What determines your FSB setting?

[Wes Newell]

Sorry I also forgot to ask about the DDR memory .. can we say that the
"actual speed or clock speed of DDR memory is 1/2 the effective
speed". I mean if the DDR is 333Mhz then the actual speed is 333/2 and
if DDR is 266 (which is the effective speed) then the actual speed is
266/2. Can I say so??
Thanks..

Why even bother with "effective speed". It's bascally a worthless
statement without knowing what you are comparing the efectiveness to.
Some examples:
A P4/800 only has an effective speed of 400MHz when compared to an Athlon
200MHz (or is that 400MHz effective) FSB cpu.
So I could say an Athlon/400 has an effective FSB speed of 400MHz and the
P4/800 also has an effective FSB speed of 400MHz and be completely
correct.
And that just one more reason the CPU FSB speed is measured in clock
cycles, not data rates.
And until you admit to ones self that the numbers are just bogus BS, you
will continue to have this confusion.
Bus clocks are measured in Hz, data rates aren't, and never should the two
be intertwined.

 

[Wes Newell]

Thank you. I thought I remembered having seen that (decimal) stated
before somewhere, but I wasn't sure.

That means 'MHz' and 'Mbps per bit' are exactly the same unit for
frequency. (I prefer MHz And Mbps is something different,
troughput, rather than frequency)

No it doesn't mean anything of the sort. Hz is used for a clock cycle. A
clock cycle is constant. Bps means bits per second. This could be constant
or not. It doesn't have a consant cycle from low to high as does the clock.

But it also means things like:

"MB per second" is not the same as "MBps". Interesting observation, I
think.

Huh! Both mean MegaBytes per second. In data throughput M is always 1
million. Actaully, it probably properly MiliBytes, but everyone uses the
former.

 

[Wes Newell]

The cpus are marketed with their 'effective FSB speed'. That's how you
buy them. The 'FSB clock speed' is what you need to set the mobo FSB
clock to.
(There's other older P4s and Athlons too, other than those I listed.)

So this kinda makes the so called efective speed pretty much worthless.

"actual FSB speed" I don't understand. Please keep to "effective" or
*clock* respectively. Both are actual and real. FSB Clockspeed is the
frequency of the clock that syncs transfers. Effective FSB speed is the
frequency of transfers.

Let me help you. Actual means real. FSB means Front Side Bus. And speed
means the clock speed. Now you know.

The Intel P4 varieties (P4B, P4C, P4E and P4EE) with 533 and 800 MHz
FSB, have what Intel call a "quad pumped" bus. This means the transfers
can occur 4 times per clock cycle. So 4 * 200 = 800 and 4 * 133 = 533.

I think everyone that reads this uderstand the Intel bus. I prefer QDR for
Quad Data Rate, which is more precise than quad pumped, which sounds like
you're at a gas station pumping gas instead of data.

AMD is using DEC's old Alpha bus. This syncs on both rise and fall of
clock. So effective speed is simply twice that of the clock.

DDR would have done here.

 

[somebody]

No it doesn't mean anything of the sort. Hz is used for a clock cycle. A
clock cycle is constant. Bps means bits per second. This could be constant
or not. It doesn't have a consant cycle from low to high as does the clock.

(Bps means bytes per second, ...and I know you were starting a new
sentence )
I didn't say 'bps' I said 'bps p b', which was your construct, I
believe. Personally, I find that *datawidth per datawidth* a somewhat
contorted effort to hide the fact that we're really dealing with s^-1.

As for MHz:
The nomenclature used by AMD and Intel in their specs and in their
technical documentation, is: "800MHz bus", "800MHz speed", "800MHz
FSB" etc, " _off_ a 200MHz system clock", " - 200MHz bus clock" etc.
This is also the nomenclature used by chip set and mobo manufacturers,
when referring to supported features.
It's also the nomenclature used by distributors, retailers and media,
and so on.
"Effective speed" is (again) _not_ data rate. And it is always
measured in MHz, whether you think it's appropriate or not. And MHz is
a unit for frequency. SI definition being 10^6 * s^-1. (Which does
seem appropriate enough to me, apples being apples.)

Huh! Both mean MegaBytes per second. In data throughput M is always 1
million. Actaully, it probably properly MiliBytes, but everyone uses the
former.

