An Analysis of TiVo Series2 DT 649-series Network Throughput Capability

[Cabal]

Objective

To test bandwidth capabilities of a stock, unhacked TiVo Series2 DT and determine any contributing factors to throughput.

Background

http://en.wikipedia.org/wiki/TiVo_DVRs
http://en.wikipedia.org/wiki/TiVo_DVRs#Series2
http://www.broadcom.com/products/Satellite/Satellite-Set-Top-Box-Solutions/BCM7318

Test Unit

Tivo Series2 DT 649-series
CPU: Broadcom BCM7138, 266 MHz MIPS
RAM: 64 MB of 133 MHz 16-bit DDR
MPEG Encoder: Two Broadcom BCM7042
Hard Drive: 80 GB
Network: Onboard ethernet, negotiated at 100 mbps full-duplex
Software: 8.1a

Methodology

Testing was done with Curl and the HTTP interface on a mostly-idle, switched, gigabit ethernet network. Each test used a 500 MB file, left running to get an accurate sustained speed, and repeated 5+ times for accuracy. Results were sanity-checked with a browser and TivoToGo. Use of Curl was as follows:

curl -k --digest -u tivo:XXX -c /dev/null -o test.tivo $URL

Results

http://home.comcast.net/~axp696/tivo_speeds.jpg

Observations

- The tests were all extremely consistent. They reached top speed immediately, and rarely deviated by more than 10 KB/s.
- Decoding has a significantly greater effect on throughput than encoding.
- Encoding has a small effect on throughput, but shouldn't be discounted entirely.

Conclusions
- Bandwidth is limited by the processing power of the BCM7318 chip, which covers decoding, general processing, and ethernet.
- The best speed gains, upwards of 25%, can be had by limiting the decoding work of the unit. The blue non-channels (1, 99, etc) work best for this.
- The best transfer rates are achieved with both tuners viewing blue non-channels. This configuration is recommended for GB+ transfers when viewing is not necessary.

Comments, arguments, or further analysis welcome.

[Dan203]

Either way the speeds of the DT unit are pretty impressive. With my Toshiba DVD-RW unit I'm lucky to get 175KB/s even when I tune it to a blue channel first.

Dan

[donchanger]

Interesting.

I will just add that using a Tivo Wireless G, a very plain home wireless network (cheap D-Link router), and a marginal signal, I can usually get close to 900 KB/sec with the unit in "Standby" (no idea what channels the tuners might have been on before "Standby").

[suomynona]

Here's an idiotic question. What's a blue channel?

[Cabal]

Here's an idiotic question. What's a blue channel?
Not a dumb question, I didn't spell it out. A blue channel is one where you aren't receiving any signal, such as 1 or 98 or 99 possibly, where the TiVo will jump to a blue screen with text saying you aren't receiving a signal. This will halt one of the encoding streams.

[yukit]

Anyone know a similar test result for 240 & 540 series units?

My 240 unit connected to a WinXP machine running Desktop 2.4 works fairly well, but the 540 unit connected to Vista with Desktop 2.3a is really slow & causes frequest Tivo reboots.

[Cabal]

I re-ran some quick tests now that I've settled in with 9.1, and I get a pretty steady 1.5-1.6 MB/s (1500-1600 KB/s, 12-12.8 Mbps) with both tuners set to null channels. They no longer give the big blue screen and instead show a smaller tuner error message, but channels 1 and 99 continue to have the same effect on transfer rate. :up:

[CuriousMark]

Anyone know a similar test result for 240 & 540 series units?
Look at my old test results here (http://www.tivocommunity.com/tivo-vb/showthread.php?p=3671834#post3671834).

Reboots are not normal, you may have a failing hard drive.