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Sony CPD-G420S Bandwidth

Last response: in Computer Peripherals
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January 16, 2003 12:24:48 AM

I have tried Sony Customer Service, vendors, and sales reps. No one can tell me what the bandwidth is for the Sony CPD-G420S monitor. Does any one know this specification. The reviews on this monitor are positive. But, I won't buy it if I don't know what the bandwidth or pixel clock is for this monitor!
January 16, 2003 4:16:56 PM

The G420S is a 110Khz monitor capable of 1600 x 1200 at 85 Hz, the pixel clock at 1600 x 1200 at 85Hz is 229.5Mhz.

Don’t confuse “Bandwidth” and “pixel clock”, although related they two completely different things.

Bandwidth is a little complicated and needs some explanation and background in monitor technology.

There are three components that make up the monitors refresh rate. Pixel clock, horizontal scan rate, and the vertical scan rate or “refresh rate”. They are all interrelated.

Monitors draw pixels on the screen one at a time starting in the upper left corner across the screen, then down one line and so on. The time it takes to draw one pixel on the screen is commonly called the video rate, pixel clock or bandwidth. The time it takes to draw one line across the screen is the horizontal scan frequency. Finally the time it takes to draw one complete field “entire screen” is the refresh rate.

Basically, the faster you can draw one pixel on the screen, the faster you can draw a line across the screen, the faster you can refresh the screen.

Almost all monitors on the market today have pixel clock and bandwidth specifications that are sufficient for the resolution the manufacturer recommends. But be careful out there. I see some manufacturers that publish the maximum resolution in BOLD print and the recommended resolution is small print. What they are saying is. Yes the monitor will display at that “BOLD FACE RESOLUTION” however the bandwidth of the monitor is really optimized for the lower “recommended” resolution”.

"Bandwidth" is the range of video frequencies that can be adequately handled by the video amplifier of the monitor, this number can be considerably lower than the pixel clock required for a given timing. The reason for this? The highest fundamental frequency in the analog video signal is one-half the pixel clock, since the fastest thing you can do is to turn alternate pixels on and off. One "on" or "white" pixel followed by one "off" or "black" is required for a full cycle - so the highest fundamental frequency you see is derived from the period of TWO pixels, not one.

There are many ways to measure “Bandwidth” - some relevant, and some not. Without knowing how the manufacturer measured the bandwidth it may not be a very useful specification for comparison purposes.

Jim Witkowski
Chief Hardware Engineer
MonitorsDirect.com

<A HREF="http://www.monitorsdirect.com" target="_new">MonitorsDirect.com</A>
January 17, 2003 12:26:03 AM

Thank you for explaning the difference between the pixel clock and bandwidth.

Ultimately, I am trying to determine which monitor has the higher performance between the Sony CPD-G420S and the Iiyama Vision Master Pro 454. The confusing part about the bandwidth specification as in the case of the Iiyama VMP 454 is that the manufacturer lists the spec as: Video Bandwidth - 345MHz dot clock. Bandwidth and Pixel Clock appeared to be used interchangably.

The Iiyama is an 130KHz monitor capable of 1600 x 1200 @ 90 Hz. The video bandwidth is 345 MHz, but the recommended resolution is 1280 x 1024 @ 100 Hz. The Sony CPD-G420S recommended resolution is 1600 x 1200 @ 85 Hz. The question now is which monitor will deliver the best performance at higher resolutions? Going by the recommended resolutions, I would say the Sony. So the higher bandwidth is not a specification that I should give too much weight??

I just ordered an Iiyama Vision Master Pro 454 based on the review found in THG. The overall specifications appeared to be better (higher) for the Iiyama VMP 454 than the Sony CPD-420S. I came close to ordering the Sony. Perhaps I should made a mistake. But I suppose the proof is in the display.

Thanks again.
January 17, 2003 2:56:30 PM

Yes sometimes these two terms are used interchangeably which is very confusing.

The horizontal scan frequency is the key specification to look at. What resolution/refresh rate are you planning on running? Both can do 1600 x 1200 at 85Hz.


Jim Witkowski
Monitorsdirect.com


<A HREF="http://www.monitorsdirect.com" target="_new">MonitorsDirect.com</A>
January 20, 2003 3:19:22 PM

I wasn't sure what the optimal resolution and refresh rates are for video use. I built a system specifically to convert home video to DVD due to the degradation of magnetic media over time.

I am just trying to get the highest performance 19" monitor that won't break my budget. At the same time I want a monitor that displays clear, crisp text also. I realize that I am trying to get the best of both worlds in one monitor. The shadow mask monitor generally displays clearer, crisper text, but the aperture grille type monitors usually have higher resolution and horizontal scan frequencies. For video, I eventually decided on the aperture grille type monitor in the Iiyama or Sony.

