Promise Pegasus R6 & Mac Thunderbolt Review
by Anand Lal Shimpi on July 8, 2011 2:01 AM ESTDisplayPort Passthrough
The Pegasus has two Thunderbolt ports. You can use the second port to daisy chain up to six Pegasus devices together, for up to 36 drives. With a single Pegasus in its default configuration able to hit over 5Gbps, you'd definitely run into bandwidth limitations with six of these things. But you could get by with two and not be limited by Thunderbolt.
There's another role that second Thunderbolt port can play: as a DisplayPort output. Remember both PCIe and DisplayPort are carried on a single Thunderbolt cable, the latter occupying half of the 40Gbps of total bandwidth available.
At the end of a Thunderbolt chain you can insert a miniDP display, currently the only option is the 27-inch LED Cinema Display but in theory other panels that accept a miniDP input could work as well.
I connected a 27-inch Cinema Display through the Pegasus without any problems. The Pegasus does have to be on for you to get video however, so if you ever have to shut down the Pegasus you do lose video to the Cinema Display.
Audio still works, so you'll see the Cinema Display as an audio device on your Mac:
The experience is pretty seamless overall.
I ran a quick test to see if I lost any bandwidth to the Pegasus with the 27-inch Cinema Display in the chain. I measured a slight performance drop (< 3%) in the best case scenario of four SF-2281 SSDs in a RAID-0 array on the Pegasus, but nothing substantial at all. Note that simply displaying an image at 60Hz on the 27-inch Cinema Display requires over 6.75Gbps of bandwidth (because of 8b/10b encoding), so a full Thunderbolt channel is necessary for DisplayPort (although admittedly it only needs to be unidirectional bandwidth).
| Thunderbolt PCIe + DP Bandwidth Test | ||||
| 2MB Sequential Write, QD16 | No DisplayPort Passthrough | 27-inch Cinema Display Connected | ||
| Promise Pegasus R6 (4 x SF-2281 SSDs, RAID-0) | 1002.7 MB/s | 988.2 MB/s | ||
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darwinosx - Friday, July 8, 2011 - link
Hardly anyone uses projectors so VGA ports should only be on business class laptops.Zok - Friday, July 8, 2011 - link
Can't say I agree with you there. Despite being issued a corporate laptop, I use my personal one for most of my work, including (VGA-requisite) projector presenting.cacca - Friday, July 8, 2011 - link
some questions:Does USB 3 port do the same?
Does the PCI-E external do the same?
Does External SATA do the same?
Thunderbolt is just another PROPRIETARY standard that competes with others.
It reminds me RAMBUS.
were cost and compatibility matters. Is faster but....
We will ever seen a review of something from Intel that points out the shortcomings?
or this place is ADDtech instead of anandtech?
André - Friday, July 8, 2011 - link
Rest assured that USB 3.0 does NOT in any way or form do the same as Thunderbolt.The protocols are very different, as in, USB 3.0 nearly doesn't support any and Thunderbolt being an extension of a 4 x PCI-Express slot does support heaps of features, like Target Disk Mode, S.M.A.R.T.-status, Native Command Queuing, daisy-chaining (with very low latency) making it ideal for many professional applications (Audio/Visual devices), bi-directional bandwidth, DisplayPort, 10 Watt of power and native software driver support.
Just to name a few.
External SATA doesn't do the same either.
Thunderbolt is a multi-purpose connector, not limited to only storage or transfer of files.
If you for a minute think that USB or E-SATA does the same as Thunderbolt, then you need to educate yourself.
It has the potential to replace all other external connectors. One cable to rule them all, instead of legacy cables that clutter up the backside of your computer and collect dust.
Anato - Friday, July 8, 2011 - link
And one controller (maker) to rule us all. Thats a big problem in PC, but not necessarily in Mac.Jaybus - Sunday, July 10, 2011 - link
Not really. Light Peak is essentially protocol agnostic. It tunnels PCI-E. The PCI-E-to-whatever bridge is built into the cable and/or dongle. In other words, a USB 3.0 adapter/hub that plugs into a Light Peak port is possible and even likely.While Intel may control the Light Peak controller, which will no doubt be integrated into motherboard chipsets, I don't think that will give them a monopoly on the bridge chips that make LP actually useful.Exodite - Friday, July 8, 2011 - link
Cue 'potential'.It's not hard to foresee another Firewire or mini-DP in the making, or a Beta if you prefer going old-school.
Coupling Light Peak technology with mini-DP was a mistake. The technology is new, unproven and offers precious few usage scenarios with non-existent device support. Piggy-backing it on mini-DP, which suffer from pretty much exactly the same issues, won't help adoption rates.
Choosing USB over mini-DP as the 'legacy' interface would have been a much better choice.
André - Friday, July 8, 2011 - link
Except that the USB connector is only allowed to be used as an USB connector.DisplayPort is also vastly superior to any other display cable standard, so I cannot see the problem in that regard. Mini-Display is already shipping in millions and millions of computers, as well as Mini-DisplayPort. The same can be said by Thunderbolt, even though it is only Apple who have fully embraced the technology.
As a professional in the audio/visual segment I can hardly see the problem with it being a repeat of FireWire, because my market usually adopts the better technology despite of a small price increase. Of course, it helps that we only use Apple computers to begin with and have already ditched all the back-alley, legacy connectors.
Uritziel - Friday, July 8, 2011 - link
Heh, yet another continuation of the myth that media professionals only use macs...André - Friday, July 8, 2011 - link
Kindly don't put words in my mouth ;)I didn't say media professionals only use Apple computers, I said my company only use them.
As for now it only makes sense to discuss Thunderbolt and Apple computers as Apple are the only ones who has it currently.
But you just have to look at the companies that are releasing Thunderbolt enabled devices to understand that this connector is really something professionals are going to use. Next year the market will open up when PC vendors finally, if they so choose, to embrace the technology.