AGP vs PCI-E x1, x16

lhuser

Golden Master
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13,147
Why is AGP slower than PCI-E?

AGP is doubled gold fingers which the transfer should go fast while PCI-E is only one gold fingered.

Is it because the AGP 8X runs at 128 while PCI-E runs at 256 for the x16 and 128 for the x1?
 

Dishdog

Fully Optimized
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2,801
i don't think that right now PCI-E x16 is faster, they are the same. but in the future PCI-E x16 will be faster.
 

ownage

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4,404
well its called AGP 8X for a reason, and its called PCI-Express 16X for a reason, PCI-Express has double the bandwidth of AGP cuz 16X = 8X x 2.
 

DarkBlade1

BSOD
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3,355
Osak said:
Yea PCI-E allows a higher bandwith (I think not 100%) than AGP.

AGP= 16Gbits/sec

PCI Express = 2.5Gbits/sec/LANE

so...

PCI 1x= FASTER THEN PCI, but NOT AGP

PCI 16x= 2.5Gb/sec X 16= 40Gbits/sec (MUCH FASTER THEN AGP)
40Gbits/sec = 5GB/sec

So, AGP 8x= 2.1GBs/sec
PCIe 16x = 5GBs/sec

MUCH FASTER, more then double the bandwidth. The 6800GT outputs around 32GB/sec, so on a PCIe 16x BUS, that info is recieved MUCH faster then on AGP 3.0 8x. AGP is bad.. PCIe is MUCH faster.
 

PZEROFGH

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OH I SEE, how long do you think my agp card will last, its a 9800 pro?, at least a couple of years PLEASE!
 

catalyst1

BSOD
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2,734
Here's the deal - the AGP/PCI bus is shared. All AGP/PCI device data runs through the same data lines on your motherboard. This obviously makes a bottleneck situation where the devices must take turns to transmit data. Quite inefficient.

What PCIe does is allow each device their own data path. This is a giant leap in PCI bus technology, especially for video cards which transfer several gigabytes of data per second (which is why video cards were so quick to adopt the new standard). PCIe isn't just for video cards, though. Eventually PCI will be completely replaced with PCIe. This is where the different sizes come in. PCIe can come in x1, x2, x4, x8, x12, x16, and x32. I believe x64 is coming soon, but I didn't find any info on that. In any case, the numbers define the number of data paths. x1 transmits data back and forth on one data path, x16 transmits on 16 data paths, et cetera. The smaller PCIe sizes will probably be used for things like NICs, USB cards, sound cards, things like that.

Also, an answer about PCIe having fewer pins - I quoted this from one of the articles below: "In order to transmit PCIe packets, which are composed of multiple bytes, a one-lane link must break down each packet into a series of bytes, and then transmit the bytes in rapid succession. The device on the receiving end must collect all of the bytes and then reassemble them into a complete packet. This disassembly and reassembly happens must happen rapidly enough to where it's transparent to the next layer up in the stack. This means that it requires some processing power on each end of the link. The upside, though, is that because each lane is only one byte wide, very few pins are needed to transmit the data. You might say that this serial transmission scheme is a way of turning processing power into bandwidth; this is in contrast to the old PCI parallel approach, which turns bus width (and hence pin counts) into bandwidth. It so happens that thanks to Moore's Curves, processing power is cheaper than bus width, hence PCIe's tradeoff makes a lot of sense."


Here's some good reference:

http://arstechnica.com/articles/paedia/hardware/pcie.ars/1?94142
http://www.pcstats.com/articleview.cfm?articleID=1087
http://www.cooltechzone.com/index.php?option=content&task=view&id=506&Itemid=0&limit=1&limitstart=0
http://en.wikipedia.org/wiki/PCI-Express
 

catalyst1

BSOD
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2,734
PZEROFGH said:
OH I SEE, how long do you think my agp card will last, its a 9800 pro?, at least a couple of years PLEASE!
Don't worry, AGP isn't dead yet. However, it will be phased out eventually. I'd give it around five to ten years, but that's just a guess.
 

PZEROFGH

Golden Master
Messages
7,689
so if i had a agp card, and i plugged in no pci cards, it means the agp slot has the whole data pass to itself, right?

whew 5-10 years
thats about tiem im gonig to buy a new computer
 

Starr

Daemon Poster
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926
spank_fusion said:
Don't worry, AGP isn't dead yet. However, it will be phased out eventually. I'd give it around five to ten years, but that's just a guess.
Sooner then 10 years definantly. I don't give it a very long string. A year maybe two....
 
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