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Memory Module Analysis. Part 21: Kingston HyperX DDR2-800 (PC2-6400)

May 19, 2006



We proceed with the low-level analysis of the most important characteristics of high-performance DDR2 memory modules using our RightMark Memory Analyzer. We have recently reviewed a dual-channel kit of Kingston high-end memory modules from the HyperX series, designed for the nonstandard DDR2-900 mode. And today we are going to review a similar offer, which still complies with the JEDEC standard — a dual-channel kit of high-capacity (2GB in total) Kingston HyperX DDR2-800 memory modules, which offers low latencies (according to the manufacturer.)

Manufacturer Information

Module manufacturer: Kingston Technology
Manufacturer of module chips: Elpida Memory, Inc.
Web site of the module manufacturer:
http://www.kingston.com/hyperx/products/khx_ddr2.asp
Web site of the chip manufacturer:
http://www.elpida.com/en/products/ddr2.html

Module Exterior

Photo of the memory module

With heatsinks removed:

Photo of the memory chip

Module Part Number

Module Part Number Expansion

The manufacturer's web site does not publish the DDR2 Part Number expansion. Datasheet on the modules with Part Number KHX6400D2LLK2/2G runs that this product is a kit of two modules with low latencies (hence the "LL" abbreviation), 1GB each, 128M x 64 configuration, based on sixteen 64M x8 chips. The manufacturer guarantees 100% stable operation in the standard DDR2-800 mode with 4-4-4-12 timings and 2.0 V voltage. But the default mode written in the SPD chip is DDR2-800 with 5-5-5-15 timings and the voltage of 1.8 V.

Chip Part Number Expansion

Like in the previously reviewed Kingston HyperX DDR2-900, these memory modules use chips with the original designation of their real manufacturer (Elpida). So we can examine their characteristics and study the data sheet on 512-Mbit DDR2 Elpida memory chips, used in these modules.

Field Value Expansion
0 Manufacturer (n/a, "E" = Elpida Memory)
1 Type (n/a, "D" = monolithic device)
2 E Product family: "E" = DDR2
3 51 Capacity/Logical Banks: "51" = 512/4 banks
4 08 Organization: "08" = x8
5 A Power supply, Interface: "A" = SSTL 1.8V
6 G Die revision: "G"
7 Package code (n/a, "SE" = FBGA)
8 6E Speed: "6E" = DDR2-667 (5-5-5)
9 E Environment code: "E" = Lead free

As usual, designation of these Elpida chips lacks fields for the manufacturer (Elpida Memory), device type (monolithic), as well as package code (FBGA). As you can see on the table, the module chips are of the 64M x8 setup (full capacity — 512 Mbit). They are designed for the slow DDR2-667 mode (5-5-5 timings), which corresponds to the first revision of the DDR2-667 standard. Note that the same chips (but from the other manufacturer) are used in higher-speed Kingston HyperX DDR2-900 modules, which we already reviewed. To all appearances, we can speak of thorough selection of DDR2-667 chips by the manufacturer to get the highest-speed and the most reliable samples, instead of using real DDR2-800 chips.

SPD chip data

Description of the general SPD standard:

Description of the specific SPD standard for DDR2:

