope with the large electrical load
required. The buffer electrically isolates the memory
from the controller to minimize the load that the chipset
sees.
Registered
modules contain a register that delays all information
transferred to the module by one clock cycle. Again, this
is usually done on modules with a lot of memory to help
ensure that the data is properly handled.
Most buffered
and registered modules also have ECC and are used in servers.
FPM and EDO modules are either unbuffered or buffered.
SDRAM modules are either unbuffered or registered.
Error Checking
There are two different types of error checking: parity
and ECC (Error Checking and Correction) Parity modules
have an extra chip that detects if data was correctly
read or written by the memory module, depending on the
type of error. However, it will not correct the error.
ECC modules have an extra chip that detects if the data
was correctly read or written by the memory module. If
the data wasn't properly written, the extra chip will
correct it in many cases (depending on what type of error).
Non-ECC (also called non-parity) modules do not have this
error-detecting feature.
EDO and FPM
modules utilize either parity or ECC. SDRAM, DDR, and
RDRAM modules utilize ECC. All types of memory can also
be non-parity.
Component
Speed
This is how fast the components on your memory module
are capable of running. Speed is expressed in nanoseconds
(lower is faster). Keep in mind, with SDRAM, the memory
module will only run as fast as the speed of your processor's
front side bus.
Voltage
This refers to the amount of power the memory module needs
to function. The module gets its power from your system's
power supply, which is why designers are always trying
to reduce memory voltage requirements. FPM and some EDO
parts run at 5 volts, some EDO and all SDRAM parts run
at 3.3 volts, and DDR runs at 2.5 volts.
SDRAM Timings
This refers to the latency of the parts, or the amount
of time it takes for the memory to respond to a command.
Latency is measured in terms of clock cycles and is often
noted as CL2 (two clock cycles) or CL3 (three clock cycles).
For most applications there is very little difference
in performance between CL2 and CL3 parts.
--The above
information courtesy of Crucial.com
More DDR
Information:
"Crucial
PC1600 / PC2100 DDR Memory Review"
--------------------------------------------------------------------------------
In the last
few months, the PC industry has been witness to some very
exciting developments. Processors that were once considered
fast (350-500MHz), have been supplanted by small squares
of silicon which can easily run well over the 'magical'
threshold of 1.0GHz. Still newer processors are on the
drawing boards of chip designers which by the end of this
year are expected to break the 2.0GHz+ barrier!
Along the way, there has been a push in the SDRAM manufacturing
industry to have the present type of memory run faster,
alongside the blazing processor speeds now available in
the PC marketplace. The current iteration of SDRAM has
begun to show its' limitations in memory bandwidth with
both PC100/PC133 SDRAM platforms. By causing a bottleneck
in the performance of these new processor speed demons,
memory is starting to be the limiting factor to the question,
"how fast can you go?"
DDRAM (Double
Data Ram) evolved from the need to search out an alternative
to SDRAM to free up this pressing bandwidth limitation.
Behind
DDR
First, a little
background on how AMD and Intel ended up in their current
market positions, and the influence this has had on the
current state of RAM support.
DDR memory has 184 pins, where as SDRAM has 168.
The reason behind this sudden shift in the PC market towards
the Athlon and Duron can be attributed to AMD's lower
costs when compared to its primary competitor, Intel.
The Pentium
III processor which Intel had on the market at the time
of this shift in market share did not appear as leading-edge
as the Athlon or the Duron. In recent reviews on the web,
as well as in the traditional printed medium, the Intel
Pentium III and the Celeron processors were found to be
slower in certain benchmarks (when compared alongside
the same MHz clocked AMD Athlon and its lesser priced
Duron).
With these
encouraging reviews and strong performance showings, along
with the quick acceptance towards its cpu's from the buying
public in a matter of months, AMD was able to gain a very
strong following with its processors. This shift was attributed
primarily to its aggressively priced products and its
very strong performance.
