# Buffer to RAM to reduce power usage



## Traal (Jul 8, 2002)

With enough RAM (about 1.5GB per tuner to hold 30 minutes of HD video), the hard drive wouldn't need to spin 24/7. This should reduce TiVo's power usage by an order of magnitude.


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## aaronwt (Jan 31, 2002)

Traal said:


> With enough RAM (about 1.5GB per tuner to hold 30 minutes of HD video), the hard drive wouldn't need to spin 24/7. This should reduce TiVo's power usage by an order of magnitude.


It would not reduce it by an order of magnitude. The WD A/V drives use less than 4.5 watts of power. The TiVo uses over 20 watts. It would only decrease it by around 20%. Not from 20 watts down to 2 watts.


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## waynomo (Nov 9, 2002)

What would be the effect of having the drives start and stop?

I would think this could lead to a higher failure rate.


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## jrtroo (Feb 4, 2008)

and there are many disputes about wear and tear on the drives. Most literature has demonstrated that spin up/down cycle causes more wear. And, the marginal cost of this memory would need to be figured in. Hnmm, i think tivo is expensive enough- if you want to save minimal costs feel free to put it on a timer, seems to work for some folks willing to take the risk.


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## Traal (Jul 8, 2002)

aaronwt said:


> It would only decrease it by around 20%.


Good point. Well, it's a start. Streaming video players only consume around 5W total.



jrtroo said:


> Most literature has demonstrated that spin up/down cycle causes more wear.


Really aggressive spin up/down cycles do (like powering down after 8 seconds of inactivity), but on a TiVo the period would be on the order of hours and not seconds.



jrtroo said:


> And, the marginal cost of this memory would need to be figured in.


About $15 per tuner at today's prices, or around $7 per tuner at last December's prices.


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## jrtroo (Feb 4, 2008)

Then just put it on a timer yourself, way more savings there than your suggestion.

Marginal costs of hardware escalates once build into a retail unit.


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## Traal (Jul 8, 2002)

jrtroo said:


> Then just put it on a timer yourself...


No.


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## Dan203 (Apr 17, 2000)

Impossible. At 19.2Mbps* each tuner would require about 4.32GB of RAM to buffer 30 minutes. So for a 6 tuner TiVo it would need about 26GB of RAM. In order to be able to address that much memory they would need a 64bit processor. AFAIK all current SOCs from Broadcom are still 32bit.

*19.2Mbps is the max bitrate for ATSC but technically cable could go higher if they wanted so they may need more RAM just in case.


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## Jonathan_S (Oct 23, 2001)

Dan203 said:


> Impossible. At 19.2Mbps* each tuner would require about 4.32GB of RAM to buffer 30 minutes. So for a 6 tuner TiVo it would need about 26GB of RAM. In order to be able to address that much memory they would need a 64bit processor. AFAIK all current SOCs from Broadcom are still 32bit.
> 
> *19.2Mbps is the max bitrate for ATSC but technically cable could go higher if they wanted so they may need more RAM just in case.


And even at today's RAM prices 26 GB of RAM is probably a couple hundred bucks (even wholesale). That'd be an _expensive_ way to save a small amount of power.


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## Traal (Jul 8, 2002)

At any given time, most tuners are idle (not being watched) or recording. Neither of these uses require a buffer. So this presents an opportunity to conserve buffer memory.


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## jrtroo (Feb 4, 2008)

All tuners are always recording, always. The fact that only one can be seen at any give time (though this is not true anymore with the Mini) does not mean that the others are not being recorded and buffered, so there is never any idle time for the drive. Simply, there is no cost benefit to be found unless you turn off the drive (eg, the tivo) altogether and get lucky and do not cause the drive to die an early death.


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## Traal (Jul 8, 2002)

jrtroo said:


> All tuners are always recording, always.


No, they're always buffering. They only have to buffer when they're being watched but not recording.


