Articles: Memory

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Finding Maximum Frequencies

We are going to test the performance of Kingston HyperX DDR3-1866 memory kit on the following testbed:

  • Mainboard: Gigabyte GA-EX58-Extreme, rev. 1.0, BIOS F4;
  • CPU: Intel Core i7-920 (2.66GHz, 133MHz base frequency, 8MB L3 cache, Bloomfield, rev. C0, 1.225V Vcore);
  • Memory: 3 x 1024MB DDR3 Kingston HyperX DDR3-1866, KHX14900D3T1K3/3GX, (1866MHz, 9-9-9-27, 1.65V voltage);
  • Graphics card: ATI Radeon HD 4870 512MB (RV770, 750/750/3600 MHz, 800 SP, 40 TMU, 16 ROP, 256-bit 512MB GDDR5);
  • HDD: Samsung SP2504C (250GB, SATA II, 7200RPM, 8MB, rev.A);
  • CPU cooler: Cooler Master GeminII (120mm Protechnic Electric MGA12012HB-O25 fan, 1500-2500RPM);
  • Thermal interface: Noctua;
  • PSU: Antec NeoPower Neo HE 550 rev. A4 (550W);
  • System case: Antec Skeleton.

In the default mode Gigabyte GA-EX58-Extreme mainboard, like other Intel X58 Express based boards, sets the memory frequency at 533MHz, i.e. works with the memory as DDR3-1067. The timings in this case are set at 9-9-9-24-1T. The board supports Intel XMP technology that is why it adjusts the DDR3 settings above the nominal for the regular DDR3 SDRAM but to the standard values for Kingston HyperX DDR3-1866 once you select the first profile in the mainboard BIOS.

If you choose the second profile, the board starts acting in a very interesting way. This profile has the memory working at 900MHz, i.e. as DDR3-1800. In this case the board lowers the processor clock frequency multiplier from x20 to x17, but raises the base frequency from 133MHz to 150MHz. As a result, the CPU frequency is 2.55GHz, which is as close at it can get to the nominal 2.66GHz. The memory, however, works exactly at 900MHz, i.e. as DDR3-1800.

In both cases the board increases the memory voltage to 1.65V. However, I was a little confused to see that the QPI bus voltage rose to 1.5V in the first case and to 1.45V in the second, which is still way too much. I have to remind you at this point that the default QPI/VTT Voltage is only 1.175V.

I failed to get the system to start at 933MHz memory frequency after only raising the voltage to 1.65V. The board would boot but hang right during POST when it got to the memory part. Then I increased the QPI/VTT Voltage to 1.335V. I chose this number almost randomly: the next available setting of 1.355V was already considered dangerously high and was highlighted purple in the mainboard BIOS. It was a perfect guess: the system remained stable at this QPI/VTT Voltage and passed all tests, but we couldn’t set this parameter any lower than that. We needed to get to the lowest QPI/VTT Voltage setting possible, because the higher you set it, the more it increases the processor temperature. You can barely notice it in the nominal mode, but during overclocking the temperature may rise dangerously high.

As a result, we tested our Kingston HyperX DDR3-1866 memory modules at the voltage increased to 1.65V and QPI/VTT Voltage set at 1.335V. We used System Stability Tester utility calculating 2-8 million digits of Pi in multi-threaded mode. The system was considered stable if it could also pass a 1-hour Prime95 test in Blend mode. Unfortunately, we couldn’t increase the frequency beyond the nominal 933MHz at 9-9-9-24 timings. This is pretty strange because memory doesn’t usually work at the maximum of its capacity, just like other system components. However, it could be the Gigabyte GA-EX58-Extreme mainboard that we used. We are going to repeat our tests on a different mainboard shortly and will let you know what we find.

Memory modules SPD states that at CAS Latency of 8 the memory can work at 829MHz frequency as DDR3-1658. In reality our memory kit did much better and passed the tests at 906MHz, i.e. in DDR3-1812 mode. It should work at 725MHz (DDR3-1450) at CAS Latency 7, but in fact it worked as DDR3-1530. As for the CAS Latency 6 at 1.65V voltage there is no info about it in the memory modules SPD. All we know is that the frequency will be at least 444MHz at 1.5V voltage setting. The kit passed all tests at 695MHz, i.e. in DDR3-1390 mode.

The results are overall very good, especially keeping in mind that they were obtained I triple-channel mode and at a relatively low voltage setting of 1.65V. However, these are only preliminary data that were obtained in easy conditions with little or no CPU overclocking, i.e. in nominal processor mode. We used the following combinations of base and memory frequencies: 133/1867 MHz with 9-9-9-24 timings, 151/1812 MHz (8-8-8-22), 153/1530 MHz (7-7-7-20), and 139/1390 MHz (6-6-6-18). I wonder if we can get the same results during actual system overclocking.

I have first used Intel Core i7-920 processor during the tests of Gigabyte GA-EX58-UD5 and GA-EX58-Extreme mainboards. It could overclock up to 181MHz base frequency at its nominal .225V Vcore, i.e. with all power-saving technologies up and running. With the Vcore increased to 1.3V, it remained stable at 188MHz. In both cases the memory worked at its maximum possible frequency of 1067MHz and 1128MHz respectively. We also managed to lower the timings to 6-6-6-18, which is pretty aggressive for DDR3.

When we overclock our CPU to 181MHz base frequency, we can set the memory frequency at 1810MHz – the closest value to the nominal 1867MHz. The obtained results suggest that we can even lower the timings to 8-8-8-22 in this case. Although this frequency is dangerously close to 1812MHz, which is the maximum frequency for the memory to remain stable with these timings, the system passed the stability tests successfully. We just had to change the Performance Enhance parameter in the mainboard BIOS from Turbo to Standard.

When the CPU is overclocked to the maximum of 188MHz base frequency, you can set the memory speed at 1880MHz, however, this value is outside the interval supported by Kingston HyperX DDR3-1866. We did try to conquer this frequency by raising the voltage, but it led to CPU temperature increase beyond 90°C, instead of system stability. To ensure that the memory would work at its absolute maximum frequency, maybe even at the expense of the resulting CPU frequency, we lowered the base frequency to 186MHz. The memory frequency in this case equaled 1860MHz, but even in this case the system remained unstable.

As a result, we had to set the memory frequency one step lower to 1504MHz. Theoretically, you could lower the memory timings to 7-7-7-20 in this case, which we did. By the way, even in this case when we set the processor Vcore to 1.3V, enabled Load-Line Calibration technology and set QPI/VTT Voltage to 1.335V the maximum CPU temperature was 88°C after one-hour run of Prime95 test. It is too high for a high-end Cooler Master GeminII cooler with a 120-mm fan working at 2500RPM and a system assembled in and open Antec Skeleton system case.

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