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PCI Express 16X slot voltage? PCI Express 16X slot voltage?
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PCI Express 16X slot voltage?
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Old 31st May 2006, 22:29   #1
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Default PCIe 16X slot voltage?

Can anyone help me with this question please.

I need to know what voltages are avilable form the PCIe Slot. I understand this slot supplies 75W maximum, but at what voltage and amperes?

Second question: the 6-pin external connector, is this a stright 12V source or can the graphic card draw "up to" 12V?

For example the 12V4-Rails I know simply by mobo specifiation this external connector is limited to 18A (22A Peak for a 800W PSU) and tere's a formula for getting amperes from Wattage.

To get wattage the formula is simple:
P (Power or Watts) = volts x amperes

for amperes it seems to be watts / volts = amperes

SO what I'm getting at is, if the external power connector to a videocard is 12V and we know it's 16A then

12V x 16A = 192W ?

EDIT" JMKE the info King, found me som great info on this going to read it tonite. If anyone else is interested it'll be here.
Old 31st May 2006, 22:33   #2
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sorry for this reply not containing answers, but PCI-EX is extended PCI slots not PCI Epxress, the short name for PCI Express is PCIe

let's make reply more useful

PCI Express is the new serial bus addition to the PCI series of specifications. How ever the electrical and mechanical interface for PCI Express is not compatible with the PCI bus interface. This is a serial bus which uses two low-voltage differential LVDS pairs, at 2.5Gb/s in each direction [one transmit, and one receive pair]. A PCI Express link is comprised of these two unidirectional differential pairs each operating at 2.5Gbps to achieve a basic over all throughput of 5Gbps [before accounting for over-head]. PCI Express uses 8B/10B encoding [each 8 bit byte is translated into a 10 bit character in order to equalize the numbers of 1's and 0's sent, and the encoded signal contains an embedded clock]. PCI Express supports 1x [2.5Gbps], 2x, 4x, 8x, 12x, 16x, and 32x bus widths [transmit / receive pairs]; 2.5Gigabits/second per Lane per Direction. The 8B/10B changes the data transfer numbers to 250MBps per lane, raw data [B= Bytes, b=Bits]. The reduction in throughput is accounted for under the protocol section.
LVDS stands for: Low Voltage Differential Signaling.

The basic LVDS interface is a single differential link in either one or both directions. Each link requires a termination resistor at the far [receiver] end. The nominal resistor values used is 100 ohms, but would depend on the cable or PWB trace impedance used. LVDS is a scalable bus; one uni-directional link or multiple links may be used. The LVDS graphic above indicates a 1-meter length, but the PCIe specification only allows a 20 inch trace. Refer to the LVDS page for additional information
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Old 31st May 2006, 22:55   #3
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P (Power or Watts) = volts x amperes

for amperes it seems to be watts / volts = amperes

SO what I'm getting at is, if the external power connector to a videocard is 12V and we know it's 16A then

12V x 16A = 192W ?
it is correct from how/what I understand about electricity.


However, I'm not sure if 5 and 3.3V are required or not; if they do, they can be drawn from motherboard. The 12V 6-pin is to ensure sufficient direct power supplying to the video card rather than from the motherboard.

Opteron 165 (2) @2.85 1.42 vcore AMD Stock HSF + Chill Vent II
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Old 1st June 2006, 13:41   #4
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PCIe is what I mean. First it's important to clarify what we're discussing jmke has corrected me and I am grateful.

In fact I was writing PCIE16X which isn't necessary either because we all have to do is is be sure it's PCIe because the slot bandwidth ranges between 16 ~ 4X.
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