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## jakerock (Dec 9, 2002)

Buffering IS recording. You're recording the stream of data into a buffer which is on the hard drive. You could record it into a RAM buffer if you had enough RAM to store 2, 4, or 6 streams at once (depending on the unit) but you do have to cover all the receivers.

If I swap between receivers I can view the last 30 minutes of the content on that receiver. It's been recorded (into a buffer if you want to call it that) onto the hard drive and if you want to replace the hard drive with RAM then you need to have enough RAM to do it (or else you're changing how the system works).


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## Dan203 (Apr 17, 2000)

Traal said:


> At any given time, most tuners are idle (not being watched) or recording. Neither of these uses require a buffer. So this presents an opportunity to conserve buffer memory.


Even if this were the case you'd still need 4.32GB of RAM to store a 30 minute buffer. A 32bit CPU can only address 4GB of RAM in total, and that includes system memory and GPU memory, so it's still impossible.


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## Traal (Jul 8, 2002)

jakerock said:


> If I swap between receivers I can view the last 30 minutes of the content on that receiver.


Which is nice, but how often do you need to view the last 30 minutes from all 6 tuners?



Dan203 said:


> Even if this were the case you'd still need 4.32GB of RAM to store a 30 minute buffer. A 32bit CPU can only address 4GB of RAM in total, and that includes system memory and GPU memory, so it's still impossible.


Then I guess we need to wait until TiVo gets a CPU as powerful as the one in the iPhone 5s, or until it acquires the same technology that allowed the 8-bit TRS-80 Color Computer 3 to access up to 512KB of memory (2MB with 3rd party upgrades) almost 30 years ago.


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## Dan203 (Apr 17, 2000)

Traal said:


> Then I guess we need to wait until TiVo gets a CPU as powerful as the one in the iPhone 5s, or until it acquires the same technology that allowed the 8-bit TRS-80 Color Computer 3 to access up to 512KB of memory (2MB with 3rd party upgrades) almost 30 years ago.


TiVo is not a chip designer. They use off the shelf SOCs from Broadcom. So until Brocom releases a 64bit CPU there is nothing they can do. Plus they just released the Roamio platform, so it's unlikely we'll see another major hardware upgrade for another 5 years or so.

That being said even with 6 tuners a new Roamio only draws about 21W, which is actually less then the 2 tuner Premiere. And a Mini only draws about 6W. So if power consumption is really your main goal you could get a whole home solution today that draws significantly less power then doing the same thing just a year ago.


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## Jonathan_S (Oct 23, 2001)

Dan203 said:


> TiVo is not a chip designer. They use off the shelf SOCs from Broadcom. So until Brocom releases a 64bit CPU there is nothing they can do. Plus they just released the Roamio platform, so it's unlikely we'll see another major hardware upgrade for another 5 years or so.
> 
> That being said even with 6 tuners a new Roamio only draws about 21W, which is actually less then the 2 tuner Premiere. And a Mini only draws about 6W. So if power consumption is really your main goal you could get a whole home solution today that draws significantly less power then doing the same thing just a year ago.


Not to mention that if reduced power consumtion was an overriding design goal you could reduce it even more (and for less cost) with a config setting to simply disable buffering after x minutes of inactivity.

For most of the day the TiVo could spin down it's harddrive and tuners, and not even have to spend power buffering to RAM. [Edit: Assuming suggestions were either turned off or scheduled infrequently]

But like you said, the power consumption's been coming down with new designs anyway; so I don't really see a need for drastic steps to shave off a few more watts. <shrug>


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## jakerock (Dec 9, 2002)

Traal said:


> Which is nice, but how often do you need to view the last 30 minutes from all 6 tuners?


I don't. Just as soon as TiVo invents the technology to predict which tuners I'll want to watch in the future and only store those snippets... You really don't seem to have a clue how this works.


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## tenthplanet (Mar 5, 2004)

You would save more money by adjusting your thermostat in your house and your refrigerator.


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