Brian said:
Hi. I am looking at different RAMS to upgrade and pput in my pc.
On crucial.com it said I can use: "Each memory slot can hold DDR2
PC2-8500,DDR2 PC2-6400,DDR2 PC2-5300 with a maximum of 1GB per slot".
Some RAM I'v looked at uses MHz. Eg: Buffalo 2GB DDR2 667MHz 240-Pin
Computer Memory.
So, my question is: Can I use the MHz 240-Pin RAM's, or is this a different
kind of chip? Ot has the DDR2 and 240-PinI would assume they are the same but
how do I understand the DDR2 PC2-8500, 6400 or 5300 numbers in MHz. Is there
a conversion?
What is the difference in this situation between 8500, 6400 and 5300? I
would assume speed or something. I have looked in some stores and most said
5300 and other numbers on the tags, or I found the MHz numbers. I have yet to
find any 8500 or 6400.
Most people have said a 2GB piece would/may work in the slots if I tried.
But I just want to confirm it can. I would trust what Crucial.com says as
that site has been highly recommended on this forum to me often.
There is a nice table here, relating MHz to Bandwidth.
http://en.wikipedia.org/wiki/DDR2_SDRAM
DDR2-1066 means the bus is transferring data 1066 million times per second.
Since the DIMM is 8 bytes wide, the bandwidth is 1066*8 = 8500MB/sec, so they
call that PC2-8500. There is a fixed relation between the numbers, and
the numbers can be used interchangeably in certain situations.
A PC2-8500 stick, can operate at DDR2-1066, DDR2-800, DDR2-667, DDR2-533
and probably even DDR2-400. There is eventually a lower limit to the
operating speed, but you likely won't find it while playing with the
computer. That means the PC2-8500 stick is a "universal donor" in a
sense. Faster memory can be used with slower systems is a general
rule of thumb, which is why Crucial has named a number of different
options for you.
Based on your previous question, you're likely asking about your
Acer E380 with Geforce 6100 based motherboard.
http://www.crucial.com/store/listparts.aspx?model=Aspire E380
A near-equivalent, might be this Asus M2N-MX motherboard.
http://dlcdnet.asus.com/pub/ASUS/mb/socketAM2/M2N-MX/e3548_M2N-MX.zip
The QVL for that board, shows them using DDR2-533, DDR2-667, DDR2-800.
So it is possible you could benefit from RAM at PC2-6400 or PC2-8500,
with the PC2-8500 stick running at PC2-6400 when the BIOS sets it up.
Tbe stock BIOS would likely choose DDR2-800 as the fastest operating
choice. The processor has the memory interface, so the details are
not related to limitations of the chipset, but to the processor type.
(In other words, if you wanted to understand the limits, the
documentation would be on the AMD.com site, if you could find
it there.)
ftp://ftp.asus.com/pub/asus/mb/socketAM2/M2N-MX/M2N-MX_QVL.zip
If you're mixing your old memory with new memory, then the BIOS
picks the slowest conditions to make all the RAM work. If you
had DDR2-667 in the machine already, and installed something
capable of running DDR2-800 (such as PC2-6400 or PC2-8500), the
BIOS would still choose DDR2-667. If you then unplug the DDR2-667
memory, the BIOS should then change to DDR2-800. To verify the
behavior, given that the Acer BIOS is likely brain-dead and
not doesn't have good BIOS screens, you can use CPUZ to display
the current operating conditions. This is one way to learn about
how your machine is currently running.
http://www.cpuid.com/cpuz.php
*******
You may notice in the Crucial list, these two memories.
DDR2 PC2-8500 • CL=7
DDR2 PC2-8500 • 5-5-5-15
The first number on the "5-5-5-15" thing is CAS latency in clock ticks.
The "CL=7" means CAS latency is 7 clock ticks. Notice that the
CAS 7 kit is $62 and the CAS 5 kit is $93.
That means lower CAS is better. CAS is the delay from when you
request the data, until read data shows up on the bus. But again,
there is no point buying "muscle car memory" if you're mixing it
with your existing memory. Both the memory bus speed (DDR2-800)
and CAS (CAS 7) are adjusted for the slowest of all the memories
plugged in. If the old memory was DDR2-667 and CAS 7, then a CAS 5
stick would end up operating at CAS 7 like its partners. The memories
tend to share the same settings, because that makes the memory
controller design easier.
*******
Another thing to consider when buying memory, is the clearance between
the slots, and whether the modules have heat spreaders or not. Some
of the Crucial sticks have no heat spreaders on them, and have raw
memory chips.
All memory chips dissipate the same amount of heat, so "spreading"
the heat isn't absolutely necessary (not like RDRAM, where you could
have hot spots). But the metal plate still serves as a heat sink
(effectiveness proportional to surface area).
Now, on the one hand, you might think the heat spreader is doing you
a favor. If you have two sticks next to one another in the computer,
there is good air flow over one surface of each stick. If you sandwich
four sticks in close proximity, all with heat spreaders, then the middle
sticks get no good airflow. If the sticks had no heat spreaders, and
you had four of them, there is a tiny air channel between each stick.
That tiny air channel is likely only of value in a forced air scenario,
where there is "spill air" coming off the CPU fan, to help cool the
memory. The cooling might actually be better on a four stick config,
if there weren't any heat spreaders. It is kind of a toss-up, as to
which is the better investment.
All I can tell you, is the last four sticks of DDR2 I bought, had no
spreaders. Spreaders generally go with the "muscle car memory", so
they're practically unavoidable if you select a premium memory with
either a high DDR2-xxxx number or a memory with a low CAS latency.
When an enthusiast buys a premium memory, they likely run them
at elevated voltage, and the operating temperature soars. But an
enthusiast would likely only populate two of the memory slots, as
that helps allow higher overclocks on the memory. So in that situation,
a heat spreader is ideal. Some people operate their memory in such
extreme conditions, that they install a fan above the memory array.
There are even companies that make memory cooler systems for such
enthusiasts.
But on an Acer, running at stock speeds and using 1.8V for the DIMMs,
I don't see a strong need for spreaders.
Paul
