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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Wed Nov 27, 2013 3:31 pm Post subject: (non professional) VGA card bandwidth evaluation |
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Here we are, I started a small campaign to evluate the common VGA card's output performance, there are a lot of parameters that should be considered, but for now I focus only on the rise time measurement giving a clue about the bandwidth of the actual card, if there is interest in this thread the measured parameters could be extended later of course.
The measuring theory and method
This is not a reference level measurement, but later when the number of the measured cards are growing they could give a good basis of comparision.
The best way would be to get an oscilloscope with bandwith of at least 500MHz, but that's not a cheap toy for fun experiments. So I choose the indirect way of measurement.
I have an old HP 1720A analog oscilloscope, originally it was a military item, used by the USAF, after that it still remained in the corporate sector until I bought it from a friend who bought it at their rollout. It has an advertised bandwidth of 275Mhz, has switchable 50 Ohm input, it was held in good hands, but the last calibration date is unknown, otherwise it seems to be accurate enough for hobby purposes.
The VGA cards are connected directly to the scope's BNC input with a 3m (10 feet) long, VGA-BNC cable Fujikura brand. Though the standard VGA output would require a 75 Ohm termination I used the scope's 50 Ohm internal termination, but that does not affecting the rise time of the circuit. I did this to measure with the least intervention to the original signal and to ease the measurement.
A system's bandwith is proportional to its rise time and vice versa, the used method is based on the theory of rise time of cascaded blocks, in a perfect world this would mean if I would connect an infinitely fast rising edged signal to my oscilloscope I would measure 1,27ns rise time (=0,35/275MHz, see above the wiki link).
An other example: If I connect a (flat to) 400MHz (->tr=0,87ns) VGA card to my (ideal) scope (->tr=1,27ns) that would mean an 1,54ns overall rise time, and this is actually observable on my oscilloscope since it has a 1ns/div speed, that is further divided to 5 subdivisions.
For the further calculations I difine that my scope's rise time is 1,3ns, wether it is really or not, but until the measuring rig remain the same all myl measurements will be comparable.
_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Wed Nov 27, 2013 3:44 pm Post subject: |
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Asus nVidia GeForce 7950GT 512MB (PCIe):
Measured in 800x600 with a specially breed test pattern (to ease scope triggering) otherwise this is a simple multiburst, bandwidth pattern.
There was a slight overshoot, I set the 100% level to where the signal settled,
Total measured rise time(10%-90%): slightly less than 1,6ns
solving the equation gives us: 0,93ns calculated rise time for this card which would mean a bandwidth of about 375MHz, where the advertised bandwidth is 400MHz.
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nVidia GeForce 7950GT rise time on a HP1720A o'scope |
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_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
Last edited by gjaky on Wed Dec 04, 2013 12:31 pm; edited 1 time in total
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Wed Nov 27, 2013 3:54 pm Post subject: |
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integrated intel GMA950 (i945GZ on a foxconn motherboard):
Measured in 1920x1080 96Hz with the same pattern as above
Total measured rise time: 2,4ns
Calculated rise time for this VGA: 1,77ns -> ~200MHz, this is about the half of the advertised 400MHz.
That's it for now, an ATI HD3650, and other nVidia cards will follow soon.
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intel GMA950 integrated VGA rise time on a HP1720A o'scope |
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23043 Time(s) |
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_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
Last edited by gjaky on Wed Dec 04, 2013 12:31 pm; edited 1 time in total
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AnalogRocks Forum Moderator
Joined: 08 Mar 2006 Posts: 26690 Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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Link Posted: Wed Nov 27, 2013 5:26 pm Post subject: |
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I'll be interested to see the ATi 3650, I think that's what is in my HTPC
_________________ Tech support for nothing
CRT.
HD done right!
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fragzero
Joined: 30 Aug 2012 Posts: 344
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Link Posted: Wed Nov 27, 2013 5:34 pm Post subject: |
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It might be a good idea to photograph the card, not every manufacturer uses the reference design!
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Wed Nov 27, 2013 5:56 pm Post subject: |
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fragzero wrote: | It might be a good idea to photograph the card, not every manufacturer uses the reference design! |
Of course that can be done, the above mentioned asus card is a reference design, asus didn't even bothered to remove the original nvidia sticker from the heatsink, they just put their sticker on it
In the meantime I figured out maybe I can test a HDF1 soon too..
_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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winny
Joined: 09 Oct 2013 Posts: 403 Location: Sweden
TV/Projector: BD808s, BG1209/2
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Link Posted: Wed Nov 27, 2013 8:22 pm Post subject: Re: (non professional) VGA card bandwidth evaluation |
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gjaky wrote: | The best way would be to get an oscilloscope with bandwith of at least 500MHz |
I have a 500 MHz DPO4000 at work and if you send me the test pattern, I'll gladly measure whatever card I have laying around for you. Someone with a GHz scope should be better though.
