Can I use a 400Mhz DDR ram memory on a 300mhz bus motherboard?

  • Thread starter Thread starter Admin
  • Start date Start date
Admin said:
Hi,

Can I use a 400Mhz ddr ram memory on a 300mhz bus motherboard?
I have an Asus A7S8X-MX motherboard
(http://www.asus.com/products/mb/socketa/a7s8x-mx/overview.htm) that
accepts 333Mhz Ram memory. I have a 400Mhz 1GB DDR Ram memory. Are they
both compatible?

--
Thanks,

Admin.
Want to buy me a book? http://tinyurl.com/78xzb :)
Click to expand...

The manual is
http://www.asus.com/pub/ASUS/mb/socka/sis741GX/e1766_a7s8x-mx.pdf

It says, as you say. RAM supported is 200/266/333

Meaning that the memory bus clock runs at a max speed of 333.

400MHz RAM just means that RAM is designed to be able to run as fast as
400MHz. So it is designed so it can run lower too. So you can put
'400MHz' RAM in there are run it at 333MHz(called underclocking - lower
than specified speed). But you can't run your 400MHz RAM at
400MHz(called stock speed - at specified speed), because your memory
bus's max speed is 333.


Now, as to Why RAM cannot internally run at a faster speed than the
memory bus. That I do not know. Given that the CPU can use a
multiplier to go faster than the FSB.
Here is a diagram showing FSB and memory bus
http://static.howstuffworks.com/gif/motherboard-busses.jpg

Also, it seesm - and i'm not usre about this - that later systems have
an independent memory bus., that can be incremented by increments as
small as 1Hz. Older systems have a memory bus that runs at a multiple
or ratio of the FSB clock. So I guess memory on that system is limted
by the fastest multuiplier in the system.


Either way. in your case, the fastest memory can run at is 333. You can
use '400Hz RAM' but only running as high as 333 MHz.
 
Admin said:
Hi,

Can I use a 400Mhz ddr ram memory on a 300mhz bus motherboard?
I have an Asus A7S8X-MX motherboard
(http://www.asus.com/products/mb/socketa/a7s8x-mx/overview.htm) that
accepts 333Mhz Ram memory. I have a 400Mhz 1GB DDR Ram memory. Are they
both compatible?
Click to expand...

Yes!

You are getting your terms mixed up though - DDR400 runs at 200MHz (and
DDR333 at 166.6MHz). DDR stands for double data rate, which means the memory
can do 2 transfers per clock tick. The DDR rating of the memory is its
maximum rated stable speed, so can be run slower.
 
GT said:
Yes!

You are getting your terms mixed up though - DDR400 runs at 200MHz (and
DDR333 at 166.6MHz). DDR stands for double data rate, which means the memory
can do 2 transfers per clock tick. The DDR rating of the memory is its
maximum rated stable speed, so can be run slower.
Click to expand...

Maybe It's *slightly* better to say DDR400 rather than DDR 400 MHz
But even Kingston say
"DDR 400 MHz"
http://www.ec.kingston.com/ecom/configurator/PartsInfo.asp?ktcpartno=KHX3200/1G
Anf it's still not perfectly clear, even saying DDR 400 (ommitting MHz
means effective speed! not actual speed. That is confusing too - to the
uninitiate).

Most of the speeds.
266, 333, 400, <-- you know these are the *2 speeds.
and
133, 166, <-- you know these are just bus speed.
PC66,PC100,PC133. <-- also single of course.

200MHz. That seems ambiguous, because - from googling - there is such
a thing as DDR200(100*2). And of course there is DDR400(200*2).
So tere is a bus of 200 and a bus of 100. So if they say 200, you
gotta know if they mean Actual speed(single bus) or Effective
speed(takening into account dual pumped).

Trouble's coming 'cos even 400MHz, is ambiguous now. DDR800 is out, and
of course, it's 400MHz*2.


MAybe those other terms are less ambiguous. Like PC1600 and PC3200
PC1600 (DDR200(100*2))
PC3200 (DDR400(200*2))

useful article
http://www.quepublishing.com/articles/article.asp?p=339089

166.66 MHz * 2 transfers per cycle * 8 Bytes = 2666 MB/sec = PC2700

16* actual. actual*2*8

But still. they are large numbers.


