PCI vs AGP 4

[hchman]

What is the difference between a PCI card and an AGP card? Are the slots different?

Thanks

 

[Comtech]

Yup, slots are different, and AGP runs at it's own speed (1x, 2x, or 4x the bus speed), whereas PCI bus runs at clock speed / 3 (for a 100mhz bus CPU) or clock / 2 (for a 66mhz CPU), or clock / 4 (for a 133mhz CPU).

I think I got that right (blonde moment). X-) Cheers,
Jim

http://members.cnx.net/reboot/

 

[hchman]

You think you have a blonde moment listen to this. What is the difference in the slots and do all PCs have both?

Thanks again. s-)

 

[Comtech]

AGP slot is in a different place, and has a different number of connectors than PCI.
Not all motherboards have AGP (most newer ones do).
Older boards will (may) not, and some proprietary systems do not (Compaq, PB, HP, Emachine...). Cheers,
Jim

http://members.cnx.net/reboot/

 

[butchrecon]

AGP is much faster than PCI. The bandwidth for AGP is:
1X=254.3 MB/s
2X=508.6 MB/s
4X=1,017 MB/s
To a contrast of only 127.2 MB/s for PCI.
Also AGP has the advantage of pipelining. One performance enhancing benefit of AGP is its ability to pipeline requests for data. Pipelining was first used by modern processors as a way to improve performance by letting the sequential parts of tasks overlap. With AGP, the video chipset can use a similar technique when requesting information from memory, which improves performance.

AGP can have access to system memory for better 3D results. Unfortunatly with the large amounts of RAM on video cards makes this obsolete.

Hope this helps.

James Collins
Computer Hardware Engineer
A+, MCP

email: butchrecon@skyenet.net

Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.

 

[CitrixEngineer]

Here's a little more info


(cribbed from webopedia)

PCI

Acronym for Peripheral Component Interconnect, a local bus standard developed by Intel Corporation. Most modern PCs include a PCI bus in addition to a more general ISA expansion bus.

PCI is a 64-bit bus, though it is usually implemented as a 32-bit bus. It can run at clock speeds of 33 or 66 MHz. At 32 bits and 33 MHz, it yields a throughput rate of 133 MBps.


Note that PCI is a generic bus for many types of device controller.


AGP

Short for Accelerated Graphics Port, an interface specification developed by Intel Corporation. AGP is based on PCI, but is designed especially for the throughput demands of 3-D graphics.

Rather than using the PCI bus for graphics data, AGP introduces a dedicated point-to-point channel so that the graphics controller can directly access main memory. The AGP channel is 32 bits wide and runs at 66 MHz. This translates into a total bandwidth of 266 MBps, as opposed to the PCI bandwidth of 133 MBps.

AGP also supports two optional faster modes, with throughputs of 533 MBps and 1.07 GBps. In addition, AGP allows 3-D textures to be stored in main memory rather than video memory.

AGP has a couple of important system requirements:

The chipset must support AGP.
The motherboard must be equipped with an AGP bus slot or must have an integrated AGP graphics system.

AGP-enabled computers and graphics accelerators hit the market in August, 1997. However, there are several different levels of AGP compliance. The following features are considered optional:

Texturing: Also called Direct Memory Execute mode, allows textures to be stored in main memory.

Throughput: Various levels of throughput are offered: 1X is 266 MBps, 2X is 533 MBps; and 4X provides 1.07 GBps.

Sideband Addressing: Speeds up data transfers by sending command instructions in a separate, parallel channel.

Pipelining: Enables the graphics card to send several instructions together instead of sending one at a time.


Interesting point to note is that PCI is ostensibly a 64-bit bus, while AGP is only 32-bit.


butchrecon

I don't think it's unfortunate that newer AGP cards have a large amount of memory on them - on the contrary - I think it's good that useless on-board AGP controllers aren't stealing system memory from programs or the o/s. ;-)

 

[basweek]

What does the "fast writes" option with some newer AGP motherboards do?

 

[butchrecon]

Sorry Citrixengineer I did not mena unfortunatly. (I dont proofread my typing) I was trying to put down fortunatly. Thanks for poining that out. Where did you get your AGP MB/s numbers? they are slightly faster than everything I have seen. James Collins
Computer Hardware Engineer
A+, MCP

email: butchrecon@skyenet.net

Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.

 

[CitrixEngineer]

butchrecon

I guessed that was what you meant - hence the winking emoticon. Just my occasionally very evil sense of humour!

The actual figure is hard to pin down;

Here's one definitive source;

http://developer.intel.com/technology/agp/index.htm

Notice that the figure here is 528MB/sec.

Here's the whitepaper;

http://www.intel.com/technology/agp/agp_index.htm

Note that this document merely specifies "in excess of 500MB/sec" for AGP2, and "up to 1GB/sec" for AGP4.

The 533MB/sec figure is quoted here (another "definitive" source)

http://developer.intel.com/technology/agp/tutorial/chapt_3.htm

Makes you wonder, really...

CE

 

[JohnS9051]

Q. Which figures are correct?
A. It goes back to that old question and argument of "What is a MB?"
If you consider 1MB = 1,000,000 bytes than CitrixEngineer's figures are correct. If you consider 1MB = 1,048,576 bytes than butchrecon's figures are correct.
The debate goes on.
John

 

[CitrixEngineer]

Not my figures, John - Intel's!

They should know, they developed the standard ;-)

Your point is totally valid; As all computer engineers know, 1k = 1024 bytes...

One set of Intel's figures came from 132 (the speed in Mhz of the PCI bus) x 2 for AGP 1 and so on.

The debate does indeed continue...

 

[Ma3x323]

I want somebody with a figure of 24-34-24 ;-);-)

 

[paparazi]

What you all like you technobods.
All the boy wanted to know was which was better and you had to go and try and out do eachother, like a load of showy peacocks!
Modern boards usually have both types of slots
AGP is Brown in colour and there is only one of them
PCI is white and there are always several of them on newer boards (up to six if you're lucky)
ISA is Black (I only mention this so you know if you have one)
Obviously get the AGP graphics card if you have the option
Make sure your motherboard and new graphics card support 2x and 4x AGP to take advantage of the faster interface.

 

[butchrecon]

Whoah buddy! (paparazi)

What is all that about? This and all forums are not about outdoing one another. They are about information. That's it. Trying to out do someone else is ridicules. Everyone has their own opinion and knowledge base that they receive from experience and knowledge. So everyone's answer will vary from tech to tech. That's why someone else's answer may be different. It looks like you have a lot to learn about the tech community. Each person adds a bit more info to the pool. your answer is basic, yes. And no one else stated it. So good job. Just don't scrutinize everyone.
If I am off base here let me know and for that I apologize. Your reply has a feel of crappiness towards the others. James Collins
Systems Support Engineer
A+, MCP

email: butchrecon@skyenet.net

Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.

 

[hchman]

Butchrecon. You are right about the forums. I did not respond because I was getting all of the information I could. Thank you all.

 

[butchrecon]

Its no problem. Thats what we are here for. James Collins
Systems Support Engineer
A+, MCP

email: butchrecon@skyenet.net

Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.