Well, thank you again, I take that to mean that I can usually depend
on M being decimal in any troughput figure.

ancra

 

[somebody]

I think everyone that reads this uderstand the Intel bus.

(?) ...I assumed esara asked.

I prefer QDR for
Quad Data Rate, which is more precise than quad pumped, which sounds like
you're at a gas station pumping gas instead of data.

Ok, the nomenclature Intel is using, in their technical documentation
is "quad pumped", so I'll just stick to that, for the sake of
consistency.

DDR would have done here.

Would it? Then I'd have to be clear about not meaning DDR ram etc.
....No Wes, there was a smilie on that, but reign your horses.

ancra

 

[somebody]

Why even bother with "effective speed".

Because it's all over the place. In sales specs, in technical
documentation, in media, on cpu markings. But usually nobody even
bothers much about "effective". Even Intel and AMD are mostly just
simply stating "bus speed" or "FSB speed". Even in their technical
manuals. - And no, it's not the clock speed they're referring to.

It's bascally a worthless
statement without knowing what you are comparing the efectiveness to.

Fundamentally, everything is worthless if you don't have a purpose for
it. Fundamentally, every purpose requires additional knowledge.
Anyone trying to set his FSB clock to AMD/Intel advertised "FSB speed"
has been misled.
Anyone not understanding why dual channel DDR400 makes sense for his
P4C, since it has only got a "200MHz bus clock" has also been misled.

Some examples:
A P4/800 only has an effective speed of 400MHz when compared to an Athlon
200MHz (or is that 400MHz effective) FSB cpu.
So I could say an Athlon/400 has an effective FSB speed of 400MHz and the
P4/800 also has an effective FSB speed of 400MHz and be completely
correct.

No, that's only you fooling around with what you think should or could
be the meaning of "effective bus speed". I think that AMD and Intel
intend it to mean frequency of transfers.

And that just one more reason the CPU FSB speed is measured in clock
cycles, not data rates.
And until you admit to ones self that the numbers are just bogus BS, you
will continue to have this confusion.
Bus clocks are measured in Hz, data rates aren't, and never should the two
be intertwined.

(But effective bus speed is clearly _not_ exactly data rate. It's a
different property (a frequency, - virtual or real), even if it's
closely related to data rate.)

In your opinion, if I got you right, you feel AMD and Intel should
have spec'ed their FSBs with max data rate instead? Fair enough, that
argument has some merit IMO, but that's not the way things are now.

ancra

 

[Wes Newell]

As for MHz:
The nomenclature used by AMD and Intel in their specs and in their
technical documentation, is: "800MHz bus", "800MHz speed", "800MHz
FSB" etc, " _off_ a 200MHz system clock", " - 200MHz bus clock" etc.

Can't say what Intel says, but AMD's data sheets use the clock speed to
describe the system bus, not the so called effective speed either. IOW's,
nowhere in the doc do they call 333FSB, 333MHz FSB. They do use 166MHz for
it though with a note that bus operrates at twice the clock speed. No
other details are given. And even if they did, it wouldn't matter, it
would just be wrong.

This is also the nomenclature used by chip set and mobo manufacturers,

Hmmm.... There's no FSB setting anywhere close to 333, much less 400 in
the bios of any board I've used. They use the real speed too. My latest
board is an Athlon 64 board. Top FSB speed in it is 233Mhz.

when referring to supported features. It's also the nomenclature used by
distributors, retailers and media, and so on. "Effective speed" is
(again) _not_ data rate. And it is always measured in MHz, whether you
think it's appropriate or not. And MHz is a unit for frequency. SI
definition being 10^6 * s^-1. (Which does seem appropriate enough to me,
apples being apples.)

You can say the moon is made of green cheese too.

 

[Wes Newell]

In your opinion, if I got you right, you feel AMD and Intel should
have spec'ed their FSBs with max data rate instead? Fair enough, that
argument has some merit IMO, but that's not the way things are now.

