PCI vs. AGP 8x?

  • Thread starter Thread starter Alien
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The said:
It's the frequency it runs at, not the throughput. WTF would it say
100mhz if it doesn't run at a frequency of 100mhz? Is the mb
manufacturer on drugs or are you?
Click to expand...

I have no idea why the motherboard manufacturer would claim that.
Presumably they're running _something_ at that speed, but that something is
_not_ the PCI Express lanes themselves.

Why is it that you are having so much trouble grasping that it is not
possible to move 2 billion bits per second down a single pair using 8/10B
encoding at 100 MHz? You keep saying that "it's the throughput". Well,
with a single pair, using 8/10B encoding at 100 MHz, you get 80 Mb/sec
throughput, not 2 billion.
 
Why is it that you are having so much trouble grasping that it is not
possible to move 2 billion bits per second down a single pair using 8/10B
encoding at 100 MHz? You keep saying that "it's the throughput". Well,
with a single pair, using 8/10B encoding at 100 MHz, you get 80 Mb/sec
throughput, not 2 billion.
Click to expand...


http://www.directron.com/a8nslid.html
PCIe Frequency: allowing PCIe frequency from 100MHz up to 200MHz at
1MHz increment.


http://www.digit-life.com/articles2/mainboard/abit-fatal1ty-aa8xe-i925xe.html
PCI/PCI-E frequency divider setup
PCI-E = Auto, 99 - 255 MHz at 1 MHz steps
PCI = 33.33 MHz, 36.36 MHz, 40.00 MHz, Auto (modify in accord with the
PCI-E frequency), CPU (modify in accord with the FSB frequency)

http://www.msi.com.tw/html/service/techexpress/mainboard/7160/page2.htm
PCIE Frequency (MHz):
Its adjustable range from standard maximum is 100MHz to 148MHz. Please
aware that any adjustment over 110MHz may cause your VGA card damaged.
 
The said:
http://www.directron.com/a8nslid.html
PCIe Frequency: allowing PCIe frequency from 100MHz up to 200MHz at
1MHz increment.


http://www.digit-life.com/articles2/mainboard/abit-fatal1ty-aa8xe-i925xe.html
PCI/PCI-E frequency divider setup
PCI-E = Auto, 99 - 255 MHz at 1 MHz steps
PCI = 33.33 MHz, 36.36 MHz, 40.00 MHz, Auto (modify in accord with the
PCI-E frequency), CPU (modify in accord with the FSB frequency)

http://www.msi.com.tw/html/service/techexpress/mainboard/7160/page2.htm
PCIE Frequency (MHz):
Its adjustable range from standard maximum is 100MHz to 148MHz. Please
aware that any adjustment over 110MHz may cause your VGA card damaged.
Click to expand...

I've already posted numerous links to sources far more authoritative than
any of those that say otherwise. And you have still not explained how they
accomplish what you claim that they accomplish. Further, it is
increasingly clear that you have not the slightest clue how PCI Express
works or what it is, other than a name.
 
I've already posted numerous links to sources far more authoritative than
any of those that say otherwise. And you have still not explained how they
accomplish what you claim that they accomplish. Further, it is
increasingly clear that you have not the slightest clue how PCI Express
works or what it is, other than a name.
Click to expand...

Those are mb manufacturer links, explain why they give a frequency for
PCI-E if you say one doesn't exist.

And you are wrong about what I know.

http://www.computerforum.com/showthread.php?t=13239
PCI Express. Formerly known as 3GIO, also denoted as PCIe, this is an
extremely highspeed serialized interface. The individual serial lanes
can be grouped together and when done as such, they are denoted as
PCIxN where N is the number of lanes that are grouped together. Each
lane is capable of 250MB/s
 
The said:
Those are mb manufacturer links, explain why they give a frequency for
PCI-E if you say one doesn't exist.
Click to expand...

Liar.

I did not say that "one does not exist". I said that the frequency that
they were specifying was not for the PCI Express lanes, which run at 2.5
GHz.
And you are wrong about what I know.

http://www.computerforum.com/showthread.php?t=13239
PCI Express. Formerly known as 3GIO, also denoted as PCIe, this is an
extremely highspeed serialized interface. The individual serial lanes
can be grouped together and when done as such, they are denoted as
PCIxN where N is the number of lanes that are grouped together. Each
lane is capable of 250MB/s
Click to expand...

