Comparing Memory Bandwidth: UNBuffered Memory Performance

In our article,, we demonstrated that the UNBuffered SiSoft Sandra Memory Test correlated very well with MemTest86 bandwidth results. With all of the Buffering techniques disabled, scores arelower — sometimes a 50% drop — than the scores you are accustomed to seeing for Sandra Memory tests. However, the unbuffered scores have proven to be a very sensitive measure of memory bandwidth. Regarding memory performance, we will be looking at the maximum stable overclock for the memory and the SiSoft Sandra UNBuffered Memory Test.The idea of the UNBuffered Memory Benchmark is very simple — you merely turn off all memory buffering techniques. Sandra makes this very easy to do. Select 'Memory Benchmark', right-click 'Module Options', and uncheck the nine boxes that are related to buffering.

Crucial DDR333 Samsung SS Performance

Intel 875 Chipset, Dual-Channel, Maximum Overclock DDR Memory Speed Memory Timings Memory Voltage

(vDIMM) UNBuffered

Sandra 2003 Memory Test

(MB/Second) 450 Maximum SPD

2.5-7-4-4 2.7V 2472 INT

2460 FLT 460 3-8-4-4 2.8V 2436 INT

2527 FLT

Lasering for Heat Dissipation

Please keep in mind that the Crucial DDR333 modules using Samsung memory are single-sided DIMMs. As we illustrated in, the performance of two SS modules is lower than the performance of two DS modules in 875/865 boards, and cannot be directly compared.All memory tests were run on an Abit IC7, Intel 875 Canterwood motherboard with BIOS revision 1.5, and a 2.4C Pentium 4, 800FSB processor that has reached 290MHz (1160FSB) on this motherboard.Given the ability of this Samsung memory, rated at DDR333 or DDR400, to reach DDR460 at 2.8V, we can fully understand why OCZ chose this as their base memory chip. However, as good as this performance is, it does not match the specified performance of OCZ 3700 GOLD of DDR466, 2.5-7-3-3, at 2.65V. So how does a manufacturer of high-speed memory get from this base performance to the performance of 3700 GOLD?When information about OCZ using Samsung TCB3 chips for 3700 GOLD first appeared, others were asking the same question we were asking: how did OCZ get a memory rated at DDR333/400 to the performance levels of 3700 GOLD — or did they?All memory manufacturers (as well as CPU and chipset manufacturers) "bin" chips. This means that they sort chips by speed capabilities. The top-performing chips are then used in the highest-speed products — the rest going into lower rated products. OCZ explained that, in addition to speed binning, they laser the chips to improve heat dissipation before sorting, using the best chips for OCZ 3700 GOLD. They also released an internal document describing the lasering process and how it improves heat dissipation. The information below is from the released internal document:"INTERNAL USE ONLY : ENGINEERING DEPT -TW-CAThermal modification of standard DDR DRAM TSOP packages , for increased thermal dissipation and speed reclassification.Note #1 : Reference EL DDR packing specification is linked at /spec/elddr.htmlPurpose : Increase speed of ( SEC packaged ) TSOP , through using EL DDR packaging theory. To fill product shortage during die revision changeEL DDR Packaging : by decreasing the thickness of encapsulate (low thermal transfer rate ) we are able to effectively increase heat dissipation in DRAM and thereby increase the effective speed of each IC . Using a third party fabrication and packaging plant this theory has been proven and the (B) die revision OCZ EL DDR die had great success. Average maximum speed increase during stage 2 testing has been verified over 23 MHz.Proposition: While dies fabricated by 3rd parties for OCZ in 3rd party packaging have proven successful to this point . We feel that to insure our success we should supplement by speed binning large quantities of 3rd party IC's and by physically modifying the package decreased thermal resistance and re-speed grade the ICs using the standard Advantest ATE.Industry Disclosure: See Ryan PetersenProcess Engineering : See XXXXXXXXXProcess Overview :Samsung semi will provide die location information , we will be using the DP-7 CO 2 laser to remove the surface material from the package face only average laser cut depth is 7mill . After surface removal the package should be sent to ISE for environmental test and then re-speed graded after speed grade and classification chips will be marked ( standard process) and standard process thereafter."