That would be fine, but that's not what it's about. It's about the bogus
MHz numbers. These numbers are virually worthless. You can't use them for
anything. You can't use these numbers in their native state to determine
anything. Not the multiplier, nothing. Lets assume someone doesn't know
how the system bus works. IOW's a typical newbie trying to build a system
that has absolutely no experience with anything past a K6 model cpu where
the data rate macthes the FSB speed. To them the FSB setting is the clock
rate. So now he goes into the bios to set the FSB clock and he can't find
a 400Mhz setting. But the ads say it's a 400 or 800Mhz FSB so he's lost.
Now he has to go find out that the numbers are just BS, and he has to
divide them by 2 or 4 to get The Real Front Side Bus speed to set up his
machine properly or to determine the actual cpu speed.. So tell me just
what are these numbers good for. Cite just one instance where they are
really needed to configure anything. Can't find one?

They are nothing but bogus BS marketing crap. They don't give the user
anything except false information. Most user couldn't even fnd the real
data rate throughput with them.

 

[Erez Volach]

So this kinda makes the so called efective speed pretty much worthless.

Let me help you. Actual means real. FSB means Front Side Bus. And speed
means the clock speed. Now you know.

I think everyone that reads this uderstand the Intel bus. I prefer QDR for
Quad Data Rate, which is more precise than quad pumped, which sounds like
you're at a gas station pumping gas instead of data.

DDR would have done here.

9,600 bps modems had 2400 baud signalling with 4 bit-wide "word", this is
analogous to "QDR" sending data 4 times fold the signalling rate. Using a
MegaHertz unit is meaningfull when you state what is it that completing a
"cycle" or "phase".

 

[somebody]

Can't say what Intel says, but AMD's data sheets use the clock speed to
describe the system bus, not the so called effective speed either. IOW's,
nowhere in the doc do they call 333FSB, 333MHz FSB.

I only checked Intel, but I didn't have to check AMD (...or so I
thought):
AMD Athlon XP processor
Page 1 model 6 data sheet, Overview, 6 lines from bottom.

However, just as I was about to to rub your nose in this ;-), I
noticed to my horror that in _later_ model data sheets, the MHz unit
is gone:
Page 2 model 8 data sheet, Overview, 3, 4 and 26 lines from top.
Page 2 model 10 data sheet, Overview, 3 to 5 lines from top.
Here it's just "333 FSB" and "400 FSB".
(So, this is most frustrating and annoying )

But still, not only do these data sheets consistently use "266/333/400
FSB" , riffling through, I can't see the clock ever being referred to
as "bus speed". It's always called system clock or bus clock.
In tables like in chapter 6, page 22 and chapter 7 page 26, for
instance, we see that "maximum clock frequency" is indeed 166MHz and
200MHz for "333 FSB sysclk and sysclk# AC characteristics" and "400
FSB" respectively.

Hmmm.... There's no FSB setting anywhere close to 333, much less 400 in
the bios of any board I've used.

....Since it's the clock you set. However, mobo manuals state things
like 266, 333, 400 MHz FSB in specs etc. However, you know that too,
so you're just being argumentative ;-).

They use the real speed too. My latest
board is an Athlon 64 board. Top FSB speed in it is 233Mhz.

That's neat, since the A64 doesn't have any FSB. ;-)
(I bet it has an external clock though.)

ancra

 

[somebody]

So now he goes into the bios to set the FSB clock and he can't find
a 400Mhz setting. But the ads say it's a 400 or 800Mhz FSB so he's lost.
Now he has to go find out that the numbers are just BS, and he has to
divide them by 2 or 4 to get The Real Front Side Bus speed...

Or perhaps more correctly and certainly less confusing: 'bus clock
speed'.;-)

...to set up his
machine properly or to determine the actual cpu speed.. So tell me just
what are these numbers good for. Cite just one instance where they are
really needed to configure anything. Can't find one?

Nonsense, they're needed for calculating your bus clock ;-)
....And your memory bus clock ;-)
But I think you're on to a "bogus" point here. It's a game that can
never be won. Knowledge is always required:
Consider the reverse, someone asking why use DDR333 ram with a 'slow'
166MHz FS bus.

You simply have to understand that it's the external clock you're
setting. Calling that clock "FSB speed" (which is in widespread use
for a different thing) is not going to reduce confusion or make it
simpler for people.

They are nothing but bogus BS marketing crap. They don't give the user
anything except false information.

The information is not false unless you interpret it as something it
isn't. It gives the user an idea of how fast the bus can transfer
data.

ancra