S3 vs THD hardware differences

Both use comparable MIPS processors running @ 300MHz. Broadcom quotes 450 DMIPS for the BCM7401 and quoted 420 DMIPS for the BCM7038 in the past. It is not entirely clear whether hardware performance improved, or whether compiler technology improved in the time between the release of the BCM7038 (August, 2004) and the BCM7401 (January, 2006).

The memory controllers are comparable. Both use a 64-bit 400MHz DDR interface. The TiVoHD and Series3 both have DDR400.

The TiVoHD has 256Mb DDR400 dedicated to its BCM7401 while the Series3 has 128Mb DDR400 dedicated to its BCM7038. The Series3 also has another 128Mb dedicated to the BCM7411 (for MPEG-4 / AVC support), but neither that chip nor its memory is currently used. As of the 8.x software, the TivoHD and Series3 were both using about the same amount of memory -- leaving most of the memory on the TivoHD free and unused.

The BCM7038 in the TiVo Series3 does have an extra decoder. From what I understand, the BCM7038 can decode two streams simultaneously, but its bandwidth limits output to one HD and one SD at any given time. Some older Dish Network HDTV DVRs use the BCM7038 to provide picture-in-picture functionality. TiVo does not take advantage of the second decoder to provide PIP or dual-TV support on the TiVo Series3. It is doubtful they ever will, since the BCM7401 in the TiVoHD does not have the second decoder.

Another difference is the extra SATA port on the BCM7038. The BCM7401 only has a single SATA port, so TiVo was forced to use a Silicon Image port multiplier -- splitting one SATA port into two -- to provide support for eSATA storage on the TivoHD.

 

Whatever the hardware specs are, in the real world the Series 3 is snappier than the TiVo HD.

 

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I initially was focusing on the hardware specifics too, but these are hard to evaluate from the outside without the benefit of “system” knowledge. On a more general level, it seems to me that the primary design goal of the S3 was high performance (higher encode bit rates, THX certified, OLED display, faster transfers, etc).

But people complained about the price, so the Tivo HD was born, and the primary design goal for the Tivo HD was low cost.

Now, cost and quality are not necessarily mutually exclusive, but…

If you check the posts, you will see cases where people took back their HD and got an S3 due to various issues. I realize that the HD’s drivers aren’t as mature as the S3’s, and things should improve with time for the HD, but I also wonder if some of the HD’s issues are hardware related due to cost cutting.

I just ordered an S3 in hopes of avoiding some of the issues that seem to be more common with the HD right now. The S3 just seems to be the more robust unit currently.

Oh, by the way, the S3 is much better looking than the HD!

 

Personal experience with both and side-by-side comparisons of speed through the menus and latency with things like 30 second skip and replay and navigating through menus.

It's not particularly objectionable all alone, but when you also have Series 3 units you use it's a disconcerting difference -- especially the additional latency which I can only guess is caused by some different signal processing/overlay paths in the new graphic chipset they use in the TiVo HD.