AGP or PCI

[Carlos CZ]

Hi group,

Is there a way to determine,

* If my machine uses the PCI bus controller or the AGP bus controller,
or, perhaps I have ... both?, althougth I think this last condition is
not possible.

* If I have both, could I configure wich one I shall use?

When I see Device Manager, see by conection,
I see PCI, then after it, I see AGP controller before my monitor items,
but, I think, that in principle, only PCI controller cant help any AGP
graphics Card.

Thanks, Carlos

 

[Malke]

Hi group,

Is there a way to determine,

* If my machine uses the PCI bus controller or the AGP bus controller,
or, perhaps I have ... both?, althougth I think this last condition
is
not possible.

* If I have both, could I configure wich one I shall use?

When I see Device Manager, see by conection,
I see PCI, then after it, I see AGP controller before my monitor
items, but, I think, that in principle, only PCI controller cant help
any AGP graphics Card.

All computers have PCI slots. Most computers have an AGP slot (there is
only one) for the graphics card. If you have an AGP controller listed
in Device Manager, then your computer has an AGP slot. What is the
make/model of your video card? It will be listed in Device Manager
under the Display category?

What are you trying to do? I'm afraid I don't understand your last
paragraph.

Malke

 

[Carlos CZ]

Hi Malke,


Well, I suppose, that if I have AGP bus controller, in device manager,
seeing by conection,
I should see "AGP bus" instead of "PCI bus", before many items connected to
this controller,
because I think, this controller sends information to dispositives.

My Device Manager (seeing by conection) looks

PCI bus <--- I think this should read AGP,
if I have AGP bus controller
... conected items
... conected items
Via Tech CPU to AGP controller <---- for me this
is contadiction (*)
S3 Graphics Inc Card Savage 4
Plug and Play Monitor
... connected items
... conected items

(*) is contradiction because an AGP graphics card, should work very fine
only with
an AGP bus controller, and not so much with a PCI bus controller.

Well, I am puzzled for the posibility of changing PCI bus controller, by the
AGP controller, and so
I should read AGP bus.

thanks very much, Carlos.

 

[Mike Hall - MS MVP Windows Shell/User]

Carlos

Read this.. http://webster.cs.ucr.edu/AoA/Windows/HTML/IOa2.html ..

If you are looking at the choice offered in BIOS for PCI or AGP graphics,
you select whichever you know you have.. please note that if you have PCI
selected, but an AGP graphics installed, the AGP graphics will NOT run at
PCI bus speeds.. the BIOS option determines where the system looks FIRST for
a video output device..

 

[Malke]

Carlos

Read this.. http://webster.cs.ucr.edu/AoA/Windows/HTML/IOa2.html ..

If you are looking at the choice offered in BIOS for PCI or AGP
graphics, you select whichever you know you have.. please note that if
you have PCI selected, but an AGP graphics installed, the AGP graphics
will NOT run at PCI bus speeds.. the BIOS option determines where the
system looks FIRST for a video output device..

Thanks Mike. I totally did not get what the OP was trying to do.
Frankly, the easiest way to determine what is inside a computer is to
open it and look.

Malke

 

[Vanguard]

You have an AGP *controller* which bridges to the PCI *bus*. The only
AGP *bus* is between the slot and the controller (which bridges the
secondary and dedicated AGP bus to the PCI bus). It is the yellow
colored bus in the link that Mike gave you. AGP is a port and not a bus
because it connects only 2 devices: the CPU and the video card. The PCI
*bus* has many devices on it (and not all are on daughtercards) so there
is contention. There is no contention for the AGP video card because
the controller (on the PCI bus) is dedicated to only one device (the
video card).

If you have an AGP controller, you *usually* have an AGP slot. You may
not have an AGP slot if you have onboard graphics. Some mobos with
onboard graphics don't provide the option of using an AGP slot (so you
are always stuck with using their onboard graphics). I'd recommend not
getting one of those mobos since you have no hardware upgrade path.

Have a read at http://www.pcguide.com/ref/mbsys/buses/types/agp.htm.

 

[Carlos CZ]

Thanks very much to all of you for your good answers, I am analiyizing your
comments

Carlos

 

[Mike Hall - MS MVP Windows Shell/User]

and when they do that, they get pissed because there is not much in there to
show for the money paid out.. lol

 

[Carlos CZ]

Hi all again,

Finally I finded the root of my contradictions,
what happened is that my book only show two posibilities:

* or you use a PCI bus controller,
* or an AGP bus controller that replaces completelly the
PCI controller, yes, there is no PCI here.

actually, I believe my motherboard uses a scheme like the one showed
in picture 7.7 of the Mike's link, wich is clearly a different approach, and
seems to isolate the AGP mechanism to the video system, leaving the rest
connections to PCI ( I wonder why to keep PCI, but this is secondary item ),
but well, I need some time to understand and verify things related.

thanks and have a nice day, Carlos.

