Our next objective was to find out how the A-DATA PC 4000 modules are working in dual channel mode. For this test we selected the 2 modules with the highest overclocking headroom.
Table 2 shows that these 2 handpicked modules passed Memtest-86 up to 277 MHz. They completed the Sandra memory benchmark up to 281 MHz at 3-4-4-5 and 2.85 volt. Finally we had a look at the bandwidth using our ASUS P4P800-E sample because this board is known to have one of the best bandwidth outputs among 875P boards. At 200 MHz and running at CL 2.0-3-3-5 the P4P800-E produced a buffered bandwidth of 4900 MB/sec and an unbuffered bandwidth (SSE optimizations disabled) at around 2600 MB/sec. This is not very impressive and clearly the result of the “soft” memory timings. RAS to CAS (tRCD) and RAS Precharge (tRP) are driving bandwidth at 865/875 boards. In our tests, A-DATA 4000 allowed both parameters to run only at 3 clocks. This even when the memory was running at 200 MHz which is far below the advertised default frequency of 250 MHz. A-DATA PC 4000 makes a strong point though when it is running at high frequencies and in a particular of course when it is running at frequencies where other RAM modules would have given up much earlier. We finally arrived at around 3300 MB/sec unbuffered and almost 6800 MB/sec buffered bandwidth at 281 MHz. That is of course a mighty punch. Whether such high bandwidth is really necessary or beneficial for contemporary games and applications is another question. But it is certainly fun to run memory at such extreme frequencies.
250MHz buffered (left) and unbuffered (right)
270MHz buffered (left) and unbuffered (right)
281MHz buffered (left) and unbuffered (right)
SUMMARY AND CONCLUSIONS
A-DATA PC 4000 is delivering what the manufacturer is advertising and even more than this. All of the tested 12 modules 256 MB A-Data PC 4000 passed Memtest-86 at 268 MHz in dual channel mode. The best 4 modules passed Memtest-86 at 277 MHz. Almost all modules could complete the Sandra memory bandwidth benchmark at 280 MHz in single mode. At 250 MHz the tested modules did not need more than 2.55 volts. From 270 MHz onward it was necessary though to gradually increase the voltage to 2.85 volt.
On the negative side it has to be mentioned that the tested A-DATA PC 4000 modules did not run at low latency, “aggressive” timings. On none of our 3 test boards was it possible to run RAS to CAS (tRCD) and RAS Precharge (tRP) at 2 clocks even at only 200 MHz. The most aggressive memory timing set possible at the advertised frequency of 250 MHz was 2.5-4-3-5. At 200 MHz it was possible to run the modules at 2.0-3-3-5.
The combination of relative soft timings but extremely high frequency headroom makes A-DATA PC 4000 a good choice for users with a lower clocked “C” type Pentium 4 with a 200 MHz system bus. The low multipliers of a P4 2.4GHz or 2.6GHz allow to run this memory at extremely high frequencies, even with aircooled systems. On the other hand P4 3.0GHz and 3.2GHz owners will find this memory less useful: the x15 and x16 multipliers of these CPU will not allow them to fully exploit the frequency range of this memory. For them low latency PC 3200 or PC 3700 is probably a better choice than this A-DATA PC 4000.
We have the feeling that some of the tested A-DATA PC 4000 modules would run even higher than 281 MHz. Above 13 x 280 MHz = 3640 MHz our aircooled P4 2600 became unstable and most probably the bottleneck for further advancements. But we would not be surprised to see this PC 4000 memory running at up to 300 MHz with “vapochilled” (review here) P4 2.4GHz or 2.6GHz MHz CPUs. Another point to consider is the voltage. Almost all 865/975 boards provide a maximum of only 2.8 or 2.85 DIMM voltage. With modifications to the circuitry it is in many cases possible to get 0.1 or 0.2 volt more and that might further help to push the maximum frequency headroom of this memory towards 300 MHz.
Given the price of around 65~70 USD in Asia for the 256 MB module and 140 USD for the 512 M module A-DATA PC 4000 offers an excellent cost vs performance ratio.
All original content copyright James Rolfe.
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