Ddr2 high density: Low or High Density? – gr33nonline

Low or High Density? – gr33nonline

Preamble

I need some (4 x 4 GB) memory DDR2-800 (or DDR-667) PC2-6400u (or PC2-5300) UDIMMS Unbuffered Non-EEC for an AMD Althon Dual Core 4850e motherboard.

From DDR2 PC2-6400U 800Mhz, high density are not recommended.

If you google a particular memory stick identifier, you can end up with different looking sticks (126 or 32 ICs)

So how to tell low density from high density?

Apparently sticks which have 16 chips on each side are low density, and those with just 16 total (8 each side) are high density (Source: Special high density AMD compatible DDR2 RAM?). The high density RAM can be a bit hit or miss, more often miss.

However, this guy says it is OK, RAM upgrades: Watch for high- and low-density requirements, although he does seem to be mixing memory sizes up (both boards have 16 chips, but on set is larger than the other), rather than comparing like size memory capacity sticks. See description of 32 chip stick below.

Don’t mix densities, Low density vs high density

Identifying the Samsung ram module help . This guy has some 32 IC memory labeled at the 16 IC memory, see below.

Comparisons

High Density: From Samsung 16GB 4x 4GB PC2-6400 DDR2 DIMM High Density Memory Only For AMD Chipest

High density 4 GB memory

Serial: M395T5160QZ4-CF7

I actually checked with the vendor, and there is indeed only 16 ICs on the stick, so this would appear to be a fake, or wrongly labelled, as should have 32 ICs, see Conflicting images below

Low density (supposedly, although the item description states otherwise): From Samsung 4GB 8GB 16GB DDR2 800MHz PC2-6400 240PIN DIMM AMD Desktop Memory Ram LOT

Low density 4 GB memory

Serial: M378T5263AZ3-CF7

Interestingly this item’s description states (verbatim from a link above):

Difference of this item

• All high density 1GB modules are made with 16 chips (8 chips on each side) using 128MX4 device.
• All low density 1GB modules are made with 16 chips (8 chips on each side) using 64MX8 device.
• The item is high density and it can not work in any intel cpu  motherboard.It only support AMD chipset motherboard.
• Not work with All DELL,IBM,Apple,HP,Compaq,Gateway,Acer.Lenovo,Emachines,Packbell Computers.

Packing List

4GB PC2-6400 desktop memory ram  x 1/2/4/10

Conflicting images

This site, M395T5160QZ4-CF7 Samsung 4GB DDR2 Fully Buffered FB ECC PC2-6400 800Mhz 2Rx4 Memory, states that M395T5160QZ4-CF7 is fully buffered and EEC – but shows it as a 32 IC stick, not 16 as shown above. Other sites show the same:

M378T5263AZ3-CF7 Samsung 4GB PC2-6400 DDR2-800MHz non-ECC Unbuffered CL6 240-Pin DIMM Dual Rank Memory Module, states the M378T5263AZ3-CF7 is unbuffered non-EEC. Again a 32 IC stick is shown

This site, M378T5263AZ3-CF7 – Samsung 4GB DDR2-800MHz PC2-6400 non-ECC Unbuffered CL6 240-Pin DIMM Dual Rank Memory Module shows a 16 IC stick, as does Samsung M378T5263AZ3-CF7 PC2-6400U-666 4GB 2Rx8 800MHz 240-pin DIMM, Non-ECC DDR2 Desktop Memory Full Technical Specs and Reviews – although in both cases, a generic stick is shown.

Fakes

This link, Spot the Fakes, is interesting and shows the infamous 32 IC stick above as the fake:

Second from bottom is infamous “amd-only” memory
made from high density chips salvaged from registered modules.
While it’s fake it usually works fine with AMD cpus.

Conclusion

Whilst the comparison of the number of ICs between like capacity memory sticks seems a valid definition of low and high density, the best answer seems to be from How to identify if a module is LOW or HIGH density?

Density is related to the amount or capacity of memory locations on memory chips (memory depth (memory locations per bank x number of banks) x data width).

To determine density (and compatibility) requires additional information from memory manufacturers ie memory chip depth (locations/bank x banks) and data width be added to memory specifications. Unfortunately most memory manufacturers do not provide this information (yet).

I have contacted several memory manufacturers so far (directly or via forums) to request that memory chip configuration details be added to memory specifications to enable a better idea of memory density and compatibility.

Amount of Density is relative, with respect to the two memory modules being compared.

Examples –

1) One module uses 256 Mb chips, while another module uses 512 Mb chips. The Low Density memory here would be the module with the 256 Mb chips, and the High Density memory would be the module with the 512 Mb chips.

2) One module uses 1 Gb chips, while another module uses 2 Gb chips. The Low Density memory here would be the module with the 1 Gb chips, and the High Density memory would be the module with the 2 Gb chips.

So, it would be preferable to list the actual memory chip configuration (memory depth x data width x number of chips used on module) instead of trying to determine which chips are High Density and which chips are Low Density.

…

The terms High Density and Low Density relating to memory are arbitrary/subjective, there is no “rule” as such to say whether memory is either High or Low Density. It is up to the individual to decide what is what. Dell or whoever have just applied their judgement as to what is High and what is Low Density memory. Their interpretation may not match other peoples’ interpretation.

