1001FALS transfer rate problem

Hello, I’m facing the following problem :

  • I have a 5000AAKS and a 1001FALS on my system running Windows XP on an ASUS P5K-E motherboard

  • Some time ago I noticed that the 1TB Caviar Black (1001FALS) started performing poorly. I ran HD Tune Pro and found that, in the benchmark section, 1001FALS could reach at most 4.2 MB/s when reading. The other one (the 500GB Caviar Black) ran fine, reaching reading speeds of 70-80MB/s. I moved the FALS on another SATA slot, and it started working fine (the benchmark showed speeds of over 100MB/s). But, after awhile (a few days or so) the problem reappeared (after booting the PC, the FALS started performing poorly). Moving the FALS on another SATA slot will sometimes make it work (for awhile, as I said before). When working ‘properly’ and continously reading from the HDD (watching a movie), it sometimes gets ‘stuck’, it is as if it attempts to read some data, but fails and it retries for about 20-30 seconds, staying in this loop - the HDD indicator is showing activity during this time.

  • I tried a lot of different cables, enough to be sure that the cable wasn’t the issue

In conclusion :

  • 1001 FALS performs really bad - reading speeds up to 4.2 MB/s

  • moving it on another SATA slot will fix this temporarily

  • when working at normal speeds, the HDD sometimes gets stuck trying to access data

  • SATA cable not an issue

In the Health tab of HDD Tune Pro, the Reallocated Sector Count shows 100 and Current Pending Sector shows 270. Any ideas regarding this ?

It appears that your drive may be running in PIO mode. Windows XP will downgrade a drive’s performance from DMA mode to PIO mode if it detects more than 6 CRC errors.

DMA Mode for ATA/ATAPI Devices in Windows XP:

DMA reverts to PIO:


Is your SATA controller configured in BIOS for IDE, legacy, or compatibility mode?

Could we see the actual benchmark graphs and SMART data? If the drive is running in PIO mode, then the benchmark result will be a flat line.


Indeed the problem was as you anticipated, but what makes windows switch to PIO mode is a mystery to me. I used the vbs script on the second site to make Windows revert to DMA mode and now it works at the right speed. I also attached the Health status. In BIOS, I have the following (reproduced by memory, hope it’s correct) :

 - SATA Configuration : Enhanced / Compatible

 - SATA Configured As : IDE / AHCI / RAID

ISTM that the drive is recording an excessive number of errors, which results in Windows XP dropping back to PIO mode. The Seek Error Rate is also suggesting a problem, possibly with one particular read head. The highest recorded operating temperature appears to have been 37C (= 150 - 113), so that 's not a factor. IMHO you should backup and be ready to replace your drive. :frowning:

It’s just two or three months old. That’s a shame,I always thought of WD HDDs as being the most reliable. That being said, I’ll try my luck with another Caviar Black, when working right they seem to offer the best performance for the money. It really feels like drawing straws to me now and with my previous purchase, I drew a particularily short one. Maybe second time’s the charm ?