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unused contacts on PCI-E 16x cards?



 
 
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  #1  
Old December 20th 19, 01:23 PM posted to alt.comp.hardware.pc-homebuilt
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Default unused contacts on PCI-E 16x cards?

Cleaning out the junk cupboard, I removed a graphics card from a HP craputer.
It is a fanless 1 GB GT620. I noticed that at least 10% of the edge contacts
are missing. So are there unused contacts (for PCI-E version 4 or whatever) or
is this a crippled card?
  #2  
Old December 20th 19, 04:55 PM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
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Default unused contacts on PCI-E 16x cards?

wrote:
Cleaning out the junk cupboard, I removed a graphics card from a HP craputer.
It is a fanless 1 GB GT620. I noticed that at least 10% of the edge contacts
are missing. So are there unused contacts (for PCI-E version 4 or whatever) or
is this a crippled card?


They can remove the excess ground contacts.

The ground contacts are there to try to maintain some
controlled impedance target level. Typically low amplitude
high speed signals have flyby 100 ohm termination at the end.
The actual terminator today is likely inside the chip on the receiver.

The grounds do a couple things. Shield one part from the adjacent
pair, on crosstalk. And are also part of the impedance (although
a tiny tiny part at that range). If could be that inner layers
have ground we can't see.

http://media.bestofmicro.com/B/D/989...e-slot-big.gif

The practice might have to be reversed when PCI Express Rev.4 cards
come out. Maybe the manufacturers will be "nervous" and put
them back :-) The manufacturers don't all necessarily have
big research facilities to be figuring this stuff out.
(You need a pretty expensive scope to be checking eye diagrams.)

Low amplitude high speed interconnect also tends to
use capacitive coupling. That makes it harder to
exceed common mode DC on the interface, or upset
the biasing on the receiver input pads. And that's how
you check whether a card is "x8 wiring" or not. You
count capacitors, the tiny ceramic caps coupling the
signals. At high frequency, even a small cap has plenty
of coupling (low Xc).

The GT710 is x8 wiring. This product pulls out the stops.
This card uses the shorter x8 connector. It removes the excess
ground contacts. And it has 8 pairs of caps for bus
lanes plus a pair of caps for the clock pair. It's
not a perfect specimen, as there are caps unrelated
to the business end of the thing in that picture.

http://www.palit.com/product/vga/pic...c15fd0008e.png

I could also find GT710 cards with the full x16 connector
and 16 pairs of caps and so on. But the video card
was "off-brand" and presumably this was part of
their marketing drive to snag consumers who thought
the extra window-dressing made a difference. Chopping
off half the wiring on a gutless card like this, makes
no difference at all. It could likely work just as
well with an x4 wiring plan. (Of course the marketing
department would kill the engineer for messing up
their marketing message if that happened. As soon as
consumers see the x4 wiring, they know it's a loser.)

(Example of a GT710 with all sixteen lanes. See picture of back
of card, to "count capacitors".)

https://www.storeeng.com/product/col...b-ddr3-64-bit/

Paul
  #3  
Old December 21st 19, 02:14 AM posted to alt.comp.hardware.pc-homebuilt
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Default unused contacts on PCI-E 16x cards?

On Friday, December 20, 2019 at 11:55:23 PM UTC+8, Paul wrote:

I could also find GT710 cards with the full x16 connector
and 16 pairs of caps and so on. But the video card
was "off-brand" and presumably this was part of
their marketing drive to snag consumers who thought
the extra window-dressing made a difference. Chopping
off half the wiring on a gutless card like this, makes
no difference at all. It could likely work just as
well with an x4 wiring plan. (Of course the marketing
department would kill the engineer for messing up
their marketing message if that happened. As soon as
consumers see the x4 wiring, they know it's a loser.)


Could be for server mainboards that often have a heap of x4 slots for fibre
channel, fast ethernet etc. And you want to put in a graphics card that is
a little bit better than the onboard VGA. Although that would be a pretty
small market. I can't think of an AMD x4 graphics card off the top of my head.
  #4  
Old December 21st 19, 04:49 AM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
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Posts: 2,407
Default unused contacts on PCI-E 16x cards?

On Fri, 20 Dec 2019 17:14:07 -0800 (PST), wrote:

And you want to put in a graphics card that is
a little bit better than the onboard VGA. Although that would be a pretty
small market. I can't think of an AMD x4 graphics card off the top of my head.


Onboard VGA is apt or can mean, besides and at least for AMD, a
separate class of CPUs to run through W10 graphic drivers so
provisioned for the CPU build as AMD's so-called "graphics CPU". A
relative low-end perception given the various Ryzen octal cores
positioned for mainstream value at 3.5-4.5GHz, ranging from $200 to
approaching $100. Higher 16 and 24 cores exceeding $400 CPUs would be
immaterial to $400 for a videoboard and as such and for a specialty MB
to maximize it. A realistic appraisal for little else if not
predominately a sizeable game industry.

Although I'd agree with the principle "little better".

I still don't like the eventuality this present 32" monitor holds, a
monitor replacement for my last 32" that failed. There are several
genuine "32" monitors" edging downwards to $200 for presumably a
serious PC graphical display. Samsung, ASUS, some other models models
I've seen, offhand. Whereas my replacement would seem more along a
"television class" display on a less serious if marginally adequate
note.

That PCI-E board, given a good choice on foremost named performance,
even if value oriented monitor among increasing 32"-class monitor
competitors, may well mean a world of difference in overall clarity
and sharpness to gamma and contrast and perhaps refresh rates. An
application dependency, and though that might not cut it -- the gamer,
the graphics designer, photo renderer -- nonetheless what it does mean
may be the more to the lot, to the HTML website editor and similar,
above all else, in a worldful of no doubt whishy-washy and pinhead
eye-destroying, value conscious, monitors. The Little Better does
indeed get even better.

The first thing to consider might be is a MATROX PCI-nonExpress
videoboard I still do have. Old, for timings contingent to within
standards. Marketed for MATROX's no-nonsense business grade solution,
a consideration over on-board graphics. Even if a PCI-speed
bottleneck, I'd still be curious if there's a better to either my MB's
onboard video, or an addition PCI-E lowend graphics card, I also have,
in what if possible is then up to maximizing or approaching aspects
for these new if hypothetical $200 32" monitors, otherwise in
devaluing dedicated 32" PC, PRO-grade monitors traditionally valued at
$400 and well above that.
 




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