CONCLUSION
Best to say DDR 333=166*2, 800=400*2, 400=200*2, e.t.c.
Then there's no ambiguity. And it fights off the garbage marketting.
We shouldn't let marketting vocabuary get so invasive, that even RAM
manufacturers get poisoned by it.
 
Maybe It's *slightly* better to say DDR400 rather than DDR 400 MHz
But even Kingston say
"DDR 400 MHz"
Click to expand...

It's not just slightly better, it's technically correct and
necessary to avoid confusion. True, there are plenty of
people that use the wrong term, hence the inconsistencies
and puzzlement of some users. That's why we have standards
to make things clearer. Web authors, even Kingstons, are
not necessarily technically minded. Sad but true... I know
a few webmasters that couldn't tell you much of anything
about hardware that can't be gleaned from reading a CompUSA
advertisement.

http://www.ec.kingston.com/ecom/configurator/PartsInfo.asp?ktcpartno=KHX3200/1G
Anf it's still not perfectly clear, even saying DDR 400 (ommitting MHz
means effective speed! not actual speed. That is confusing too - to the
uninitiate).

Most of the speeds.
266, 333, 400, <-- you know these are the *2 speeds.
and
133, 166, <-- you know these are just bus speed.
PC66,PC100,PC133. <-- also single of course.

200MHz. That seems ambiguous, because - from googling - there is such
a thing as DDR200(100*2). And of course there is DDR400(200*2).
So tere is a bus of 200 and a bus of 100. So if they say 200, you
gotta know if they mean Actual speed(single bus) or Effective
speed(takening into account dual pumped).
Click to expand...

You just need to know the clock frequency and data rate.
200MHz should never be used as the data rate, always the
clock frequency. DDR200 or QDR200 (except QDR200 doesn't
exist, slowest QDR rate is QDR400). QDR is a less common
term, since everyone just calls it "quad pumped" instead.
Thank intel for dumbing-down technical terms so the masses
would think their products are so much faster. Creative
marketing can be a bad thing for those who have to deal with
the target market.

That is why the terms for data rate such as DDR exist in the
first place, so people wouldn't go around using "MHz" for
both.
 
Now, as to Why RAM cannot internally run at a faster speed than the
memory bus. That I do not know. Given that the CPU can use a
multiplier to go faster than the FSB.
Click to expand...

There is absolutely no reason why RAM cannot run internally faster than the
memory bus but also absolutely no reason to do it. With a CPU it has to
crunch data so running faster internally than the data arrives is a good
thing. RAM, however, is just storage space, it does no processing. Why would
you need it to store data faster than it is getting it? It makes no sense
and would serve no purpose.
 
~misfit~ said:
There is absolutely no reason why RAM cannot run internally faster than the
memory bus but also absolutely no reason to do it. With a CPU it has to
crunch data so running faster internally than the data arrives is a good
thing. RAM, however, is just storage space, it does no processing. Why would
you need it to store data faster than it is getting it? It makes no sense
and would serve no purpose.
Click to expand...

I see. it would serve no purpose. But still i've never seen any option
to do it. Is there even a multiplier there for it?
 
I see. it would serve no purpose. But still i've never seen any option
to do it. Is there even a multiplier there for it?
Click to expand...

Not only would it serve no purpose, it would require a
buffer and that additional latency... it would be slower and
more expensive. Why have an option to do something with no
purpose?
 
I see. it would serve no purpose. But still i've never seen any
option to do it. Is there even a multiplier there for it?
Click to expand...

Why would anybody provide a feature that serves no purpose other than to
further (pointlessly) stress the RAM? No, there isn't a multiplier for it.
Never has been, never will be. The RAM runs at the speed of the bus it's on.
Period.

The only thing that comes close to a RAM multiplier is DDR and QDR ("Quad
Pumped" to use Intel's terminology) RAM. This RAM is supposed to
accept/deliver data at either twice or four times the clock speed of the
bus. However it doesn't run at 2 X or 4 X the speed no matter how often
manufacturers or marketers talk about "400MHz RAM" or "800MHz FSB". Those
are lies. However getting the companies involved (Intel et al) to stop
telling lies would be high on impossible.
 
Back
Top