 

[Mike Hall - MS MVP Windows Shell/User]

Carlos

You have the option of either using a PCI (not to be confused with the more
recent PCI-e) or AGP video card, hence the options.. AGP controls video only
where the PCI relates to whatever is inserted into a PCI slot..

 

[paulmd]

Hi all again,

Finally I finded the root of my contradictions,
what happened is that my book only show two posibilities:

* or you use a PCI bus controller,
* or an AGP bus controller that replaces completelly the
PCI controller, yes, there is no PCI here.

If this is in an actual textbook, someone needs to have a chat with the
author.

Most machines have an AGP slot, but there's no requirement for one. Or
at least one PCI slot, which is also not a requirement, or the newest
ones have PCIe, and your old 286s and 386s will have an ISA video card.
Yet another option is having the video integrated into the motherboard.
And old macs used nubus, so this discription given is woefully
incomplete.

actually, I believe my motherboard uses a scheme like the one showed
in picture 7.7 of the Mike's link, wich is clearly a different approach, and
seems to isolate the AGP mechanism to the video system, leaving the rest
connections to PCI ( I wonder why to keep PCI, but this is secondary item ),

Because PCI is useful for other kinds of cards, audio, ethernet, modem
and so on.

 

[Carlos CZ]

Hi Paul

No, my book isnt actual, its a book I bougth more or less in 2000 year,
perhaps my real fault is to read my book wich is from that year.

But the essential point, are not the AGP or PCI slots, those are very easy
to understand, but the fact that the PCI controller could to be completelly
replaced
by an AGP one. Further, this AGP is called "the Set AGP", and it connects
this way

Pentium,
//
Phisical memory = Set AGP = ISA controller
// //
Slots Slots

as you see, no PCI. and there is a big difference, because data to the
physical memory directly. For this, it dont goes to Pentium first. this is
why I wonder, why to keep AGP
reduced only to video system ?, but I shall think on that later.

thanks, Carlos.

 

[Carlos CZ]

A little important point

really, I "understand" that AGP gives a faster DMA than PCI,
sorry, I am not experienced on this things.

Carlos

 

[Mike Hall - MS MVP Windows Shell/User]

Carlos

The PCI bus CAN NOT BE REPLACED BY THE AGP BUS.. the AGP bus is GRAPHICS
ONLY..

AGP is an acronym for ACCELERATED GRAPHICS PORT

 

[Carlos CZ]

Hi Mike, yes, I supossed it is, but, my book dont shows PCI,
well, a point is that I am showing what is presented in the book,
I not saying I am rigth with my comments, as I am saying,
I am starting to understand. Too, we must be care, sometimes
there are languages abuses. Perhaps author was true but not today.

Carlos.

 

[Carlos CZ]

Further, I am not saying AGP bus, but AGP bus controller, as in the figure.
Of course, the bus should must be the same, no need to call it PCI or AGP.

Carlos

 

[Mike Hall - MS MVP Windows Shell/User]

Carlos

Look at the diagram 7.7 in the article I sent to you.. the bus coming from
the CPU splits into the PCI bus and AGP bus via PCI and AGP controller
respectively.. they are not one and the same, hence the different names..

 

[Carlos CZ]

Hi Mike,
I am not saying that the picture on my book is similar or equivalent to fig
7.7,
but that both are different schemes. If you doubt of what I say, this is my
book:

Informatica Total, 1999, White and Defler
capitulo V., pag 121.

Later I shall send an scanned copy of the page.
My book says it is a translated book, so I suppose there is an english
version of it.
Please, I am starting with this, so, dont claim me for things I have no
responsability.

Carlos

 

[Carlos CZ]

Excuseme, I am tired, White & Derfler, Part V, Chapter 18, page 121 is
correct.
but dont worry, I shall send the picture. PCI and the other AGP arrangment.

Carlos.

 

[cquirke (MVP Windows shell/user)]

Carlos CZ wrote:

That's completely inaccurate.

AGP is not a bus, in the sense that it supports multiple devices; it
is for one display controller only. It was developed soon after the
Pentium II was released as a way to relieve the display controller of
the bottleneck posed by PCI's 33MHz-by-32-bits standard.

AGP did the following to do that:
- increased clock speed to 66MHz
- transfer 2 bits per every clock cycle for 133MHz
- allowed fast access to system RAM for 3D textures etc.

Later revisions of AGP increased the number of bits per clock pulse
(while the clock stayed at 66MHz) and dropped the operating voltage to
facilitate this. That's why you can't mix old AGP motherboards with
new AGP cards and vice versa, if the voltages don't match!

An AGP-era motherboard always has PCI as well as the single AGP.
There may be onboard graphics that are internally AGP, an AGP slot, or
both - but when both are present, only one works at a time.

AGP has now been superceded by PCI Express, which offers a more
flexible way of combining units of bus throughput to taste. So far,
PCI Express motherboards come with legacy PCI slots, new PCI Express
slots using 1 bandwidth unit each, and a single 16-unit PCI Express
slot for the display controller where the AGP slot used to be.

You don't get AGP and PCI Express on the same motherboard.

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