how to measure DVD drive power under full speed

Don't see a specific place for your hardware question? This is the forum for you!

Moderators: mac_h8r1, Nemesis

how to measure DVD drive power under full speed

Postposted on Tue Feb 05, 2013 8:23 pm

is there any easy way (without having any measuring hardware device) to calculate how much a DVD drive uses for a computer or console under full speed? like an Xbox 360 game spinning at 12X sounds like a jet and sounds like it consumes a lot of power.
onlysublime
Gerbil
 
Posts: 81
Joined: Sat Jul 16, 2005 3:20 pm

Re: how to measure DVD drive power under full speed

Postposted on Tue Feb 05, 2013 10:19 pm

Not as much as you might think -- one of the virtues of a spinning disc is that it wants to keep spinning.

I don't know about the XBox component in particular but there plenty of USB-powered external drives, suggesting it is easy to keep them under 5W.
UberGerbil
Gerbil Khan
 
Posts: 9990
Joined: Thu Jun 19, 2003 3:11 pm

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 11:55 am

The sound is a function of the rotational speed, which produces high-frequency bearing noise and corresponding air disturbance within the drive. Optical discs read at constant linear velocity, which means the inner tracks (where the disc diameter is small) have to spin faster than for outer tracks (where the disc diameter is large). Some quick lookup indicates that CD-1X varies from 500 RPM down to 350 RPM, and DVD-1X varies from 1530 RPM down to 630 RPM.

So, a DVD-12X drive could attempt to spin the disk in excess of 18,000 RPM at the inner tracks, which for comparison, is roughly 1.8 times the speed of a large jet turbine, and about the same as a Dremel tool operating at half-speed.
He who laughs last, laughs first next time.
ludi
Gerbil Elder
 
Posts: 5441
Joined: Fri Jun 21, 2002 10:47 pm
Location: Sunny Colorado front range

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 12:39 pm

Looks like the DVD mechanism makers have thoughtfully stopped printing the device's power consumption on the device or showing it anywhere on their product's info pages. Must be some big huge hairy secret now.

Anyway, one answer appears to be around 4.5W during spin-up. This would not include power needed by the laser for burning, but maybe someone else knows this number.
This problem was caused by Windows, which was created by Microsoft Corporation.
sluggo
Gerbil Jedi
Gold subscriber
 
 
Posts: 1542
Joined: Wed Feb 16, 2005 8:44 pm
Location: under the table and dreaming

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 12:47 pm

ludi wrote:So, a DVD-12X drive could attempt to spin the disk in excess of 18,000 RPM at the inner tracks, which for comparison, is roughly 1.8 times the speed of a large jet turbine, and about the same as a Dremel tool operating at half-speed.

...and more than double the speed of a typical consumer hard drive!

You're also talking about a 20 cent piece of plastic, which isn't manufacturered to anywhere near the tolerances of a hard drive platter. It's actually kind of amazing they don't cause excessive vibration or fail (fly apart due to the mechanical stresses of being spun at 18,000 RPM) more often than they do.
(this space intentionally left blank)
just brew it!
Administrator
Gold subscriber
 
 
Posts: 37739
Joined: Tue Aug 20, 2002 10:51 pm
Location: Somewhere, having a beer

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 12:52 pm

just brew it! wrote:
ludi wrote:So, a DVD-12X drive could attempt to spin the disk in excess of 18,000 RPM at the inner tracks, which for comparison, is roughly 1.8 times the speed of a large jet turbine, and about the same as a Dremel tool operating at half-speed.

...and more than double the speed of a typical consumer hard drive!

You're also talking about a 20 cent piece of plastic, which isn't manufacturered to anywhere near the tolerances of a hard drive platter. It's actually kind of amazing they don't cause excessive vibration or fail (fly apart due to the mechanical stresses of being spun at 18,000 RPM) more often than they do.


Well, HD platters are designed to spin at 7200/whatever RPM constantly for years on end. CD/DVD/HDDVD/Blu-Rays? Not so much. Even if they get spun faster, much faster, they also don't spin nearly as long.
I.S.T.
Gerbil First Class
 
Posts: 178
Joined: Wed Sep 14, 2005 5:18 am

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 12:53 pm

ludi wrote:So, a DVD-12X drive could attempt to spin the disk in excess of 18,000 RPM at the inner tracks, which for comparison, is roughly 1.8 times the speed of a large jet turbine, and about the same as a Dremel tool operating at half-speed.

And at about 23,000 RPM they tend to self-disassemble rather spectacularly.
Life is hard; but it's harder if you're stupid. Big Al.
Captain Ned
Global Moderator
Gold subscriber
 
 
Posts: 20313
Joined: Wed Jan 16, 2002 7:00 pm
Location: Vermont, USA

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 12:53 pm

sluggo wrote:Anyway, one answer appears to be around 4.5W during spin-up. This would not include power needed by the laser for burning, but maybe someone else knows this number.

They appear to have tested video playback software only, which only needs to spin the disc at 1x. So even reading a data DVD may result in higher numbers.

