Archived posting to the Leica Users Group, 2017/08/03
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Thanks, Brian. Makes complete sense. On Thu, Aug 3, 2017 at 1:31 PM, Brian Reid <reid at mejac.palo-alto.ca.us> wrote: > There is an electronics/mathematics issue that factors into large > displays. It's why I have an iMac and not an external display. > > At any given time, the computer and electronics industry has some means > that is the fastest for rapidly and reliably moving data over a cable. USB > has never been in contention, but FireWire, Thunderbolt, DVI, and Fibre > Channel have all been candidates for "the fastest and best" at one time or > another. Ethernet, at any speed, has never been the fastest. > > The 5K Retina display has about 15 million pixels. Each pixel can have > about 10,000 different values (this number is a little soft). So one > screen-shot on a 5K Retina display is 150 thousand million bits, about 150 > gigabits. > > So to keep an iMac Retina display happy you have to feed it about 150 > gigabits for each screen refresh. People like 30 or 60 screen refreshes per > second. > > By putting some fast computing inside the display itself you can get away > with not having to send the whole 150 gigabits every time. Which is a good > thing, bdcause 150 gigabits sent 50 times per second is 7500 gigabits per > second. > > If you try to send 7500 gigabits per second over a cable, you run into all > manner of bad-ass electrical engineering issues. When good electrical > engineers are speaking in hushed tones of the expertise of a master, they > sometimes say "she can do terabit connections". > > If you have an external display, then you have to have a cable that > connects your computer to your display. That cable has to have at least one > connector on it, so that it can plug into the computer. (Often the cable is > permanently attached to the display to avoid having to use a connector > there). Connectors are the black beast of high-speed signal transmission. > They are much more difficult to design than cables, and cables themselves > are hard. > > In an iMac, the circuitry that generates the display signal is about 1 > inch away from the screen, and you can make multiple connections if you are > tricky. That way you won't have to send the whole 7.5 terabits per second > over one cable. > > It's much easier to design and build the ultra-high-speed transmission > capability in an all-in-1 design like the iMac than it is to design and > build something that uses, say, an Eizo air traffic control display > connected to a computer 5 feet away. > > This is more or less why an iMac with a killer screen is just a few > thousand dollars, while an air-traffic-control display system with 10 good > screens (though not as good as the iMac) is a few million dollars. > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information > -- Regards, Sonny http://sonc.com/look/ Natchitoches, Louisiana 1714 Oldest Permanent Settlement in the Louisiana Purchase USA