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Memory ratings and processors

 
 
Mark Scott
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      Apr 6th, 04, 12:36 PM
Does anyone have a list of what processors / bus speeds pair up with what
memory rating? IE 2700, 3200, 3500 etc etc?

Cheers

Mark


 
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Alex
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      Apr 6th, 04, 1:08 PM
"Mark Scott" <m@rk-> wrote in message
news:6Dwcc.3987$...
> Does anyone have a list of what processors / bus speeds pair up with
> what memory rating? IE 2700, 3200, 3500 etc etc?


DDR SDRAM PCnnnn numbers are an approximation of the peak transfer rate in
MB/s, which depends on the memory bus clock speed and width. The width is
always 64 bits (8 bytes), and two transfers (16 bytes total) can be made per
clock cycle. Therefore there is an (approx) factor of 16 between the ratings
and clock speed in MHz:

133MHz (effectively 266MHz) <-> PC2100
166MHz (effectively 333MHz) <-> PC2700
200MHz (effectively 400MHz) <-> PC3200

For AMD systems, it's usually best to match the memory bus speed to the FSB
speed, typically either 166MHz or 200MHz for current CPUs.

Pentium 4s are monumentally bandwidth hungry, and often perform best with as
much bandwidth as you can give them. The ideal situation is an 800MHz FSB
with dual-channel PC3200.

Alex


 
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Mark Scott
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      Apr 6th, 04, 1:32 PM
Thanks Alex

"Alex" <> wrote in message
news:c4u6jj$2l9dn3$...
> "Mark Scott" <m@rk-> wrote in message
> news:6Dwcc.3987$...
> > Does anyone have a list of what processors / bus speeds pair up with
> > what memory rating? IE 2700, 3200, 3500 etc etc?

>
> DDR SDRAM PCnnnn numbers are an approximation of the peak transfer rate in
> MB/s, which depends on the memory bus clock speed and width. The width is
> always 64 bits (8 bytes), and two transfers (16 bytes total) can be made

per
> clock cycle. Therefore there is an (approx) factor of 16 between the

ratings
> and clock speed in MHz:
>
> 133MHz (effectively 266MHz) <-> PC2100
> 166MHz (effectively 333MHz) <-> PC2700
> 200MHz (effectively 400MHz) <-> PC3200
>
> For AMD systems, it's usually best to match the memory bus speed to the

FSB
> speed, typically either 166MHz or 200MHz for current CPUs.
>
> Pentium 4s are monumentally bandwidth hungry, and often perform best with

as
> much bandwidth as you can give them. The ideal situation is an 800MHz FSB
> with dual-channel PC3200.
>
> Alex
>
>



 
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GSV Three Minds in a Can
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      Apr 6th, 04, 2:14 PM
Bitstring <6Dwcc.3987$>, from the
wonderful person Mark Scott <m@rk-sc0tt.?.c0.uk.invalid> said
>Does anyone have a list of what processors / bus speeds pair up with what
>memory rating? IE 2700, 3200, 3500 etc etc?


Alex gave you the right answer - just to add that PC3500 (and higher)
are not really official JEDEC specs, afaik, and are only useful if you
plan to overclock your FSB above 200 (aka 400 in AMDspeak, aka 800 in
Intelspeak) MHz. They also tend to be significantly more expensive.

To get the right answer for any particular PC or motherboard, try
www.crucial.com/uk/webpromo (the /webpromo is optional, but if you are
actually buying it's good for an extra 5% off, last time I looked).

--
GSV Three Minds in a Can
Outgoing Msgs are Turing Tested,and indistinguishable from human typing.
 
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Tim Auton
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      Apr 6th, 04, 4:28 PM
"Alex" <> wrote:
[snip]
>Pentium 4s are monumentally bandwidth hungry, and often perform best with as
>much bandwidth as you can give them. The ideal situation is an 800MHz FSB
>with dual-channel PC3200.


Ideally of course you'd want dual-channel, but assuming you've only
got the one: Is a 533 P4 better off with a single stick of PC2100
(matched bus speeds) or a single stick of PC3200 (max. bandwidth, but
out of synch)? Anybody got any benchmarks?


Tim
--
Love is a travelator.
 
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Alex
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      Apr 6th, 04, 5:06 PM
"Tim Auton" <tim.auton@uton.[groupSexWithoutTheY]> wrote in message
news:...
> Ideally of course you'd want dual-channel, but assuming you've only
> got the one: Is a 533 P4 better off with a single stick of PC2100
> (matched bus speeds) or a single stick of PC3200 (max. bandwidth,
> but out of synch)?


I strongly suspect the latter. The difference between PC2100 and PC3200 is
substantial, and the FSB is significantly faster than either (which makes
running asynchronously less important).

> Anybody got any benchmarks?


I'm sure there will be some to be found on the web, but I don't have time to
look right now...

Alex


 
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