In article <(E-Mail Removed)>,
(E-Mail Removed) wrote:
> Hi
>
> In the manual it is written: "This Accelerated Graphics Port (AGP) slot
> only supports 1.5V AGP 8x mode graphics cards".
>
> Do you think "only" restricts the tension (1.5V) or both the tension
> and the pace of the port (8x)?
>
> I want to install a GeForce 4 Ti4200 on a A7N8X-X
> - It is OK concerning the tension (there are 3 notches in the golden
> fingers of the card, as shown in the manual)
> - But the card is an AGP 4x card. Is not AGP8x supposed to be
> compatible with previous version of AGP (at least 4x would be enough),
> like USB 2 ports accept USB 1.2...
>
> Has anyone already tried to install a GF4 4200 on a A7N8X-X ?
>
> Thanks,
> Pierre
From an end user perspective, this article explains it.
There shouldn't be a problem using a 4200. This article
has a simplified classification table, and lists of
video cards and motherboards, for easy matching.
http://www.playtool.com/pages/agpcompat/agp.html
The following section is a weak attempt at an explanation:
*******
There are two _supply voltages_. 3.3, 1.5
There are three _signal voltage_. 3.3, 1.5, 0.8
There is one signal on the AGP slot, that distinguishes
the supply voltages. TYPEDET states whether the video
card prefers 3.3V or 1.5V.
A supply voltage is what powers a chip and its I/O drivers.
A signal voltage is the height of the wiggly signal that
extends between chips. They do not have to be the same
numeric value, to work.
3.3 supply 3.3V signal 3.3 supply
| | |
|\| | |\|
| \ v | \
TX ___| \__ resistor __________________| \___ RX
| / | /
| / | /
|/| |/|
| |
GND GND
1.5 supply 1.5V signal 1.5 supply
| | |
|\| | |\|
| \ v | \
TX ___| \__ resistor __________________| \___ RX
| / | /
| / | /
|/| |/|
| |
GND GND
1.5 supply 0.8V signal 1.5 supply
| | |
|\| | |\|
| \ v | \
TX ___| \__ resistor _________+________| \___ RX
| / | | /
| / termination | /
|/| resistor |/|
| | |
GND GND GND
My interpretation of the standard, is when the 0.8V signal
amplitude is used, there is a termination resistor inside
the receiving chip, that is engaged. The voltage divider
action, between the sending resistor and the termination
resistor, reduces the voltage, and that is where the 0.8V
amplitude signal comes from. (My drawing of the resistors
above, is means to illustrate the concept of attenuation,
and is not meant to be taken literally.)
So, the middle figure is AGP4X compatible, the lower figure
is AGP8X compatible. The video card GPU cannot be destroyed,
because the _supply_ voltage in each case is 1.5V. The signal
amplitude could be misinterpreted, if for some reason the
two ends of the interconnect don't agree on which standard
they are using, but there are two other signals on the AGP
slot connector to sort that out. (On the playtools web page
quoted above, the miscommunication cases are the yellow
squares in one of the tables. In the real world, no "yellow
square" combinations exist, and that is why it is possible
to construct the simplified table below it.)
As a result, from a damage perspective, a 4X and 8X should at
least fit in the same AGP connector (keyed for 1.5V), and should
not be damaged by the experience. Since I cannot find any
documentation describing the implementation of the triangles
in the above drawings, I cannot explain it further than that.
Paul
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