internal speed is high, external speed is low!!

Hi
I do not see in this scenario that why we need high speed memory..

If we have Athlon XP1800 which is using:

11.5 multiplier X 133MHz FSB and if we have DDR266

I understand that the speed of the memory is 266Mhz but the CPU can
communicate with the Memory using FSB speed which is 133. I can
imagine this like a highway connect 2 city one city called CPU which
allow internal traffic at speed 1533 AND another city which is called
"Memory" which allows the internal traffic at speed 266MHz. Now if a
car want to travel from CPU to Memory it can only drive at max speed
which is 133Mhz. Now my question is, what is the point that I have
internal speed of both the CPU and Memory high when the external road
is low 133Mhz.I thought the FSB speed should be high so information
can traval faster between CPU and Memory or any other part of the PC.

Any help would be very much appreciated.

"esara" wrote in message
m...
Hi
I do not see in this scenario that why we need high speed memory..

If we have Athlon XP1800 which is using:

11.5 multiplier X 133MHz FSB and if we have DDR266

I understand that the speed of the memory is 266Mhz but the CPU can
communicate with the Memory using FSB speed which is 133.

You are forgetting that the DDR is dual data rate. Thus, 266 is clocked
externally at 133, the same as your FSB. But it actually makes no
difference at all, as most (all?) modern chipsets can run your memory at any
speed up to maximum supported by the chipset, whether it matches the FSB or
not. For best performance (read: max benchmark speeds), it's best to have
the RAM match the CPU. Thus, 166 CPU would use DDR333 RAM and so on. But
that 166CPU would be perfectly happy with DDR400 RAM, also. If the chipset
supports it, the DDR400 can run at DDR400, or it will just run at DDR333
(slightly underclocked) if that's all the chipset can do. -Dave

What none of can figure out is what gave you idea that the 1800+ XP only
allows a 133MHz FSB.
Every 1800+ data sheet I have from AMD says that the 1800+ allows a 266MHz.
FSB, and thats were you are running it.

JPS

"esara" wrote in message
m...
Hi
I do not see in this scenario that why we need high speed memory..

If we have Athlon XP1800 which is using:

11.5 multiplier X 133MHz FSB and if we have DDR266

I understand that the speed of the memory is 266Mhz but the CPU can
communicate with the Memory using FSB speed which is 133. I can
imagine this like a highway connect 2 city one city called CPU which
allow internal traffic at speed 1533 AND another city which is called
"Memory" which allows the internal traffic at speed 266MHz. Now if a
car want to travel from CPU to Memory it can only drive at max speed
which is 133Mhz. Now my question is, what is the point that I have
internal speed of both the CPU and Memory high when the external road
is low 133Mhz.I thought the FSB speed should be high so information
can traval faster between CPU and Memory or any other part of the PC.

Any help would be very much appreciated.

"jpsga" wrote in message
news:P2%cc.211470$_w.1986831@attbi_s53...
What none of can figure out is what gave you idea that the 1800+ XP only
allows a 133MHz FSB.
Every 1800+ data sheet I have from AMD says that the 1800+ allows a
266MHz.
FSB, and thats were you are running it.

JPS

http://www.ultimatehardware.net/xpchart/xpchart.htm

"jpsga" wrote in message
news:P2%cc.211470$_w.1986831@attbi_s53...
What none of can figure out is what gave you idea that the 1800+ XP only
allows a 133MHz FSB.
Every 1800+ data sheet I have from AMD says that the 1800+ allows a
266MHz.
FSB, and thats were you are running it.

JPS


That's marketing hype. The XP1800 runs at 133FSB, 266DDR.


bluestringer

Howdy!

"esara" wrote in message
m...
Hi
I do not see in this scenario that why we need high speed memory..

If we have Athlon XP1800 which is using:

11.5 multiplier X 133MHz FSB and if we have DDR266

I understand that the speed of the memory is 266Mhz but the CPU can
communicate with the Memory using FSB speed which is 133. I can
imagine this like a highway connect 2 city one city called CPU which
allow internal traffic at speed 1533 AND another city which is called
"Memory" which allows the internal traffic at speed 266MHz. Now if a
car want to travel from CPU to Memory it can only drive at max speed
which is 133Mhz. Now my question is, what is the point that I have
internal speed of both the CPU and Memory high when the external road
is low 133Mhz.I thought the FSB speed should be high so information
can traval faster between CPU and Memory or any other part of the PC.

Any help would be very much appreciated.

Dave C. explained part of it pretty good. But there's another
portion - if the CPU is using 100% of the memory bandwidth, exactly WHEN
does the HD / floppy / sound / video / et al get access to it? B-)

In a perfect world, we could run the RAM at 2x the CPU speed, so
that the CPU got it half the time and the rest of the world the other half.

Matter of fact, that was the primary initial design point behind DDR
on the processor - one half the clock for RAM, one half for I/O. Didn't
stay that way ...

RwP

On 7 Apr 2004 10:09:49 -0700, (esara) wrote:

Hi
I do not see in this scenario that why we need high speed memory..

