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What is it? And what causes it?

Is it only for uncorrectable DIMM Errors(Troubleshooting DIMM errors)?

  1. When an UCE occurs, the memory controller causes an immediate reboot of the system.

  2. During reboot, the BIOS checks the Machine Check registers and determines that the previous reboot was due to an UCE, then reports this in POST after the memtest stage:

A Hypertransport Sync Flood occurred on last boot

3 BIOS reports this event in the service processor’s system event log (SEL) as shown in the sample IPMItool output

There are what seems to be some suggested answers to include

  • Bad Caps
  • Bios verisons (happens in one version not the other)
  • Graphics card issues
  • Lack of power to the CPU

The list of possible generators seems to target everything but the computer case.

System Specs:

  • Windows Home Premium 64
  • Motherboard - MSI790FX-GD70 (MS7577) / Bios v 1.9 (American Megatrensa Inc)
  • Ram - Patriot G Series ‘Sector 5’ Edition 4GB DDR3 1600
  • CPU - AMD Phenom II X2 555 Black Edition Callisto 3.2GHz Socket AM3 80W (Note: unlocked 2 cores CPU Z ids it as phenom II x4 B55)
  • Graphics - 2 x Radeon 5750 in crossfire
  • PSU - ABS 900w
  • HDDs - 2 Seagate 1.5 TB Sata
  • SSD - 1 OCZ 120 GB Vertex Plus R2
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What OS are we running? What kind of hardware? do we have any actual error messages to look at? – Journeyman Geek Sep 27 '12 at 5:28
Updated info - The error was "A Hypertransport Sync Flood occurred on last boot". – Carl B Sep 27 '12 at 6:01
up vote 4 down vote accepted

A sync flood is initiated when the signals on the HT bus are in a state that makes normal operation impossible.

This could happen if the BIOS has configured the CPU/chipset incorrectly, but is most often the result of overclocking, flaky power, or broken hardware.

The mere fact that this happens does not help to find the cause. You should disable any kind of overclocking, and temporarily remove or replace all hardware components until you find the culprit.

share|improve this answer
+1 for you comment. That would explain why most of what I could find was on overclocer web sites. My only modifications where unlocking 2 of the 4 cores and adjusting ram timing to the advertised spec of 9-9-9-24 for two dimms of 2 GB ram. Nothing radical and all stable from initial testing after tweaks and for the past 2+ years. Although the Bios is set to auto on all other settings. – Carl B Sep 28 '12 at 12:22

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