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 | ||
Facebook
Twitter
RSS
88 Comments
View All Comments
darwinosx - Friday, July 8, 2011 - link
All two or three devices? By end of year there will be a flood of consumer devices with Thunderbolt ports.epobirs - Friday, July 8, 2011 - link
Not if apple remains the sole platform including it. Niche markets can be expensive. Until Thunderbolt is an option in Windows systems the numbers just won't be there for the consumer market. The devices will continue to be expensive for most non-professional Apple users as well, making this a very expensive product category.Consider the premium USB 3.0 is still carrying almost a year after it started being included in shipping systems and widely available as an upgrade via PCI-e board. This past week was the first time I saw a USB 3.0 flash drive priced low enough to be worthwhile. Frys had a 16 GB Corsair unit for $20 after rebate. Note that this unit is almost 50% larger than the USB 2.0 version and so may not be acceptable to all.
Next year, as motherboard chip sets with native USB 3.0 support enter the mainstream the transition should pick up steam. It's taken more than three years since the first controllers became widely available. So try toimagine the glacial growth rate for Thunderbolt outside professional applications if it doesn't get a decent footprint beyond the Mac.
iwod - Friday, July 8, 2011 - link
AOC recently announce a Monitor that can be powered by 2 USB, roughly 9W. Which means it it really did worked out. A Thunderblot version could be possible, having an external monitor with just 1 cable!!!.MobiusStrip - Tuesday, July 12, 2011 - link
And at least Thunderbolt is an appropriate conduit for video, which USB is not.cactusdog - Friday, July 8, 2011 - link
Haha the motherboard makers are gonna run out of space putting all these different connections. Maybe they can retire some like firewire....Anyway, any chance of a review of the Samsung S27A950D 120Hz monitor? Alotta people are interested. Thanks.
xype - Friday, July 8, 2011 - link
Retire FireWire, but leave the VGA, Serial, Parallel ports. That would totally make sense.Exodite - Friday, July 8, 2011 - link
VGA still makes sense, on account to the large numbers of projectors in circulation making use of it.As for the others, not so much.
Anato - Friday, July 8, 2011 - link
Y, but it still could be substituted with Displayport/Thunderbolt and make an adapter for VGA/DVI/HDMI.I hate to see VGA as only option in computers costing 2000€ :(
Exodite - Friday, July 8, 2011 - link
You can already do that.All you have to do is pay through the nose for three adapters (VGA, DVI and HDMI) and carry them with you at all times.
Personally I wouldn't buy a notebook without native VGA output, preferably coupled with HDMI.
repoman27 - Saturday, July 9, 2011 - link
OK, I recognize that most A/V equipment isn’t refreshed as often as PCs are, but the industry started the switch to digital display interfaces 12 years ago. If you really can’t part with your equipment that predates DVI, you can pick up an Apple mini DisplayPort to VGA adapter for $29, or a generic one for $5. It’ll fit in your pocket, and yes it will work with the Thunderbolt equipped Macs. And hey, now that you’ve got an analog signal, it’s no problem to use a passive adapter to convert to s-video or composite video, and then you can attach it right to your RF modulator and drive any TV made since 1941. Complete backwards compatibility for under $15 that will fit in your pocket (although you’ll probably need cargo pants for the RF modulator.)If you can confine yourself to connecting to displays manufactured in the last 10 years or so, you can get an Apple DisplayPort to DVI adapter for $29, or a generic one for $5. It’ll fit in your pocket, and yes it will work with the Thunderbolt equipped Macs. Combine that with a DVI to HDMI cable for an additional $2, and now you can connect to any display with a digital interface except those requiring dual-link DVI. If you want audio as well as video over HDMI, you can get a mini DP to HDMI adapter such as the super slick Griffin GC17096 with Audio and DVI for $27, or go generic for far less.
The only cumbersome and expensive conversion on the newer Macs is when you absolutely have to go the dual-link DVI route. This requires an active adapter that has to regenerate the video signal. The apple version will run you $99 (see, those TB cables aren’t so expensive after all). However, Thunderbolt may actually allow for cheaper and more elegant solutions due to sufficient power being available on the port. Then again, dual-link DVI only displays are cumbersome and expensive in and of themselves, so it shouldn’t matter too much to those who actually own one.
The whole point of Thunderbolt is that it’s NOT yet another connection, it’s a radical extension of the capabilities of one you already have—the video out port. The only digital display interfaces that are even remotely as versatile, capable or compact as mini DP are mini/micro HDMI, but their consumer electronics heritage presents some drawbacks for PC applications. Not to mention that it is the packetized nature of the DisplayPort protocol itself that allows it to be combined with PCIe on a single link to create Thunderbolt. VGA ports are literally 8 times the size of mini DP ports and DVI are larger still. By forcing those who need to connect to 10 year old equipment to carry a $5 adapter in their pockets when they might need to do so, manufacturers are able to give everyone an additional 15 minutes of power when running on battery.