Another reason
for Intel's slip in the PC market can be attributed to
its own insistence in pushing the technology envelope
unto its consumers. This happened whether the customer
was willing to accept the latest advancements or not.
Mainly this revolved around a deal Intel had signed with
Rambus Ram so that would develop its chipsets and processors
to work alongside Rambus Ram technology exclusively.
This new partnership
encountered a few major setbacks. First there was resistance
by the general buying public and small businesses due
to Rambus's extremely high memory costs. Another incident
which really hurt Intel's future share of the marketplace
was their i820 chipset.
This chipset
which was originally developed to support only RDRAM (Rambus
RAM), was found to have a bug in its design when matched
with an MTH (Memory Translation Hub), that allowed the
use of SDRAM, which would ultimately cause serious data
corruption or loss in certain circumstances.
This major
technological gaffe coincided with the sudden shortage
of higher-clocked CPU's such as the 1.0GHz which Intel
made available only to its select few major Tier-1 OEM
PC manufacturers (ie. Gateway, Dell, Compaq). This caused
a major public relations fiasco for the once solidly-designed
CPU/chipset technology firm.
AMD stepped
in at the right time with a large and steady supply of
its processors. The PC market was ready for faster CPU's
and AMD was more than able to produce them in high yields.
AMD was able to provide faster clocked processors to the
buying public much quicker than its competitor, Intel.
Intel did not have, nor could it produce Pentium III's
in large quantities at the time. This allowed AMD to continue
grabbing a larger share of the processor market that was
once owned exclusively by Intel.
Now that AMD
was considered a major competitor to Intel in the processor
market, VIA a Taiwanese chipset manufacturer developed
a much more stable chipset. The less expensive chipset
supported AMD cpu's and were able to offer features which
Intel's own aging BX chipsets weren't able to provide.
Intel's i820 couldn't survive long enough for the general
public to purchase or accept: PC100/ PC133 SDRAM; ATA
66/ ATA 100; 4x AGP support.
VIA soon replaced
their original AMD-only KX133 chipset, and improved upon
its design with their current KT133A chipset which supports
the newer Athlon's running at 200MHz or 266MHz FSB (Front
Side Bus).
As mentioned
earlier, AMD wanted to specify a new type of RAM which
would provide a higher memory bandwidth when compared
to the current bandwidth limited SDRAM platform - enter
DDRAM.
"Crucial
128mb PC2100 DDR SDRAM Review:"
Common PC100/133
SDRAM is, no doubt, at its peak. Prices have yet again
dropped to a nice low, and quality has risen (OCZ PC180
Cas3 comes to mind). However, as the years go by every
technological advancement starts to show its limits, and
what we are seeing here is perhaps the start of the limitations
for your common SDRAM. Double Data Rate (DDR) SDRAM has
hit the scene.
DDR SDRAM
works exactly how it sounds. The bandwidth of the RAM
is theoretically doubled, as the traffic of data flows
on both the rising and falling edges of the clock. This
method has proven to be more efficient than the rather
over priced RDRAM, which works with current P4 system
based on the i850e chipset, and some older P3/i820e systems.
However, many are not overly impressed with the current
performance gain DDR RAM brings over SDRAM, so purchasing
a whole new mainboard and memory module seems unnecessary.
Crucial
Technology -- The Memory Experts (TM)
As the subheading
suggests, Crucial know what their doing. My previous review
on the Crucial PC100 128MB stick left me impressed, being
very cheap and yet maintaining high quality performance.
in other words, Crucial are indeed experts in the area
of Memory. This module, priced at a very reasonable US
$31.49, seems to offer the same brilliant price/performance
ratio.
Crucial are
generally Internet based. They do roughly 90% of their
transactions over the Internet, which helps them cut down
on the costs of the 'middlemen' and generally helps them
bring you, the consumers, greater efficiency with customer
support and prices. As you may have noticed, this module
costs no more than Crucial PC133 128MB sticks, which is
extremely well priced.
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