Matching FSB and Memory Speeds

I'm not much of a hardware person, so sorry if this sounds a little silly.

I'm researching which Dell desktop to buy and what features my computer should have. I've read that one way to get the most performance from a PC is to match the data transfer rates of the RAM and the CPU's front side bus. Even learned the formula to calculate data transfer rates:

cycles/second x data transfers/cycle x bytes/transfer = MB/sec data transfer rate (doubled for dual channel memory)

The thing is, I can't seem to come up with a combination of a Core 2 Duo processor and RAM that have the same data transfer rate. At least, not for the CPUs and RAM offered on Dell's Home and Home Office desktops.

Am I doing something wrong?

Is it still true that you're supposed match data transfer rates?

Appreciate your advice.

Daddy

"Daddy" <> wrote in message
news:X-...
I'm not much of a hardware person, so sorry if this sounds a little silly.

I'm researching which Dell desktop to buy and what features my computer
should have. I've read that one way to get the most performance from a PC is
to match the data transfer rates of the RAM and the CPU's front side bus.
Even learned the formula to calculate data transfer rates:

cycles/second x data transfers/cycle x bytes/transfer = MB/sec data transfer
rate (doubled for dual channel memory)

The thing is, I can't seem to come up with a combination of a Core 2 Duo
processor and RAM that have the same data transfer rate. At least, not for
the CPUs and RAM offered on Dell's Home and Home Office desktops.

Am I doing something wrong?

Is it still true that you're supposed match data transfer rates?

Appreciate your advice.

Daddy


------------------------------------------------------------



Example:

1600mhz(CPU external clock)= (max RAM speeds of) 800mhz x 2 ( or
'double-pumped') max FSB speeds

1333mhz (CPU external clock) =(max RAM speeds of)667mhz x 2 ( or
'double-pumped') max FSB speeds

1066mhz (CPU external clock) = (max RAM speeds of) 533mhz x 2 ( " "
" ) max FSB speeds


^^^ CPU external clock will dictate maximum FSB speed. (i.e.- 800mhz DDR2
will 'throttle back/slow' to speed dictated by, say, a CPU with an external
clock speed of LESS than 1600mhz and run at those slower speeds.)


No real use in buying RAM of a faster speed than the CPU FSB/external clock
speed.

hth

Thank you for that. I don't know why I didn't see it earlier (too much Tom's Hardware Guide).

A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum throughput of 10,664 MB/sec. (on paper at least), which is a good match for 667 MHz DDR2-SDRAM (= 333 MHz double-pumped) that has a maximum throughput of 10,672 MB/sec in dual channel.

Let me give a specific example: One computer I'm looking at is the Inspiron 530 desktop. The Core 2 Duo E6550 offers the fastest FSB available for this Inspiron, at 1333 MHz, which can achieve a maximum throughput of 10,664 MB/sec (as above). Why then would Dell offer 800 MHz DDR2 dual channel RAM - with a maximum throughput of 12,800 MB/sec - for this computer? What's the point - bragging rights? That's the part I don't get.

Daddy

"S.Lewis" <> wrote in message news:cwVjj.54670$. ..
>
> "Daddy" <> wrote in message
> news:X-...
> I'm not much of a hardware person, so sorry if this sounds a little silly.
>
> I'm researching which Dell desktop to buy and what features my computer
> should have. I've read that one way to get the most performance from a PC is
> to match the data transfer rates of the RAM and the CPU's front side bus.
> Even learned the formula to calculate data transfer rates:
>
> cycles/second x data transfers/cycle x bytes/transfer = MB/sec data transfer
> rate (doubled for dual channel memory)
>
> The thing is, I can't seem to come up with a combination of a Core 2 Duo
> processor and RAM that have the same data transfer rate. At least, not for
> the CPUs and RAM offered on Dell's Home and Home Office desktops.
>
> Am I doing something wrong?
>
> Is it still true that you're supposed match data transfer rates?
>
> Appreciate your advice.
>
> Daddy
>
>
> ------------------------------------------------------------
>
>
>
> Example:
>
> 1600mhz(CPU external clock)= (max RAM speeds of) 800mhz x 2 ( or
> 'double-pumped') max FSB speeds
>
> 1333mhz (CPU external clock) =(max RAM speeds of)667mhz x 2 ( or
> 'double-pumped') max FSB speeds
>
> 1066mhz (CPU external clock) = (max RAM speeds of) 533mhz x 2 ( " "
> " ) max FSB speeds
>
>
> ^^^ CPU external clock will dictate maximum FSB speed. (i.e.- 800mhz DDR2
> will 'throttle back/slow' to speed dictated by, say, a CPU with an external
> clock speed of LESS than 1600mhz and run at those slower speeds.)
>
>
> No real use in buying RAM of a faster speed than the CPU FSB/external clock
> speed.
>
> hth
>
>
>
>
>
>
>

