Development of new memory standards has apparently stopped for now. Intel failed to convince users to rush to DDR3. No wonder -- there are few people, who wish to pay through their nose just for the sake of technical progress and get the same performance level (the problem is in the limited system bus on the Intel platform, which performs on a par with dual-channel DDR2-800 even with a FSB1600 processor, DDR2-1066 is out of the question). AMD platform is not limited in this way. However, the company plans to add DDR3 support to the memory controller (built into processors) only by the end of this year or in the beginning of the next year.
But the question is not only in CPU architecture. Most user applications, including professional ones, do not need larger memory bandwidth, and they cannot load all cores of quad-core processors. But does it mean that quad-core processors and higher memory bandwidths are currently expedient only for super computers and servers? That's not quite correct. Multi-core processors are installed into desktop computers primarily to make it more comfortable to work in a multitasking environment (they can really do that). Even if user applications do not operate with intense data flows, several of them started simultaneously significantly raise requirements to memory volume. As our objective is to assemble a "responsive" multitasking environment, the first idea that comes to mind is to eliminate HDD swapping.
4GB DDR2-1066 memory kits are actually offered for active users, who know why they need high memory volumes and how to minimize memory latencies. It's a very popular product now -- practically all manufacturers of memory modules rolled out such models. We'll examine memory modules from Apacer for a change. It's a well-known company in our parts, but its memory modules are less spread than flash memory, players, card readers, and other accessories.
Even though the name of this product mentions giants, heat spreaders on these modules make them higher only by one centimeter relative to the PCB level, lowly increase as far as products for overclockers are concerned. There are no extra accessories in the bundle. No fans -- fortunately, these modules do not need them.
The manufacturer's website does not explain how to decipher the DDR part number. The product description runs that density of Apacer DDR2-1066 memory modules varies from 512 MB to 2048 MB. They contain 8 FBGA chips. The PCB height is 1.18" (the total height with the heatspreaders is 4 cm). The manufacturer guarantees stable operation in the DDR2-1066 mode with the 5-5-5-15 timings at 2.2 V.
SPD data
General description of the SPD standard: JEDEC Standard No. 21-C, 4.1.2 - SERIAL PRESENCE DETECT STANDARD, General Standard.
Description of the DDR2 SPD standard: JEDEC Standard No. 21-C, 4.1.2.10 - Appendix X: Specific SPDs for DDR2 SDRAM (Revision 1.2).
| Parameter |
Byte |
Value |
Interpretation |
| 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 |
18h |
1.80 ns (555 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 |
08h |
8 |
| CAS Latency (CL) |
18 |
20h |
CL = 5 |
| Minimum clock cycle (tCK) at reduced CAS# latency (CL X-1) |
23 |
25h |
2.50 ns (400 MHz) |
| Minimum clock cycle (tCK) at reduced CAS# latency (CL X-2) |
25 |
30h |
3.00 ns (333 MHz) |
| Minimum Row Precharge Time (tRP) |
27 |
20h |
8.0 ns
4, CL = 5 |
| Minimum Row Active to Row Active delay (tRRD) |
28 |
6Ch |
27.0 ns
15, CL = 5 |
| Minimum RAS to CAS delay (tRCD) |
29 |
20h |
8.0 ns
4, CL = 5 |
| Minimum Active to Precharge Time (tRAS) |
30 |
1Bh |
27.0 ns
15, CL = 5 |
| Module Bank Density |
31 |
01h |
1024 MB |
| Write recovery time (tWR) |
36 |
3Ch |
15.0 ns
8, CL = 5 |
| Internal WRITE to READ command delay (tWTR) |
37 |
1Eh |
7.5 ns
4, CL = 5 |
| Internal READ to PRECHARGE command delay (tRTP) |
38 |
1Eh |
7.5 ns
4, CL = 5 |
| SDRAM Device Minimum Active to Active/Auto Refresh Time (tRC) |
41, 40 |
37h, 50h |
55.0 ns
31, CL = 5 |
| SDRAM Device Minimum Auto-Refresh to Active/Auto-Refresh Command Period (tRFC) |
42, 40 |
7Fh, 50h |
127.0 ns
71, CL = 5 |
| Maximum device cycle time (tCKmax) |
43 |
80h |
8.0 ns |
| SPD Revision |
62 |
12h |
Revision 1.2 |
| Manufacturer's JEDEC ID Code |
64-71 |
7Fh, 7Ah, 00h |
Apacer Technology |
| Module Part Number |
73-90 |
- |
78.AAGAL.9K4 |
| Module Manufacturing Date |
93-94 |
00h, 00h |
Not defined |
| Module Serial Number |
95-98 |
02h, 00h,
80h, 41h |
02008041 |
Some sensitive motherboards may freeze after reading SPD data from these modules. SPD supports a single CAS# value -- 5. But the mode that corresponds to this latency has nothing in common with the standard JEDEC mode. It even does not describe the recommended DDR2-1066 mode. It's DDR2-1100 mode (1.8 ns cycle time, 555 MHz) with 5-4-4-15 timings (integer). Owing to the multiplier for DDR2-1066 memory in Phenom processors, FSB frequency must be raised only to 208 MHz, even a processor with low overclocking potential can do that. Voltage level of 1.8 V is sufficient, so formally these modules can work in this mode (but it's not optimal). However, you will hardly find a motherboard to set its memory mode in this way. It will most likely choose DDR2-667 or 800 (as in our tests) and timings as it thinks fit (or it will fail to start up). Anyway, we cannot justify the lack of standard modes in SPD -- it's a must for modules to be detected and work out of the box on any motherboard. If a manufacturer guarantees modes with higher frequencies and wants to write them to the standard SPD area, it's possible to associate DDR2-800 or any other standard frequency with CL=4. In this case there will be no gripes with such modules.
On the other hand, SPD specifies manufacturer's ID code. Serial and Part Numbers of the module are specified, and they almost match those on the sticker (Serial Number is not encoded completely, but even the standard SPD allows only 4 bytes).
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