If we have Athlon XP1800 which is using:

11.5 multiplier X 133MHz FSB and if we have DDR266

I understand that the speed of the memory is 266Mhz but the CPU can
communicate with the Memory using FSB speed which is 133.

- No, no, and no again, basically.
The speed of the memory bus is not 266MHz. The bus frequency is
133MHz, the DDR (double data rate) speed is 266, that's why it's
called DDR266. (Don't ask me how it works. Please feel free to
explain, if anybody knows the details of DDR. I could guess, it's
something similar to the EV6 bus?)

The CPU does not communicate directly with memory. It communicates
with the 'Northbridge' part of the chipset, which contains the memory
controller and connects to ram via the memorybus (133MHz), and also
connects to AGP and Southbridge(PCI, IDE and other).

The FSB speed is 266MHz! The FSB-_CLOCK_ is 133MHz.
....And the (AMD&Athlon) Alpha EV6 protocol FSB effective speed is
266MHz on a 133MHz clock. (The EV6 bus doesn't bother with any
multiplier, like the CPU, it simply syncs transfer enables, on BOTH
rising and falling flank of the clock, so the bus speed is TWICE the
clock).
The FSB-CLOCK is highly visible in BIOS. Often it's also called simply
FSB, in many bios'es, instead of 'fsb-clock' or 'external-clock'. Thus
a lot of people assume this is the bus speed. (and possibly becomes a
bit confused about processor-, chipset-specs)
It's very common that people in this group says things like "set your
FSB to 166MHz". Now that happens to be 'short' form, and what they
really says is: "set your FSB _clock_ to 166MHz, and thus your FSB
_speed_ to 333MHz".
It's also common that people confuses front side bus and memory bus.

[CPU]
|
fsb 133 clock = 266MHz speed
|
[Northbridge]
|
memorybus 133MHz = 266DDR speed
|
[RAM]

So basically we have in both cases some kind of synchronization, that
runs at 133MHz, but both the actual data transfer speeds are 266MHz.

We don't have to have precisely that configuration. The FSB and
memorybus can run on different frequencies. You basically want as fast
FSB as possible. But the normal AMD case nowadays, is that the
available DDR speed is as high or higher than the available fsb speed.
And in this case, the general recommendation is to run FSB and
memorybus in sync. (That is: lowering the memory speed to match FSB. -
Don't lower FSB to match memory. If you can run FSB faster, - do so!)

Examples:
You have an AthlonXP with 333MHz FSB. You also have PC3200 ram, which
can run at DDR400. Run the ram at DDR333, to be more stable and to run
in sync with the FSB.

You have an AthlonXP with 333MHz FSB. You also have PC2100 ram, which
can run at DDR266. Run the ram at DDR266 and the FSB asynchronously
still at 333MHz. (This is also a case where dual channel will serve
you well.)

ancra

On Wed, 7 Apr 2004 19:06:00 -0400, "bluestringer"
wrote:


"jpsga" wrote in message
news:P2%cc.211470$_w.1986831@attbi_s53...
What none of can figure out is what gave you idea that the 1800+ XP only
allows a 133MHz FSB.
Every 1800+ data sheet I have from AMD says that the 1800+ allows a
266MHz.
FSB, and thats were you are running it.

JPS


That's marketing hype. The XP1800 runs at 133FSB, 266DDR.

No it's not marketing hype. It's confusing issues, confusing memorybus
with cpu fsp, confusing clocks with speed.
The _SPEED_ of the Athlon's FSB has _never_ been lower than 200MHz!
And the FSB speed of the 1800+ is 266MHz, just like the AMD data sheet
says. No marketing hype at all about it.
And DDR or any memory speed at all, have nothing to do with the FSB.

ancra

On Wed, 7 Apr 2004 18:19:39 -0400, "Dave C."
wrote:


"jpsga" wrote in message
news:P2%cc.211470$_w.1986831@attbi_s53...
What none of can figure out is what gave you idea that the 1800+ XP only
allows a 133MHz FSB.
Every 1800+ data sheet I have from AMD says that the 1800+ allows a
266MHz.
FSB, and thats were you are running it.

JPS

http://www.ultimatehardware.net/xpchart/xpchart.htm

Yes, Dave, but the original poster was talking about speeds.
That table lists clocks.

ancra

On Thu, 08 Apr 2004 03:46:34 +0200, in wrote:

memorybus 133MHz = 266DDR speed

.... & @ same mem clock (effective), the DDR is practically only 10%
approx. in real life faster (theoretical max bandwith is double in
SiSoft Sandra for example)

so best real life performance bench between different platforms for
compares, is to use incorporated mem subsistem bench in WinRAR;
for example I get 315 points (index) on my Sdram @ 135fsb/mem clock...

--
Regards, SPAJKY ®
& visit my site @ http://www.spajky.vze.com
"Tualatin OC-ed / BX-Slot1 / inaudible setup!"
E-mail AntiSpam: remove ##