Skip to content

Home

Jump to bottom
Ulrich Stern edited this page Mar 24, 2023 · 16 revisions

Dell Issues

System board or BIOS issues with Dell machines.

Why?

I used to be a fan of Dell machines -- we purchased 12 Dell XPS desktops over the years in our neurobio lab as lab servers, but the recent XPS 8940 and 8950 have been unreliable enough that I am considering switching vendor. Reliability is quite important for us since the machines often control experiments running over multiple hours or even days, and a crash can set us back for multiple weeks since it can cause data loss for many experimental animals (fruit flies in our case) that take time to grow.

My hope is that this write-up will be useful for

  • Dell engineers to help them debug their machines.
    • I tried contacting Dell Support about the issues, but the experiences felt like a waste of time. To be fair, help with sporadic issue is difficult, but I describe one of the Dell Support experiences below to show that Dell Support could improve.
    • I continue to be impressed about the reliability of our older (pre-8940) XPS machines.
  • Dell customers interested in using the XPS 8940 and 8950 in applications where high reliability is critical.

XPS 8940

The XPS 8940 can sporadically freeze (crash), requiring a reboot, the freezes are quite likely triggered by USB activity, and downgrading to 10th-gen Intel CPUs fixes the freezing issue! The XPS 8940 supports both 10th- and 11th-gen CPUs.

Our data on this issue is quite good:

  • we have 5 of the XPS 8940 in our lab.
  • the freezes happened for all of the machines using 11th-gen CPUs and under different versions of Ubuntu, 18.04, 20.04, and 22.04.
  • after downgrading two of the machines to 10th-gen CPUs (i9-10900K), the freezes on them never reoccurred.
  • the freezes happened maybe half of the time without user interaction during experiments, when fruit flies were tracked in real-time using multiple USB webcams causing relatively high USB load; most of the remaining crashes happened upon (USB) mouse movement, often to wake up the screen prior to attempting to log in.
    • due to the clear temporal correlation with mouse movement in a sufficiently large number of freezes, an issue with USB handling on XPS 8940 with 11th-gen CPUs seems very likely the root cause of the freezes.
    • /var/log/syslog never contained any info that looked like a kernel issue is to blame, regardless of Ubuntu version, and in some cases there were multiple 0-valued bytes in the syslog at the time of the freeze.
    • it seems likely Dell's BIOS is the root cause of the issue, since this seems more likely than a bug in Intel's 11th-gen CPUs or a bug in multiple versions of Ubuntu.

XPS 8950

The XPS 8950 may have a system board issue that causes sporadic memory errors, which, of course, can cause crashes, data corruption, etc. I am not certain this is limited to our machine (we have only a single XPS 8950) or a design flaw in the system board.

Here the data:

  • I have been running MemTest86 on the machine since we bought it.
  • MemTest86 regularly identifiers memory errors -- sometimes after running less than day, sometimes after multiple days.
    • the errors appear at random locations, making a system board issue more likely than a memory module issue.
    • due to the high reliability requirements of our application, a memory error every few days rules out the machine.
    • I plan to post the full error details soon.
  • to rule out an issue with the original memory modules in the machine, I replaced them with a Crucial module, but this did not solve the issue.
  • the memory speed dropped to about 17.8 GB/s starting with BIOS 1.7.0 from about 24.4 GB/s with earlier BIOS versions. The slower speed did not solve the issue.
  • I regularly update to the latest BIOS, hoping the issue is fixable this way; with 1.11.1, the issue still occurs.
  • during one of my calls with Dell Support, I was asked to run their built-in (BIOS) diagnostics; the memory passed, which is not surprising for a less than 1-h test. But the machine froze after the test while still inside Dell diagnostics! The Dell Support person I talked to insisted that only Dell's diagnostic counts for hardware issues, despite the fact that MemTest86 seems the industry standard for memory testing.

Clone this wiki locally