"Daddy" <> wrote in message
news:. ..
Thank you for that. I don't know why I didn't see it earlier (too much Tom's
Hardware Guide).

A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum
throughput of 10,664 MB/sec. (on paper at least), which is a good match for
667 MHz DDR2-SDRAM (= 333 MHz double-pumped) that has a maximum throughput
of 10,672 MB/sec in dual channel.

Let me give a specific example: One computer I'm looking at is the Inspiron
530 desktop. The Core 2 Duo E6550 offers the fastest FSB available for this
Inspiron, at 1333 MHz, which can achieve a maximum throughput of 10,664
MB/sec (as above). Why then would Dell offer 800 MHz DDR2 dual channel RAM -
with a maximum throughput of 12,800 MB/sec - for this computer? What's the
point - bragging rights? That's the part I don't get.

People erroneously expect a faster memory part to operate faster in all
cases. You're right, the 800 MHz DDR2 will actually be slower in your
example. Sometimes, though, the faster memory can be cheaper than older,
slower, scarcer parts and manufacturers use them for that reason also.

Tom Lake

Reply bottom posted, as appears to be the custom.


"Tom Lake" <> wrote in message news:fmq87v$kgm$...
>
> "Daddy" <> wrote in message
> news:. ..
> Thank you for that. I don't know why I didn't see it earlier (too much Tom's
> Hardware Guide).
>
> A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum
> throughput of 10,664 MB/sec. (on paper at least), which is a good match for
> 667 MHz DDR2-SDRAM (= 333 MHz double-pumped) that has a maximum throughput
> of 10,672 MB/sec in dual channel.
>
> Let me give a specific example: One computer I'm looking at is the Inspiron
> 530 desktop. The Core 2 Duo E6550 offers the fastest FSB available for this
> Inspiron, at 1333 MHz, which can achieve a maximum throughput of 10,664
> MB/sec (as above). Why then would Dell offer 800 MHz DDR2 dual channel RAM -
> with a maximum throughput of 12,800 MB/sec - for this computer? What's the
> point - bragging rights? That's the part I don't get.
>
> People erroneously expect a faster memory part to operate faster in all
> cases. You're right, the 800 MHz DDR2 will actually be slower in your
> example. Sometimes, though, the faster memory can be cheaper than older,
> slower, scarcer parts and manufacturers use them for that reason also.
>
> Tom Lake
>
>
Thanks to both of you for your help.

"Sometimes, though, the faster memory can be cheaper than older,
slower, scarcer parts and manufacturers use them for that reason also."

Similarly, when I upgraded the memory in my gracefully aging Dimension 4500 I had to buy faster memory since the original speed was scarce.

Thanks again. A good group, this. A little "wild, wild west" compared to the Dell Community Forums, but a different (and often refreshing) perspective.

Daddy

"Daddy" <> wrote in message
news:. ..
Thank you for that. I don't know why I didn't see it earlier (too much Tom's
Hardware Guide).

A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum
throughput of 10,664 MB/sec. (on paper at least), which is a good match for
667 MHz DDR2-SDRAM (= 333 MHz double-pumped) that has a maximum throughput
of 10,672 MB/sec in dual channel.

