The impact of NCQ on Multitasking Performance

Last June I reviewed Maxtor's MaXLine III, the first SATA drive to bring a 16MB buffer and NCQ to the desktop. In that article I looked at NCQ as a feature that truly came to life when working in multitasking scenarios, unfortunately finding a benchmark to support this theory was difficult. In fact, only one benchmark (the first Multitasking Business Winstone 2004 test) actually showed a significant performance improvement due to NCQ.

Last night, after recovering from Part I and realizing that my nForce4 Intel Edition platform had died, I was hard at work on Part II of the dual core story. For the most part when someone like AMD, Intel, ATI or NVIDIA launches a new part, they just send that particular product. In the event that the new product requires another one (such as a new motherboard/chipset) to work properly, they will sometimes send both and maybe even throw in some memory if that's also a more rare item. Every now and then one of these companies will decide to actually build a complete system and ship that for review. For us, that usually means that we get a much larger box and we have to spend a little more time pulling the motherboard out of the case so we can test it out on one of our test benches instead - obviously we never test a pre-configured system supplied by any manufacturer. This time around, both Intel and NVIDIA sent out fully configured systems for their separate reviews - great, two huge boxes blocking our front door now.

When dissecting the Intel system I noticed something, it used a SATA Seagate Barracuda 7200.7 with NCQ support. Our normal testbed hard drive is a 7200.7 Plus, basically the same drive without NCQ support. I decided to make Part I's system configuration as real world as possible and I used the 7200.7 with NCQ support. So I used that one 7200.7 NCQ drive for all of the tests for Monday's review. Normally only being able to run one system at a time would be a limitation, but given how much work I had to put into creating the tests I wasn't going to be able to run multiple things at the same time while actually using each machine so this wasn't a major issue. The results turned out as you saw in the first article and I went on with working on Part II.

For Part II I was planning on creating a couple more benchmarks, so I wasn't expecting to be able to compare things directly to Part I. So I switched back to our normal testbed HDD, the 7200.7 Plus. Using our normal testbed HDD, I was able to setup more systems in parallel (since I had more HDDs) and thus testing went a lot quicker. I finished all of the normal single threaded application benchmarks around 3AM (yes including gaming tests) and I started installing all of the programs for my multitasking scenarios.

This morning when I went to run the first multitasking scenario, I noticed something was very off - the DVD Shrink times were almost twice what they were in Monday's review. I spent more time working with the systems and uncovered that Firefox and iTunes weren't configured identically to the systems in Monday's review, so I fixed those problems and re-ran. Even after re-running, something still wasn't right - the performance was still a lot slower. It was fine in all other applications and tests, just not this one. I even ran the second multitasking scenario from Monday's review and the performance was dead on, something was definitely up. Then it hit me...NCQ.

I ghosted my non-NCQ drive (thanks OzzFan :)) to the NCQ drive and re-ran the test, yep, same results as Monday. The difference was NCQ! Johan had been pushing me to use a Raptor in the tests to see how much of an impact disk performance had on them, and the Raptor sped things up a bit, but not nearly as much as using the 7200.7 did. How much of a performance difference? Well, I hate to be the type to leave you in suspense so I'll post my numbers here before they go live in Part II. The following numbers use the same configuration from Monday's article, with the only variable being the HDD. I tested on the Athlon 64 FX-55 system:

Seagate Barracuda 7200.7 NCQ - 25.2 minutes
Seagate Barracuda 7200.7 no NCQ - 33.6 minutes
Western Digital Raptor WD740 - 30.9 minutes

The performance impact of NCQ is huge. But once again, just like the first NCQ article, this is the only test that I can get to be impacted by NCQ. It's a very strange beast...and things get even stranger.

The benchmark is super repeatable on the Athlon 64 FX-55, these results are consistent regardless of how many times I run them. The dual core Pentium D 3.2 doesn't produce such consistent results, it still shows a positive performance impact due to NCQ but I'm not sure of the actual percentage. Now that I'm comfortable with the AMD results I'm going to focus on the Intel results a bit to see if a single threaded (non HT) Intel chip gets a similar benefit from NCQ.

I originally was going to focus an entire article on the impacts of NCQ on multitasking performance but right now with only one benchmark showing its impact, there's not much of an article there :) Instead, I'm going to roll it into Part II of the dual core series. And of course, you all got the scoop here first.

Back to testing...