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Wed Nov 27, 2013 9:23 pm Post subject: Re: (non professional) VGA card bandwidth evaluation |
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winny wrote: | gjaky wrote: | The best way would be to get an oscilloscope with bandwith of at least 500MHz |
I have a 500 MHz DPO4000 at work and if you send me the test pattern, I'll gladly measure whatever card I have laying around for you. Someone with a GHz scope should be better though. |
Sure! See the attached picture bellow, I used this at full screen in 800x600, that's about enough as we are only interested in the steepness of the rising edge.
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22998 Time(s) |
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_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Wed Dec 04, 2013 12:29 pm Post subject: |
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Reference (Sapphire) ATI Radeon HD4650 (PCIe):
Measured at 640x480
Measured rise time: 1,8ns
Calculated rise time for VGA: 1,2ns -> ~280MHz (claimed bw: 400MHz)
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22929 Time(s) |
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_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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fragzero
Joined: 30 Aug 2012 Posts: 344
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Link Posted: Wed Dec 04, 2013 1:54 pm Post subject: |
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Any chance you can test a HD6350 reference design?
Quote: | http://tiptop.lt/blog/wp-content/uploads/2010/09/amd_radeon_hd_6350.jpg |
Very popular HTPC card last generation!
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Wed Dec 04, 2013 2:25 pm Post subject: |
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fragzero wrote: | Any chance you can test a HD6350 reference design?
Quote: | http://tiptop.lt/blog/wp-content/uploads/2010/09/amd_radeon_hd_6350.jpg |
Very popular HTPC card last generation! |
Unfortunately, I don't have a source to borrow that card, yet.
But I have an nvidia GF6600 and GF8800 card on my list, so we'll see at least how are the generations realated to one another with the nvidia cards... Otherwise I doubt the manufacturers took much effort to make the DACs even better and better with the ongoing generations, it's like wasted wasted time for the mass market... It would be also interesting if a very recent card has any cuttings in the analog performance compared to older cards?
_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Fri Dec 13, 2013 10:01 pm Post subject: |
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ASUS GeForce 8800GTS 320Mb (G80 core, PCIe):
Measured at 800x600
Measured rise time: ~1,7ns
Calculated rise time for VGA: 1,1ns -> ~320MHz (claimed bw: 400MHz) But note the output is very similar to the GF7950GT's only with less overshoot, thus the slightly worse rise time.
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_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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CasetheCorvetteman
Joined: 09 Nov 2008 Posts: 6319 Location: Australia
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Link Posted: Sat Dec 14, 2013 2:18 am Post subject: |
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What do you get from a GigaByte 760 GTX OC Edition?
_________________ Barco CineMAX, 120" OZ Theatre Majestic 16:9 screen, H/K AVR 7.1...
RUNCO DTV991 LC ( NEC XG 852 LC ) 100" 4:3 screen, H/K AVR 5.1...
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Sat Dec 14, 2013 10:00 am Post subject: |
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CasetheCorvetteman wrote: | What do you get from a GigaByte 760 GTX OC Edition? |
Nothing, yet...
_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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CasetheCorvetteman
Joined: 09 Nov 2008 Posts: 6319 Location: Australia
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Link Posted: Sat Dec 14, 2013 10:56 am Post subject: |
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Thats what i have in my main rig, 650Ti in the other.
Both allow me to select Generic CRT for 3D even over HDMI.
_________________ Barco CineMAX, 120" OZ Theatre Majestic 16:9 screen, H/K AVR 7.1...
RUNCO DTV991 LC ( NEC XG 852 LC ) 100" 4:3 screen, H/K AVR 5.1...
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Sat Dec 14, 2013 12:43 pm Post subject: |
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The "latest" nVidia card that I can borrow is a GT240, which is pretty old as well
_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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CasetheCorvetteman
Joined: 09 Nov 2008 Posts: 6319 Location: Australia
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Link Posted: Sat Dec 14, 2013 2:28 pm Post subject: |
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Yeah thats WAY down the order from what i have here...
_________________ Barco CineMAX, 120" OZ Theatre Majestic 16:9 screen, H/K AVR 7.1...
RUNCO DTV991 LC ( NEC XG 852 LC ) 100" 4:3 screen, H/K AVR 5.1...
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noos@xp37+
Joined: 17 Jun 2008 Posts: 464 Location: Berlin/Munich
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Link Posted: Sat Dec 14, 2013 6:01 pm Post subject: |
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I use a 280gtx, and I have one for SLI/spare lying around here. With the next parcel to HU I will include it for you. Great work Gabor!
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CasetheCorvetteman
Joined: 09 Nov 2008 Posts: 6319 Location: Australia
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Link Posted: Sun Dec 15, 2013 12:01 pm Post subject: |
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I have the HDMI output connected to the AVR for audio, the RGB to the projector, then the DVI goes to my 27" monitor.
_________________ Barco CineMAX, 120" OZ Theatre Majestic 16:9 screen, H/K AVR 7.1...
RUNCO DTV991 LC ( NEC XG 852 LC ) 100" 4:3 screen, H/K AVR 5.1...
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gjaky
Joined: 05 Jun 2010 Posts: 2790 Location: Budapest, Hungary
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Link Posted: Sun Feb 21, 2016 7:20 pm Post subject: |
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A new approach, multiburst signal.
Just because I was at it...
nVidia Geforce 6600GT
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_________________ projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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