Next: OCNG5: Installation
OCNG5 (OC Next-Generation, version 5) is a firmware modification for most Supermicro G34 motherboards (complete list of supported motherboards below) that allows overclocking of all current AMD Opteron processors, that is 6100, 6200 and 6300 series.
OCNG5 works by altering motherboard's reference clock early at boot and tuning processor components for performance and stability.
Reference clock (referred to as BCLK in Intel processors) is used to derive a number of system clocks (including core clock, integrated northbridge clock, hypertransport clock and memory clock). Thus, in principle, increasing reference clock increases system speed.
Special care must be taken when increasing reference clock as certain components and interfaces don't operate well beyond their rated speeds. Specifically, DRAM modules may not be able to handle increased memory clock and memory interface tuning may not be possible for very high speeds (given lack of characterization data). Similar limitation applies to hypertransport interface.
OCNG5 takes care of these risks by ensuring that rated memory and hypertransport speeds are never exceeded.
Taking advantage of performance/enthusiast memory is, however, possible. OCNG5 fully supports XMP profile 1 and automatically uses it (if available) whenever OCNG5 features are enabled.
OCNG5 can currently be configured from Windows and Linux. Once configured, any operating system can be booted and take advantage of improved performance.
As overclocking translates to increased power draw, one needs to pay special attention to cooling the system (both, the motherboard and the processors). On one hand, additional heat limits attainable speeds and affects quality of voltage regulation. On the other, overheating power delivery circuits may lead to their destruction and render the motherboard inoperable. These make two good reasons to make sure that heat is transported away from your system.
Caring for power delivery circuits is especially important when using high power parts (carrying 140W TDP, including 6176 SE, 6282 SE, 6284 SE, 6386 SE). When using high power parts or whenever AC power (80% eff. assumed) starts to exceed 200W per installed CPU, providing airflow across the motherboard (front-to-back) is a must. Similarly, as PCB itself acts as a radiator, providing airflow underneath the motherboard is very important as well.
This is especially true for systems located in enthusiast cases or on open trays. Server cooling systems typically accommodate this recommendation so no special action (except, say, bumping fan speeds) is required.
OCNG5 also comes with a safety mechanism: if the board doesn't POST three times in a row, stock settings are restored. This eliminates the need to reset CMOS (a time-consuming process) during OC process.
As of today, OCNG5 supports following motherboards:
- H8QGL-6F (*)
- H8QGL-6F+ (*)
- H8QGL-iF (*)
- H8QGL-iF+ (*)
(*) incompatibility between OCNG5 and IPMI has been identified
on H8QGL series boards (no boot when overclocked);
if IPMI is not required, disabling IPMI (using jumper JPB1) is
otherwise, the issue can be worked around by completely removing
JPB1 jumper; doing so will still allow IPMI/KVM access but IPMI access
from the OS will not be possible
Certain dual-socket G34 boards (H8DGU, H8DGT, H8DGG, etc.) are currently unsupported.
Next: OCNG5: Installation