Edit: I imagine there's a big difference between internal and external. With an external drive they probably ramp the speed up more gradually, to stay within the 2.5W (5W with a Y cable) USB power limit.
(this space intentionally left blank)
just brew it!
Administrator
Gold subscriber
 
 
Posts: 37739
Joined: Tue Aug 20, 2002 10:51 pm
Location: Somewhere, having a beer

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 1:00 pm

I.S.T. wrote:Well, HD platters are designed to spin at 7200/whatever RPM constantly for years on end. CD/DVD/HDDVD/Blu-Rays? Not so much. Even if they get spun faster, much faster, they also don't spin nearly as long.

Regardless, it's pretty amazing that they are able to keep vibration to reasonable levels. IIRC many drives have a clever arrangement of steel ball bearings and magnets inside the hub clamp, which redistribute themselves to counteract the vibration caused by unbalanced discs. So the drives are able to compensate (to an extent) for mechanical imperfections.
(this space intentionally left blank)
just brew it!
Administrator
Gold subscriber
 
 
Posts: 37739
Joined: Tue Aug 20, 2002 10:51 pm
Location: Somewhere, having a beer

Re: how to measure DVD drive power under full speed

Postposted on Wed Feb 06, 2013 1:14 pm

just brew it! wrote:IIRC many drives have a clever arrangement of steel ball bearings and magnets inside the hub clamp, which redistribute themselves to counteract the vibration caused by unbalanced discs. So the drives are able to compensate (to an extent) for mechanical imperfections.

Which is why older Lite-Ons sound so thrashy at high speeds.
Life is hard; but it's harder if you're stupid. Big Al.
Captain Ned
Global Moderator
Gold subscriber
 
 
Posts: 20313
Joined: Wed Jan 16, 2002 7:00 pm
Location: Vermont, USA

Re: how to measure DVD drive power under full speed

Postposted on Mon Feb 11, 2013 10:06 pm

wow. I learn so much from you guys... :D

well, if the limit of a power cable is 5 W, I guess that's the answer there.

as for the speed, are modern drives CAV or CLV? and doesn't the outside of the disc spin faster and read data faster as a result?
onlysublime
Gerbil
 
Posts: 81
Joined: Sat Jul 16, 2005 3:20 pm

Re: how to measure DVD drive power under full speed

Postposted on Mon Feb 11, 2013 10:25 pm

onlysublime wrote:wow. I learn so much from you guys... :D

well, if the limit of a power cable is 5 W, I guess that's the answer there.

That's the limit for external USB drives. But the point is, if an external USB one is limited to 5W an internal one of comparable vintage and speed probably isn't a *whole* lot worse. Early external burners required their own power brick, so they've definitely reduced the power requirements over the years.

onlysublime wrote:as for the speed, are modern drives CAV or CLV? and doesn't the outside of the disc spin faster and read data faster as a result?

When operating in data mode they are CAV, and yes the outer area of the disc has higher throughput as a result. This is why the maximum throughput spec for DVD drives is rarely achieved in practice -- you only get the rated maximum speed when burning/reading the outermost area of a nearly full disc! Although the drive is nominally CAV, spindle speed can still be ramped up/down for power management purposes, due to user request (e.g. reduced burn speed to improve the reliability of the burn), or when the drive is attempting to recover data from a marginal sector.

When playing audio and video discs the drive switches to CLV mode, since it needs to maintain whatever bitrate the content was encoded at.
(this space intentionally left blank)
just brew it!
Administrator
Gold subscriber
 
 
Posts: 37739
Joined: Tue Aug 20, 2002 10:51 pm
Location: Somewhere, having a beer

Re: how to measure DVD drive power under full speed

Postposted on Tue Feb 12, 2013 11:23 pm

I.S.T. wrote:
just brew it! wrote:
ludi wrote:So, a DVD-12X drive could attempt to spin the disk in excess of 18,000 RPM at the inner tracks, which for comparison, is roughly 1.8 times the speed of a large jet turbine, and about the same as a Dremel tool operating at half-speed.

...and more than double the speed of a typical consumer hard drive!

You're also talking about a 20 cent piece of plastic, which isn't manufacturered to anywhere near the tolerances of a hard drive platter. It's actually kind of amazing they don't cause excessive vibration or fail (fly apart due to the mechanical stresses of being spun at 18,000 RPM) more often than they do.


Well, HD platters are designed to spin at 7200/whatever RPM constantly for years on end. CD/DVD/HDDVD/Blu-Rays? Not so much. Even if they get spun faster, much faster, they also don't spin nearly as long.


well, I think gaming consoles are pushing the limits here. I know friends who play for hours and that drive spins fast the entire time the game is running (by noise level, most of the time it seems half as loud but the major data loading (to load the next level), it spins at full speed and sounds like the jet). Most of them end up installing the game to the hard drive so they don't kill the DVD drive and to reduce the noise. also a console has a lot of loading and unloading because the RAM is so small (512 MB for Xbox and 256 MB for PS3).

but yes, they don't have the same uptime as a PC hard drive.
onlysublime
Gerbil
 
Posts: 81
Joined: Sat Jul 16, 2005 3:20 pm


Return to General Hardware

Who is online

Users browsing this forum: Bing [Bot] and 4 guests