Let me give a specific example: One computer I'm looking at is the Inspiron
530 desktop. The Core 2 Duo E6550 offers the fastest FSB available for this
Inspiron, at 1333 MHz, which can achieve a maximum throughput of 10,664
MB/sec (as above). Why then would Dell offer 800 MHz DDR2 dual channel RAM -
with a maximum throughput of 12,800 MB/sec - for this computer? What's the
point - bragging rights? That's the part I don't get.

Daddy


The answer is really simple: supply and demand as well as costs.

As quickly as speeds improve and move upward, it's entirely possible that
Dell can purchase (at a given time) the 800mhz as cheaply as the 667mhz DDR2
RAM.

In the past, an example of this would be, say, a Pentium 4 /2.4GHz/400mhz
FSB CPU system that could only utilize RAM speeds of up to 266mhz (PC2100),
but was built and shipped with 333mhz (PC2700) DDR.

Why? Because as speeds and production of the RAM continually move upward and
forward, the 333mhz was likely more plentiful and perhaps even cheaper -
even though it will only run at the 266mhz rate in the example machine. They
usually did this at no extra charge.

Now in your example, if you're facing an optional UPcharge for the 800mhz
RAM, it would be pointless to pay more for the 800mhz option since the CPU
is operating at 667mhz.

That is, unless you plan to upgrade the CPU to a 1600mhz FSB model in the
future.

I personally wouldn't pay extra for the 800mhz RAM under your example.

hth

Stew

"S.Lewis" <> wrote in message
news:5y3kj.58670$. ..
>
> "Daddy" <> wrote in message
> news:. ..
> Thank you for that. I don't know why I didn't see it earlier (too much
> Tom's Hardware Guide).
>
> A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum
> throughput of 10,664 MB/sec. (on paper at least), which is a good match
> for 667 MHz DDR2-SDRAM (= 333 MHz double-pumped) that has a maximum
> throughput of 10,672 MB/sec in dual channel.
>
> Let me give a specific example: One computer I'm looking at is the
> Inspiron 530 desktop. The Core 2 Duo E6550 offers the fastest FSB
> available for this Inspiron, at 1333 MHz, which can achieve a maximum
> throughput of 10,664 MB/sec (as above). Why then would Dell offer 800 MHz
> DDR2 dual channel RAM - with a maximum throughput of 12,800 MB/sec - for
> this computer? What's the point - bragging rights? That's the part I don't
> get.
>
> Daddy
>
>
> The answer is really simple: supply and demand as well as costs.
>
> As quickly as speeds improve and move upward, it's entirely possible that
> Dell can purchase (at a given time) the 800mhz as cheaply as the 667mhz
> DDR2 RAM.
>
> In the past, an example of this would be, say, a Pentium 4 /2.4GHz/400mhz
> FSB CPU system that could only utilize RAM speeds of up to 266mhz
> (PC2100), but was built and shipped with 333mhz (PC2700) DDR.
>
> Why? Because as speeds and production of the RAM continually move upward
> and forward, the 333mhz was likely more plentiful and perhaps even
> cheaper - even though it will only run at the 266mhz rate in the example
> machine. They usually did this at no extra charge.
>
> Now in your example, if you're facing an optional UPcharge for the 800mhz
> RAM, it would be pointless to pay more for the 800mhz option since the CPU
> is operating at 667mhz.
>
> That is, unless you plan to upgrade the CPU to a 1600mhz FSB model in the
> future.
>
> I personally wouldn't pay extra for the 800mhz RAM under your example.
>
> hth
>
> Stew
>
>
>


PS: and I'm actually wrong on my example. The 400mhz FSB would, in fact,
not utilize RAM faster than 200mhz (PC1600) RAM, but the idea is the same.

In article <fmq87v$kgm$>, says...
> A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum
> throughput of 10,664 MB/sec. (on paper at least), which is a good match for
> 667 MHz DDR2-SDRAM (= 333 MHz double-pumped) that has a maximum throughput
> of 10,672 MB/sec in dual channel.
>
> Let me give a specific example: One computer I'm looking at is the Inspiron

Interesting and something I had never heard about before.