Which proves that you can cut and paste, not that you have the tiniest iota
of understanding of what you have read. You still have not explained how
one can get 2 Gb/sec out of a 100 MHz signal using 8/10B encoding on a
single pair.
 
J. Clarke said:
The Outsider wrote:




Liar.

I did not say that "one does not exist". I said that the frequency that
they were specifying was not for the PCI Express lanes, which run at 2.5
GHz.




Which proves that you can cut and paste, not that you have the tiniest iota
of understanding of what you have read. You still have not explained how
one can get 2 Gb/sec out of a 100 MHz signal using 8/10B encoding on a
single pair.
Click to expand...

The lanes are in fact LVDS signaling schemes (lanes are limited to 20
inches by spec) that yell at each other at 2.5 Gbps (that's Gigabits per
second or 250 MegaBytes per second). The 100 MHz clock is usually a
reference clock (on pins 13 and 14 on side A of the connector).

Technically the clock for RX and TX are embedded in the signaling scheme
in which they communicate with each other. However, when the
transmitter runs in spread-spectrum for EMI purposes the receiver needs
the common clock (which is usually the 100MHz ref...)

The interesting inclusion of spread-spectrum clock generation for PCs
can be seen here (under "Spread-spectrum clock generation"):
http://en.wikipedia.org/wiki/Spread_spectrum

Another good link that shows the way that spread spectrum works and why
mobo folks implement it:
http://zone.ni.com/devzone/conceptd.nsf/webmain/EE6BC161F0C17F0986256FEE005D3797

Unfortunately, I don't know the details of the spread-spectrum clock and
its effect on the transmission of PCIe data, but I assume it controls
how fast the transmission 'sweeps'.

Hope it helps.

SmacknRat
 
Smack'n Rat said:
The lanes are in fact LVDS signaling schemes (lanes are limited to 20
inches by spec) that yell at each other at 2.5 Gbps (that's Gigabits per
second or 250 MegaBytes per second). The 100 MHz clock is usually a
reference clock (on pins 13 and 14 on side A of the connector).

Technically the clock for RX and TX are embedded in the signaling scheme
in which they communicate with each other. However, when the
transmitter runs in spread-spectrum for EMI purposes the receiver needs
the common clock (which is usually the 100MHz ref...)

The interesting inclusion of spread-spectrum clock generation for PCs
can be seen here (under "Spread-spectrum clock generation"):
http://en.wikipedia.org/wiki/Spread_spectrum

Another good link that shows the way that spread spectrum works and why
mobo folks implement it:
http://zone.ni.com/devzone/conceptd.nsf/webmain/EE6BC161F0C17F0986256FEE005D3797

Unfortunately, I don't know the details of the spread-spectrum clock and
its effect on the transmission of PCIe data, but I assume it controls
how fast the transmission 'sweeps'.
Click to expand...

Finally someone who actually does have some clue what's going on enters the
discussion. Thank you.
 
Liar.

I did not say that "one does not exist". I said that the frequency that
they were specifying was not for the PCI Express lanes, which run at 2.5
GHz.
Click to expand...

From the links I provided one can indeed see they are specifying the
PCI-E graphics slot. Contact Asus and ask them about it.
 
Finally someone who actually does have some clue what's going on enters the
discussion. Thank you.
Click to expand...

Well, you couldn't explain the 100mhz clock on PCI-E so you know ****
all too.
 
The said:
From the links I provided one can indeed see they are specifying the
PCI-E graphics slot. Contact Asus and ask them about it.
Click to expand...

I'm sorry, but there is no statement there to the effect that the 100 MHz
clock is for any part of the signalling that is part of the PCI Express
standard, just that something related to PCI Express is clocked at that
speed.

Look, if it's so important to you that you believe something that is not
true, I'm not going to try to stop you, but when Intel and ASUS disagree on
a standard that was pretty much created by Intel and is implemented using
an Intel chip, I'll believe Intel before I'll believe ASUS.
 
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