Using iMac As Monitor Requires Very Specific Cable
1:25 am, November 2nd, 2009, Leander Kahney
To use the new 27-inch iMac as an external monitor requires a very specific cable to work: a Mini DisplayPort to Mini DisplayPort cable, to be exact.
It does not work with a HDMI cable or a DVI cable, even when they are strung between a pair of Apple-branded Mini DisplayPort adapters.
There seems to be a lot of confusion about the issue on the web and even at Apple’s retail stores.
The staff at the main San Francisco Apple store were confused about the cables needed to use the iMac as an external monitor for a compatible MacBook Pro. The iMac works only with devices that output video through DisplayPort, which the MacBook does.
To use the new iMac as a monitor, it must enter “target display mode,” which appears to happen automatically when the correct DisplayPort cable is plugged in.
There appears to be only one cable on the market capable of connecting compatible devices to the new iMac: Belkin’s Mini DisplayPort to Mini DisplayPort cable, which is available from Apple’s retail stores for $29.99.
The store didn’t have any in stock, so the staff happily sold me a pair of Mini DisplayPort to DVI Adapters ($29 a pop) — and told me to string them together with a standard DVI cable.
I had to go to another store to find a DVI cable to connect them (another $20). At this store, I found a pair of DisplayPort to HDMI dongles, so I picked them up (another $15 each) and a $12 HDMI cable to connect them.
Neither of these MacGyver solutions worked.
I’ll try to pick up one of the Belkin cables tomorrow and will post the results here.
I tried to use a new 27-inch iMac as an external display for a compatible MacBook. I connected them with a HDMI cable connected to two Mini DisplayPort to HDMI adapters. It didn't work.
Neither would a DVI cable strung between two Mini DisplayPort to DVI Adapters.
Posted by Leander Kahney in Apple, MacBook Pro, News, iMac | Comment on this article
The downside of Apple secrecy.
A product comes out and the staff haven’t been able to kick the tires and learn how it really works.
MacRat, on November 2nd, 2009 at 2:09 am
I hope this isn’t a stupid question
Is it possible to take a external blu-ray player/burner drive and hook it up to the new 27″ monitor and rip a movie to the system or is that also out of the question?
Is it even possible to watch a movie through a blu-ray drive on the new 27″ system via the external hard drive?
Porkchop1234, on November 2nd, 2009 at 2:18 am
In those bottom two pics your lovely new iMac appears to be precariously balanced on the edge of the table. Scary stuff.
jakejake123, on November 2nd, 2009 at 4:09 am
In answer to question one, no. It would appear the video signal is bypassing the iMac’s CPU entirely and just goes straight to the monitor, so ripping from that input would not be possible without serious hackage.
In answer to question two, it would appear from Leander’s testing that the ONLY video input the 27″ can receive is from another Mini DisplayPort, so if you had a PC laptop with a Blu-Ray player, the iMac is still not the external monitor for you.
ChuckEye, on November 2nd, 2009 at 9:49 am
You might want to try one of these and let us all know how it works.
http://www.atlona.com/Atlona-DVI-to-Mini-DisplayPort-Converter-p-17859.html
John Gebhardt, on November 2nd, 2009 at 12:21 pm
Yeah, I researched this when the new iMacs were first announced and found that Atlona converter. I believe Belkin also makes one as well. Both were at least $200. I am trying to connect an older MacBook that only has miniDVI out.
I concluded that I could get an external 24″ monitor with DVI and HDMI inputs for the cost of the $200 converter, so it wasn’t worth it for me.
What I really want is an iMac and then a second display that looks exactly like the iMac. The best solution I’ve found is having two computers and using Teleport.
http://abyssoft.com/software/teleport/
mattmattmatt, on November 2nd, 2009 at 1:36 pm
Is there any way that iMac could be used as an monitor for a PS3 ?
I should buy the new iMac soon,and i dont know should i buy a ps3 with it or not
Kolja, on November 2nd, 2009 at 3:30 pm
1. But I read somewhere (Apple website?) we could attach an external Video Source (BR, DVD Player, etc) with what cable configuration is this possible?
2. And how about the other way around … having a 2nd screen attached to the iMac 27”? normal Mini-Displayport / DVI or Mini-Displayport / HDMI will do?
or there’s a secret as well ?
Bruno Alexandre, on November 2nd, 2009 at 4:00 pm
I’m so sorry… I’m so rude!
Thank you for the wonderful images
I’m in love with the iMac 27” and here is where I stand up minutes and minutes looking to all the rendered pixel of your pictures Leander 
Thanks a bunch !
Bruno Alexandre, on November 2nd, 2009 at 4:02 pm
Use this one:
http://store.apple.com/us/product/TX706VC/A?fnode=MTY1NDA3Ng&mco=MTMzODYwNzk&p=2&s=topSellers
Segenthaler Warefield, on November 2nd, 2009 at 4:38 pm
Use this one:
http://store.apple.com/us/product/TX706VC/A?fnode=MTY1NDA3Ng&mco=MTMzODYwNzk&p=2&s=topSellers
It is $29.95 and supports for resolution from any Mini DisplayPort capable Mac.
Segenthaler Warefield, on November 2nd, 2009 at 4:39 pm
The reason why the adapters won’t work is because mini display port technology is packet based. Other connector types (such as DVI, HDMI, VGA, etc) all transmit images in lines.
Previous macs with Mini Display ports have worked with adapters because they internal video had the ability to also transmit out in the older line-based transmission – essentially the mini display port just became a carrier for an entirely different type of signal.
The new macs no longer have this capability. The only way it can be performed is with much pricier converter boxes, which can be had for 200$-400$.
Mini display port technology definitely has some advantages, however. Because it is packet based you are able to daisy chain multiple displays without regard to the video card’s capability, where as with previous technologies this is not possible.
Apple is just way ahead of the industry curve.
ZacPro, on November 2nd, 2009 at 5:01 pm
Thats to bad that you can’t hook up a blu ray drive to the new Mac. I’m sure if you did the ripping on some low end PC there’s a way you could get the data onto the mac though. Just got to be creative.
Porkchop1234, on November 3rd, 2009 at 3:53 am
I use a KVM switch with as many as four computers, and our top-end computer is due for an upgrade. Apple gave me hope with its limited ability to render video from other machines on the beautiful iMac screen, but to shut out older video streams (vga, dvi, etc.) is a deal-breaker.
As much as I’d love that iMac, I can’t justify having two screens on my desk. Unless this gets fixed, it’ll have to be a Mini and a third-party flat-screen monitor.
ObbieZ, on November 3rd, 2009 at 1:19 pm
The reason the adapters don’t work is that they aren’t bidirectional. It’s not about packet-based tech or anything else (sorry ZacPro!). You can go out, just not in. The cables work, because with cables having the same ends, they are inherently bidirectional.
Byran Newell, on November 3rd, 2009 at 7:44 pm
If I hook a MacBook Pro to the iMac 27 inch and use it as a monitor only, is the iMac smart enough to power down its internal computer parts, saving energy and just use my MacBook Pro as the CPU?
I asked this very question to several employees at the Apple stores and I got several blank looks.
Juan, on November 4th, 2009 at 11:40 am
Forgive me if I am being stupid but I read that if you connect the iMac and the Macbook with a firewire cable, start the Macbook in target mode and then start the iMac whilst holding down the alt key you can use the iMac as a monitor for the Macbook.
Ben Moon, on November 5th, 2009 at 7:37 am