Could you repeat your analysis for a XPS 420 I am considering to
replace my 8250?

Either Quad,. 2.4Ghz, 1066 FSB or Duo, 3.0Ghz, 1333FSB
paired with
Either 4G at 667MHZ or 4G at 800MHz?

In each case the second choice costs more -- I now wonder if the extra
memory speed is worth the price bump because of what you said.

I am also curious about the comparison between the Quad and the faster
Duo (a slight bump in price).
--
R. Dale Shipp
spam_catcher3 (at) _delete_this_comcast (dot) net

is this also true for amd processors,i have a 64x2 5600 2.8mhz,i was told
800 mhz ram would run at full speed
"S.Lewis" <> wrote in message
news:aB3kj.58672$.. .
>
> "S.Lewis" <> wrote in message
> news:5y3kj.58670$. ..
>>
>> "Daddy" <> wrote in message
>> news:. ..
>> Thank you for that. I don't know why I didn't see it earlier (too much
>> Tom's Hardware Guide).
>>
>> A processor with a 1333 MHz FSB (= 333 MHz quad-pumped) has a maximum
>> throughput of 10,664 MB/sec. (on paper at least), which is a good match
>> for 667 MHz DDR2-SDRAM (= 333 MHz double-pumped) that has a maximum
>> throughput of 10,672 MB/sec in dual channel.
>>
>> Let me give a specific example: One computer I'm looking at is the
>> Inspiron 530 desktop. The Core 2 Duo E6550 offers the fastest FSB
>> available for this Inspiron, at 1333 MHz, which can achieve a maximum
>> throughput of 10,664 MB/sec (as above). Why then would Dell offer 800 MHz
>> DDR2 dual channel RAM - with a maximum throughput of 12,800 MB/sec - for
>> this computer? What's the point - bragging rights? That's the part I
>> don't get.
>>
>> Daddy
>>
>>
>> The answer is really simple: supply and demand as well as costs.
>>
>> As quickly as speeds improve and move upward, it's entirely possible that
>> Dell can purchase (at a given time) the 800mhz as cheaply as the 667mhz
>> DDR2 RAM.
>>
>> In the past, an example of this would be, say, a Pentium 4 /2.4GHz/400mhz
>> FSB CPU system that could only utilize RAM speeds of up to 266mhz
>> (PC2100), but was built and shipped with 333mhz (PC2700) DDR.
>>
>> Why? Because as speeds and production of the RAM continually move upward
>> and forward, the 333mhz was likely more plentiful and perhaps even
>> cheaper - even though it will only run at the 266mhz rate in the example
>> machine. They usually did this at no extra charge.
>>
>> Now in your example, if you're facing an optional UPcharge for the 800mhz
>> RAM, it would be pointless to pay more for the 800mhz option since the
>> CPU is operating at 667mhz.
>>
>> That is, unless you plan to upgrade the CPU to a 1600mhz FSB model in the
>> future.
>>
>> I personally wouldn't pay extra for the 800mhz RAM under your example.
>>
>> hth
>>
>> Stew
>>
>>
>>
>
>
> PS: and I'm actually wrong on my example. The 400mhz FSB would, in fact,
> not utilize RAM faster than 200mhz (PC1600) RAM, but the idea is the same.
>
>
>
>

"Tony Pacc" <> wrote in message
news:479123a4$0$22574$...
> is this also true for amd processors,i have a 64x2 5600 2.8mhz,i was told
> 800 mhz ram would run at full speed


Tony,

Have no idea sir. My resources and experiences have been limited to mostly
Intel stuff.

My understanding is that the memory controller is actually resident/onboard
the AMD chips versus the MCH on Intel motherboards.

I wouldn't be surprised if AMD chips/boards could run the RAM speeds
independently, but you might want to verify that online.

I'd intended to build an AMD system the next I built for myself but I ended
up putting it off.


Stew