Hard Drive Speed: ATA 33 versus ATA 133
March 14, 2004

Here is the question this article is tries to answer: For older computers, when you add a new modern hard drive, do you need to buy an add-in PCI IDE controller or is the onboard IDE controller fast enough?

Many of us use older hardware for servers, with good reason: webserving isn't all that CPU intensive for small sites.  Of all the old computers, the Pentium 2 and Pentium 3's are still very popular because they are decently fast and relatively inexpensive.

I have an old computer, a dual Celeron 366 overclocked to 550 on a Tyan Tiger 100 motherboard.  I recruited this computer to be my network file server and webserver test bench.  When I started to install hardware into it, I realized that the IDE hard disk controller on this BX motherboard, like all other motherboards from its time, is rated to run at 33 Megabytes per second.    Back in the day, this was plenty fast since hard drives couldn't deliver 33 MB a second anyways.  But today, we have hard drives that are rated up to 133 MB/second.

Don't be mislead by the 33 MB/second or 133 MB/second.  Your hard drive can sustain transfer rates that are much lower than those numbers would suggest.  However, your hard drive can transfer at very high rates through the onboard cache that is on all hard drives.  Most drives have at least 2 Megs of cache onboard and more and more are coming out with 8 or 16 Meg caches.  Since the cache is essentially RAM and is very quick, the cache can have burst transfers rates that are much higher than what is read directly off the hard disk platters.  These bursts only last as long as there is data in the cache.

Now, when you connect a newer fast hard drive to an older slow IDE controller, 2 things might happen.  1.  The old controller won't recognize the size of your hard drive because it's too big.  2.  If the controller does recognize the hard drive, the hard drive will be slower on the old controller than it would be on a newer faster hard disk controller.  The alternative is to buy a newer PCI IDE controller that can run at the same speed as the new hard drive.

The hard drive I plan on using with this computer is a 40 gig Maxtor DiamondMax Plus 8.  Here's the info on that drive:

Maxtor DiamondMax Plus 8

  • Capacity of 40.0 GB
  • Ultra ATA/133 
  • 2 MB Cache Buffer
  • 10 ms average Seek Time
  • 7200 RPM
Fortunately, the hard disk controller on the Tyan Tiger 100 was able to recognize the drive with no problem.  I was able to install and run Windows XP just fine.  However, I was curious how much performance difference there would be between the onboard IDE controller rated at 33 MB/second versus an add-in PCI IDE controller card that is rated at 133 MB/second.  So I decided to do a little testing.  I picked up a very popular IDE controller:

Promise Ultra 133 TX2

  • Handles up to 4 Ultra ATA/133 Drives or Devices
  • CRC Error Checking Up to 133 MB/second
I ran a simple benchmark on the hard drive when it was connected to the onboard IDE 33 MB/second controller and when it was connected to the Promise Ultra 133 TX2 133 MB/second controller.  The benchmark I used was Simpli Software - HD Tach version 2.7.  Since I didn't register this copy, I only ran the READ benchmarks:

Here is the drive on the onboard IDE disk controller on the Tiger 100 motherboard which uses a BX chipset.  This is using a standard 40 pin ribbon cable.


Here is the exact same drive on the same computer, but instead of using the onboard IDE controller, it's using a Promise Ultra 133 TX2 IDE controller in a PCI slot with a 80 pin ribbon cable.


Here is a comparison of the data from the benchmark:

Onboard IDE controller 33 MB/s
Promise Ultra 133 TX2 133 MB/s
Random Access Time
14.6 ms
14.5 ms
Read Burst Speed
30.7 MB/s
86.0 MB/s
Read Speed - Max
28.9 MB/s
64.9 MB/s
Read Speed - Minimum
15.0 MB/s
30.4 MB/s
Read Speed - Average
27.2 MB/s
52.3 MB/s
CPU Utilization

As you can see, the Promise Ultra 133 TX2 allows the hard drive to function at a much higher rate across the board at all levels, not just at the Read Burst Speed.  The values are almost double for all the categories.  For the onboard IDE controller, you can see that the 33 MB/s max is really holding back this hard drive.  For the Promise Ultra 133 TX2, you can see that although the drive is much faster, it still doesn't reach 133 MB/second, even with the Read Burst Speed which reads from the cache.  This means that using a controller that is rated up to 100 MB/s would be good enough for this drive.  In fact, I have yet to test a hard drive that exceeds 100 MB/s.  Even my Western Digital Special Edition drives with 8 Meg cache don't burst over 100 MB/s.

Aside from the benchmarks, using the computer with the hard disk connected to the  Promise Ultra 133 TX2 felt quite a bit faster than when it was connected to the onboard IDE controller.  Although you might argue that you don't do a lot of data transfers, the burst speed from the hard drive across the hard drive controller really gives the computer a snappier feel.

Now what's the bottom line?  Well, I personally think it's worth the 20 or 30 bucks to buy an add-in controller card.  It will make using an older computer feel faster and more responsive.  Also, an add-in card will recognize larger hard drives that your old onboard controller might not.  It's really up to you.  I just wanted to provide some numbers by which you can compare the same drive on 2 different controllers.

As a side note, I am a big fan of Promise hard disk controllers.  I have used almost all their controllers and have been extremely pleased.  I've found their products to be of reasonable price and good quality.  Their RAID controllers are also very good.  I use a Promise IDE RAID controller on this very webserver.  If you are thinking about IDE RAID, I highly recommend the Promise RAID controllers.  They have a solid reputation, good drivers online, and aren't too expensive.  Used Promise RAID controllers are especially a good deal and can be found on a lot of buy/sell forums on the Internet.  And no, they're not paying me to say this.  This little rant comes from years of experience using various controller cards from different companies.  I now pick Promise.

Including that last detour, this article is quite a bit longer than I had expected.  Originally I just wanted the throw up 2 screen shots and say "Hey, 133 is faster than 33".  Oh well, long live older hardware!

Take care,


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