Parameter Byte Value Expansion
Fundamental Memory Type 2 08h DDR2 SDRAM
Number of Row Addresses on this assembly 3 0Eh 14 (RA0-RA13)
Number of Column Addresses on this assembly 4 0Ah 10 (CA0-CA9)
Number of DIMM Banks 5 61h 2 physical banks
Data Width of this assembly 6 40h 64 bit
Voltage Interface Level of this assembly 8 05h SSTL 1.8V
SDRAM Cycle time (tCK) at maximum supported CAS# latency (CL X) 9 25h 2.50 ns (400.0 MHz)
DIMM configuration type 11 00h Non-ECC
Refresh Rate/Type 12 82h 7.8125 ms — 0.5x reduced self-refresh
Primary SDRAM Width (organization type) of the memory module chips 13 08h x8
Error Checking SDRAM Width (organization type) of the memory chips in the ECC module 14 00h Not defined
Burst Lengths Supported (BL) 16 0Ch BL = 4, 8
Number of Banks on SDRAM Device 17 04h 4
CAS Latency (CL) 18 38h CL = 5, 4, 3
Minimum clock cycle (tCK) at reduced CAS# latency (CL X-1) 23 3Dh 3.75 ns (266.7 MHz)
Minimum clock cycle (tCK) at reduced CAS# latency (CL X-2) 25 50h 5.00 ns (200.0 MHz)
Minimum Row Precharge Time (tRP) 27 32h 12.5 ns
5.0, CL = 5
3.3, CL = 4
2.5, CL = 3
Minimum Row Active to Row Active delay (tRRD) 28 1Eh 7.5 ns
3.0, CL = 5
2.0, CL = 4
1.5, CL = 3
Minimum RAS to CAS delay (tRCD) 29 32h 12.5 ns
5.0, CL = 5
3.3, CL = 4
2.5, CL = 3
Minimum Active to Precharge Time (tRAS) 30 27h 39.0 ns
15.6, CL = 5
10.4, CL = 4
7.8, CL = 3
Module Bank Density 31 80h 512 MB
Write recovery time (tWR) 36 3Ch 15.0 ns
6, CL = 5
4, CL = 4
3, CL = 3
Internal write to read command delay (tWTR) 37 1Eh 7.5 ns
3.0, CL = 5
2.0, CL = 4
1.5, CL = 3
Internal read to precharge command delay (tRTP) 38 1Eh 7.5 ns
3.0, CL = 5
2.0, CL = 4
1.5, CL = 3
SDRAM Device Minimum Active to Active/Auto Refresh Time (tRC) 41, 40 33h, 30h 51.5 ns
20.6, CL = 5
13.7, CL = 4
10.3, CL = 3
SDRAM Device Minimum Auto-Refresh to Active/Auto-Refresh Command Period (tRFC) 42, 40 69h, 30h 105.0 ns
42, CL = 5
28, CL = 4
21, CL = 3
Maximum device cycle time (tCKmax) 43 80h 8.0 ns
SPD Revision 62 12h Revision 1.2
Checksum for Bytes 0-62 63 31h 49 (true)
Manufacturer’s JEDEC ID Code 64-71 7Fh, 98h Kingston
Module Part Number 73-90 00h...00h Not defined
Module Manufacturing Date 93-94 06h, 0Fh Year 2006, Week 15
Module Serial Number 95-98 5Ah, 15h,
8Eh, 29h
298E155Ah

SPD data are not standard, probably due to the low latency design. Three different CAS# latencies are supported — 5, 4, and 3. The first value (CL X = 5) corresponds to DDR2-800 (2.5ns cycle time) and 5-5-5-15.6 timings (rounded up to 5-5-5-16), which approximately matches the official values, published in the documentation (5-5-5-15, DDR2-800). Strange as it may seem, the second tCL value (CL X-1 = 4) corresponds to DDR2-533 (3.75ns cycle time), not to DDR2-667. The timing scheme for this case is not composed of integer values - it can be written as 4-3.3-3.3.-10.4, to be rounded up to 4-4-4-11. And finally the third value of CAS# latency (CL X-2 = 3) corresponds to DDR2-400, again with a fractional timings scheme (3-2.5-2.5-7.8) to be rounded up to 3-3-3-8. The module features a relatively high minimum refresh to active/refresh command period tRFC = 105.0 ns, which we come across rather often in high-speed modules. SPD revision, Manufacturer’s JEDEC ID Code, Manufacturing Date and Serial Number of the module are correct. But there is no data on the module's Part Number.

Testbed configuration

  • CPU: Intel Pentium 4 Extreme Edition 3.73 GHz (Prescott N0, 2 MB L2)
  • Chipset: Intel 975X
  • Motherboard: ASUS P5WD2-E Premium, BIOS 0404 dated 03/22/2006
  • Memory: 2x1024 MB Kingston HyperX DDR2-800 Low Latency

Test Results

Performance tests

In the first series of tests we used the timing scheme, set in BIOS Setup by default (Memory Timings: "by SPD"). The modules were tested in two modes — DDR2-667 with 200 MHz and 266 MHz FSB (memory multipliers - 1.67 and 1.25 correspondingly) and DDR2-800 with 200 MHz and 266 MHz FSB (memory multipliers - 2.0 and 1.5 correspondingly). We remind you that from our previous review on, we upgrade to RMMA 3.65 with a larger memory block to be tested (32MB) by default, which greatly reduces the effect of a relatively large 2MB L2 Cache in Pentium 4 Extreme Edition processors.

In DDR2-667 mode, the motherboard's BIOS set the timings to 5-5-5-13 by default ("at random", as the SPD chip lacks the data necessary), while the default timings in DDR2-800 mode were 5-5-5-16 (by SPD).