I finally received the Iiyama VMP 454. Being my first aperture grille type monitor, I am not sure how the Iiyama compare with other A.G. monitors. It does have a shake to the picture. The moire adjustment helps if I crank up the setting to above 80%. But then the text gets fuzzy. Also the horizontal lines on the left side (left third) of the screen bend upward. The lines are off by a 1/4 inch in relation to the upper damper wire on the far left side of the screen. Are these two things normal for an A. G. type monitor? The packaging was damaged and not original. The monitor was missing the outter box that Iiyamas are shipped in.

I am contemplating returning the monitor. Any advice would be appreciated. Thanks.
January 24, 2003 10:01:41 AM

Hi berndusa,

I'm thinking of getting the iiyama vm pro 454 also. Did you get the new revision of the 454?

The original version (manufacturer code HM903DT) had a lower max. resolution and a dot pitch of 0.25mm at the centre of the screen and 0.27mm at the edges, while the newer version (HM903DTA/HM903UTA) has 0.24mm across the whole screen. See <A HREF="http://forumz.tomshardware.com/ce/modules.php?name=Foru..." target="_new">my post</A> for more info.

I'm not a monitor expert, but in response to the two problems you have noticed:

The picture shake / text fuziness with moire adjustment may be "normal" (not ideal, but within specification). The <A HREF="http://www6.tomshardware.com/display/20020319/index.htm..." target="_new">THG review</A> refers to something like this, as do some of the other reviews on the web (however these all refer to the original (HM903DT) version of the monitor).

The horizontal line distortion does not seem normal however. (Have you tried the geometry adjustment controls?)

I would be concerned about the unoriginal and damaged packaging - it sounds like the monitor may have taken a beating in transit. CRT tubes are relatively sensitive to rough handling.

Rgds,
Ken.
January 24, 2003 10:14:26 PM

mrkH,

I got the new version [HM903UTA] of the Iiyama VMP 454. I don't know if any vendor out there is selling the old version. I bought one from newwegg. I did send the monitor back. They were very cooperative since the box and possibly the monitor was damaged. As I said in a previous post, the Iiyamas are usually double boxed. This one was not.

There isn't much one can do to alter the geometry of horizontal lines, whether the line is "bowed" or off just on one side. All that I could to was rotate the picture a little to minimize the effect in relation to the damper wire.

I attributed the horizontal line being off on the left side to the monitor being "jarred suddenly" or possibly dropped. There was some damage to the inner box. But it wasn't major. The large, bottom strofoarm packing was split in two. For it to split like that seemed to indicate that the box was dropped.

The picture shaking was hard for me to deal with. My wife didn't seem to notice it much, but she only looked at it once and from an angle. The text seemed some what blurry to me, but my wife thought it was okay. I am used to using a shadow mask type monitor where the text is crisp and clear. So I might have been just a little too picky when it came to the text. I have read the many user reviews on the Sony CPD-G420S. Most reviews include a comment on the clear, crisp text of the Sony G420S.

I gave up on the Iiyama. I received two other monitors from two different vendors that had both the inner and outter boxes retaped. Where the these monitors taken out of the box? I rejected shipment of these monitors without opening the inner box. I refuse to accept a monitor that has been opened and repackaged! A third monitor also looked previously opened and retaped. I did open the inner box to find everything opened and repackaged. The inner stryofoam packing was also busted up. These monitors came direct from an Iiyama here in the U.S. I was assured that these monitors are brand new and never used. I had my doubts. At the very least, the boxes (monitors) were handled very poorly. What I describle above is a pattern that was consistent with four Iiyama monitors. Perhaps Iiyama needs to redesign the packaging for these monitors. The Iiyama that I did take out of the box and try was manufactured in November of 2002. I did not check the previous three that came direct from Iiyama. So the monitors being shipped from Newegg are brand new and the new version. These monitors are just bounced around a bit.

I could have lived with the horizontal lines being off on the left side of the screen, but the "picture shake" was to hard for me to cope with. Cranking up the moire control to 80% at the expense of relatively clear text was not worth it for me. Yes, I have seen the expert comments that aperture grille type monitors are very sensitive to being bounced around. That is why I sent it back. The monitor may have been damaged. I don't have the diagnostic equipment or software to make that determination. I'm ordering the Sony as soon as I get done replying to your post.

I hope my long explanation helps.

Berndusa
January 25, 2003 12:29:35 AM

Thanks for the detailed info berndusa.

Looks like the new HM903UTA version may not be any improvement - that "picture shake" sounds quite like some of the symptoms I've seen described in reviews.

Good luck with your Sony.
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