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explain the FSB theory to me....why does double-pumped or quadruple-pumped matter?
- Thread starter luvya
- Start date
soulm4tter
Senior member
well it allows the bus to send/receive data at 2X or 4X the amount. It must be easier than actually increasing the physical speed of the bus. I'm wondering when we'll get QDR SDRAM..........:Q
The Athlon FSB is 100 or 133MHz. The clock signal is in the shape of a sine wave. Data is sent on both the rising and falling edge of the clock cycle, effectively sending data twice for one wavelength.
This results in an FSB that is equivalent to 200 or 266MHz.
This results in an FSB that is equivalent to 200 or 266MHz.
Assume a 16bit bus width for examples.
Until relatively recently in the electronics world data could only be sent on the rising edge of the clock signal (sine wave). Data sent per clock 16bits.
In a double-pumped bus data is sent on both the rising and falling edge of the clock signal (sine wave). Data sent per clock 32bits.
In a quad-pumped bus (like the bus Intel uses the P4 with). Data is sent on both the rising and falling edge of the clock signal (sine wave) and the width of the bus is twice as large (ie: 32bits instead of 16bits). Therefore twice the data can be sent on each edge of the clock signal effectively quadrupelling the data capacity of the bus. Data sent per clock 64bits.
This is a simplified explanation so Senior/Elites (anyone) don't bother picking at it.
Thorin
Until relatively recently in the electronics world data could only be sent on the rising edge of the clock signal (sine wave). Data sent per clock 16bits.
In a double-pumped bus data is sent on both the rising and falling edge of the clock signal (sine wave). Data sent per clock 32bits.
In a quad-pumped bus (like the bus Intel uses the P4 with). Data is sent on both the rising and falling edge of the clock signal (sine wave) and the width of the bus is twice as large (ie: 32bits instead of 16bits). Therefore twice the data can be sent on each edge of the clock signal effectively quadrupelling the data capacity of the bus. Data sent per clock 64bits.
This is a simplified explanation so Senior/Elites (anyone) don't bother picking at it.
Thorin
OC'ers benefit the most. Since OCing 10Mhz will yield a 20MHz gain in the FSB, but only have the impact of a 10MHz OC on the PCI/AGP buses. I found that raising the FSB on an Athlon XP 1700 just a little can make it outperform a P4 2GHz! This is possibly due to this, and the fact that the XP scales different. IE; you don't have to raise the CPU clock a whole 100MHz to jump from an XP 1700 to an 1800.
dullard
Elite Member
Try it in an analogy. Suppose you had a pile of apples sitting in a field - and you wanted the apples sent to a factory 5 miles away to make applesauce.
When you first started working on the apple shipments you picked up 1 apple and walked to the factory. Then you walked home and repeated - the whole process took you 1 hour. Thus your frequency is 1 apple/hour. Sure the task was completed, but it sure took a long time.
At next years harvest you had a great idea - bring along 7 friends. Thus all eight of you each pick up 1 apple and walk it to the factory. This was a huge improvement, your frequency is 8 apples/hour.
Again you wanted to go faster. So with the next years harvest you gathered every friend you had (15, you aren't too popular). All 16 of you walk one apple at a time to the factory: net 16 apples/hour. You cannot go any faster using this method since you are at your capacity; no more friends are available. Don't fret, you have a good idea up your sleeve.
The next years harvest all 16 of you hop into 16 trucks and drive the apples (1 at a time) to the factory. This is a huge breakthrough in increased frequency. Each of you can bring 8 apples in an hour (8 trips; you broke the speed limit a little...) The net result is 128 apples/hour! Trying to go any faster is now really difficult - sure you could purchase helicopters or build a high speed train but those options are just too expensive. I guess you are stuck: no more friends (bus width) and no faster vehicles (bus speed) are practical.
Yes! You came up with another breakthrough. Since each of you have 2 hands, why not bring two apples on each trip? This double-pump is an instant and free speed boost: 256 apples/hour.
When you first started working on the apple shipments you picked up 1 apple and walked to the factory. Then you walked home and repeated - the whole process took you 1 hour. Thus your frequency is 1 apple/hour. Sure the task was completed, but it sure took a long time.
At next years harvest you had a great idea - bring along 7 friends. Thus all eight of you each pick up 1 apple and walk it to the factory. This was a huge improvement, your frequency is 8 apples/hour.
Again you wanted to go faster. So with the next years harvest you gathered every friend you had (15, you aren't too popular). All 16 of you walk one apple at a time to the factory: net 16 apples/hour. You cannot go any faster using this method since you are at your capacity; no more friends are available. Don't fret, you have a good idea up your sleeve.
The next years harvest all 16 of you hop into 16 trucks and drive the apples (1 at a time) to the factory. This is a huge breakthrough in increased frequency. Each of you can bring 8 apples in an hour (8 trips; you broke the speed limit a little...) The net result is 128 apples/hour! Trying to go any faster is now really difficult - sure you could purchase helicopters or build a high speed train but those options are just too expensive. I guess you are stuck: no more friends (bus width) and no faster vehicles (bus speed) are practical.
Yes! You came up with another breakthrough. Since each of you have 2 hands, why not bring two apples on each trip? This double-pump is an instant and free speed boost: 256 apples/hour.
soulm4tter
Senior member
how about everybody carry a bucket which holds 16 apples next year, then we'll have 2048 apples/hour.................woot!
dullard
Elite Member
<< how about everybody carry a bucket which holds 16 apples next year, then we'll have 2048 apples/hour.................woot! >>
Were going that way. The P4 is quad-pumped and quad rate SDRAM is being developed. I kept my example to two apples since we have two hands. It is much more difficult to carry 4, 8, 16 apples than just two. The same holds with computer parts. It isn't very easy to just go to a 16-pumped fsb... That would be interesting to see though.
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