Maximizing Integrated Graphics: Data Rate Or Latency?

With data rates topping 6 GT/s on buses up to 384-bits wide, high-end graphics cards are hardly starved for memory bandwidth. Integrated engines, on the other hand, are still limited to a 128-bit aggregate pathway through two 64-bit channels. And then there are the lower data rates of DDR3 DIMMS versus GDDR5 packages. But throughput isn't the biggest issue those built-in GPUs face. They're necessarily a lot less complex, since they share die space with host processing resources. And then there's the matter of memory latency...

If we look back to when DDR2-533 CAS 3 was the way to go for exceptionally low latency, we saw a few enthusiasts trying to push those same modules down to CAS 2. These days, we see DDR3-1600 CAS 7 as a real possibility, and most tuners are having similar trouble pushing that memory to CAS 6. Even at DDR3-2133, we’re trying to hit CAS 8 when only CAS 9 appears achievable. Lo and behold, when we divide 2133 by eight, 1600 by six and 533.3 by two, we always get 266.6. Divide by two to get the bus frequency and invert the number to get cycle time, and what we’ve really been fighting for the past nine years is a memory turnaround time of 7.5 nanoseconds.

Still unable to reliably break past the 7.5 ns latency barrier, today’s performance search primarily focuses on data rates. We’ll still compare these six contenders to JEDEC-standard DDR3-1600 CAS 11 specs though. Here are each kit's specifications.

Brand/Model Rated MT/s Rated CL Rated Volts Price Adata XPG V2 AX3U2400W8G11-DMV DDR3-2400 11-13-13-35 1.65 V $184 AMD Gamer Series AG316G2130U2K DDR3-2133 10-11-11-30 1.65 V $176 Crucial Ballistix Tactical BLT2KIT8G3D1869DT1TX0 DDR3-1866 9-9-9-27 1.50 V $153 G.Skill DDR3-1866 C10 F3-14900CL10D-16GBXL DDR3-1866 10-11-11-30 1.50 V $135 Mushkin Redline Ridgeback 997121R DDR3-2133 9-11-11-28 1.65 V $180 Patriot Viper 3 PV316G240C0KRD DDR3-2400 10-12-12-31 1.65 V $195

We chose JEDEC-standard DDR3-1600 as a starting point because we believe that anyone seriously interested in gaming on a platform with integrated graphics shouldn’t settle for less. We found a 16 GB dual-channel pair of those for $110.