Parameter / Mode DDR2-667 DDR2-800
FSB Clock, MHz 200 266 200 266
Timings 5-5-5-13 5-5-5-13 5-5-5-16 5-5-5-16
Average memory read bandwidth, MB/sec 5387 6406 5617 6875
Average memory write bandwidth, MB/sec 2056 2252 2321 2465
Max. memory read bandwidth, MB/sec 6491 8232 6528 8541
Max. memory write bandwidth, MB/sec 4282 5660 4279 5679
Minimum Pseudo-Random Access Latency, ns 56.6 50.0 52.5 45.5
Maximum Pseudo-Random Access Latency, ns 66.2 57.3 61.7 53.0
Minimum Random Access Latency*, ns 118.8 105.3 106.0 95.4
Maximum Random Access Latency*, ns 143.8 123.9 130.2 115.5
Minimum Pseudo-Random Access Latency, ns
(without hardware prefetch)
87.0 78.2 80.3 70.4
Maximum Pseudo-Random Access Latency, ns
(without hardware prefetch)
113.7 96.5 107.3 90.1
Minimum Random Access Latency*, ns
(without hardware prefetch)
119.6 105.5 106.2 95.9
Maximum Random Access Latency*, ns
(without hardware prefetch)
145.5 125.0 133.7 116.6

*32 MB block size

Performance results of these modules are quite high — maximum real memory bandwidth is approximately 6.4-6.5 GB/s with 200-MHz FSB and 8.2-8.6 GB/s with 266-MHz FSB, that is it practically reaches the theoretical maximum in FSB bandwidth (it's even slightly higher due to the effect of L2 Cache in a processor). As usual, memory access latencies are decreased in faster modes (when you go from DDR2-667 to DDR2-800) as well as with higher-clocked FSB (when you go from 200-MHz to 266-MHz FSB). Minimum memory latency in DDR2-800 with 266 MHz FSB is from 45.5 ns (pseudo-random walks, enabled hardware prefetch) to 116.6 ns (random walks, disabled hardware prefetch), which is a tad worse than the results of higher-ranked Kingston HyperX DDR2-900 modules.

Stability tests

Timing values, except for tCL, were adjusted "on the fly" due to the built-in RMMA feature that allows to change dynamically memory settings supported by the chipset. Memory operating stability was evaluated with an auxiliary utility RightMark Memory Stability Test, included into RMMA.

Parameter / Mode DDR2-667 DDR2-800
FSB Clock, MHz 200 266 200 266
Timings 3-4-4
(2.0 V)
3-4-4
(2.0 V)
4-5-4-12
(2.0 V)
4-5-4-12
(2.0 V)
Average memory read bandwidth, MB/sec 5537 6798 5652 6990
Average memory write bandwidth, MB/sec 2260 2465 2358 2613
Max. memory read bandwidth, MB/sec 6501 8331 6515 8632
Max. memory write bandwidth, MB/sec 4282 5664 4281 5675
Minimum Pseudo-Random Access Latency, ns 53.1 46.1 49.3 44.4
Maximum Pseudo-Random Access Latency, ns 62.5 53.3 59.0 51.8
Minimum Random Access Latency*, ns 109.6 95.4 105.5 92.7
Maximum Random Access Latency*, ns 133.9 114.9 129.7 112.7
Minimum Pseudo-Random Access Latency, ns
(without hardware prefetch)
81.9 70.9 75.2 68.5
Maximum Pseudo-Random Access Latency, ns
(without hardware prefetch)
107.9 93.2 102.0 88.4
Minimum Random Access Latency*, ns
(without hardware prefetch)
110.4 95.9 105.8 93.1
Maximum Random Access Latency*, ns
(without hardware prefetch)
136.6 116.7 132.6 113.6

*32 MB block size

Strange as it may seem, the minimum timings, we managed to obtain in DDR2-667 mode with the recommended increased voltage of 2.0 V, look quite unassuming - 3-4-4 (tRAS is ignored in this case.) By the way, we managed to set much better timings (3-3-2) for Kingston HyperX DDR2-900 under these conditions. The situation in DDR2-800 is still worse — minimum timings possible (stable) were only 4-5-4-12, even higher than the official 4-4-4-12 scheme. Interestingly, tRAS makes a determining contribution to memory stability in this case — its reduction results in an immediate system freeze.

As usual, "extreme" timings only insignificantly increase memory bandwidth, the effect is noticeable only in random access latencies. Maximum effect of reduced latencies is reached in DDR2-667 - about 9 ns, that is approximately 8%.

Bottom line

High-capacity Kingston HyperX DDR2-800 modules (PC2-6400) with "low latencies" can operate in DDR2-667 and DDR2-800 modes in nominal conditions (that is with standard timings, like 5-5-5-15 for DDR2-800) and are characterized by high performance in these modes. At the same time, the overclocking potential of these modules as far as timings are concerned leaves much to be desired. So we can hardly refer to them as "Low Latency" modules. The minimum timings possible in DDR2-667 mode that do not damage memory operation stability are just 3-4-4 (with the recommended voltage of 2.0V). What concerns DDR2-800 — 4-5-4-12, which is even worse than 4-4-4-12, official values published in the documentation. At least on the ASUS P5WD2-E motherboard (we use it in our tests), which proved itself a trustworthy model for testing high-speed DDR2 memory modules.



Dmitri Besedin (dmitri_b@ixbt.com)
May 19, 2006

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