It is the actual chip configuration which aids in determining compatibility and not the arbitrary terms High and Low Density. One might say a module using 512 Mb chips is High Density, but another might label it as being Low Density; that is not useful for other people. This is therefore too subjective, and open to misinterpretation.

Dell (and whoever else) should have instead referred to chip configuration details instead of using the terms Low and High Density memory, since they did not specify what their interpretation of High and Low Density memory is/was.

Because of this subjectivity, it is better to have chip configuration details made available instead. This information is factual and there can be no misinterpretation.

Final purchase

In the end cost bore out, and I ended up getting the £20.96, Samsung 4GB 8GB 16GB DDR2 800MHz PC2-6400 240PIN DIMM AMD Desktop Memory Ram LOT, due to the 32 ICs and the serial number, which if correct, would give unbuffered, non-EEC memory. We shall see how it pans out.

The memory arrived:

and the memory works well:

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DDR2 4GB DIMMs | OS/2 Museum

Last week the OS/2 Museum got its first ever set of real (i.e. not fake) 4 GB DDR2 desktop (unbuffered) DIMMs, a pair of Samsung 4GB PC2-6400U modules. Such modules are quite rare and correspondingly tend to be unavailable at a reasonable price. Moreover there is a lot of fake “AMD only” modules. But why are the real DDR2 4 GB UDIMMs so rare?

The short answer is “because they’re almost useless”.

The long answer is that DDR2 modules based on 2 Gbit memory technology became available too late in the DDR2 life cycle, which led to such modules being rather poorly supported. They are not unsupported—there are DDR2 boards which not only accidentally happen to work with such modules but where the manufacturers officially support them.

A case in point is the Intel DQ45CB board. It came out in mid-2008 and when it was released, it did not list 4 GB modules as supported, most likely because they weren’t available. The board has four memory slots and it was initially specified to support up to 8 GB memory maximum (with four 2 GB modules). Sometime between April 2009 (specification update E53961-004US) and May 2010 (specification update E53961-006US), Intel officially changed the board’s specification to support up to 16 GB RAM when using 4 GB DIMMs based on 2 Gbit memory technology.

SPD for Samsung 4 GB DDR2 UDIMM (Intel DQ45CB board)

Obviously at that time DDR3 RAM was already available. In fact the same Intel Q45 chipset supports both DDR2 and DDR3 (though any given board would naturally only support one or the other type). This led to some curious situations; the above mentioned Intel DQ45CB board eventually supported up to 16 GB DDR2 memory, but the “better” DP45SG board from the same generation used DDR3 memory and never (at least officially) went beyond 8 GB maximum memory support.

It is worth noting that even though it was not officially listed as supported at the time, a DQ45CB board with BIOS version 0059 dated 08/25/2008 works just fine with the 4 GB modules. There is nothing in the DQ45CB BIOS revision history mentioning that support for 4 GB DIMMs was added to the firmware at some point after the initial release.

2x4GB UDIMMs in an Intel DQ45CB board

For good measure, I tried the 4 GB DIMMs in an older Intel D975XBX2 board. To my surprise, the board actually managed to POST, but the BIOS was very confused about the amount of installed memory and memtest86 crashed and burned almost instantly. Not that it was expected to work.

As is often the case with the largest memory modules of any given generation, there are several separate problems. The memory controller needs to support the given memory technology and DIMM architecture. Without that, the DIMMs can’t work at all.

On the Intel side, I believe that only the 4 Series chipsets (P45, Q45, P43 etc. ) supported 4 GB DDR2 modules (2 Gbit technology). That was also Intel’s last generation with DDR2 support and only came out a few months before the next-generation X58 chipset was released. In fact the 4 Series chipsets also supported DDR3, not just DDR2. Intel’s 3 Series and all older DDR2 chipsets did not support 2 Gbit DDR2 chips (although even the 3 Series chipset supported DDR3 already).

A separate problem becomes relevant when one tries to fully populate the memory. It might happen that, say, the chipset supports 4 GB modules but only supports up to 8 GB physical memory, and still can’t use 16 GB with four memory slots populated. I don’t believe this was the case with the Intel desktop chipsets and DDR2 4 GB modules; the 4 Series chips could support 16 GB physical memory, and the older ones with 8 GB maximum physical memory support didn’t work with 2 Gbit memory technology anyway.

Finally even when the chipset supports the memory technology and can address fully populated memory, the firmware needs to properly support it. Sometimes the hardware is capable but firmware gets in the way. That happened at several points with various memory generations and boards.

In summary, the reason for the rarity of 4 GB DDR2 modules is that by the time the chipsets with 4 GB DDR2 DIMM support were released, DDR2 was almost obsolete. The situation was different in the laptop market and that is why 4 GB DDR2 SO-DIMMs are not quite as exotic.

Things were somewhat different in the AMD camp. Since the memory controller was on the CPU, the board didn’t fully determine what memory was supported. Technologically there was another major difference between AMD and Intel: In the DDR2 times, Intel’s server hardware almost exclusively (the 5100 San Clemente chipset being the exception) used FB-DIMMs (fully buffered DIMMs), modules that looked similar enough but were significantly different from desktop memory. AMD’s Opterons on the other hand always used registered DDR2 which was not vastly different from typical desktop RAM.

High Density vs. Low Density, Ugh

For a long time now, there’s been debate about “high density” vs. “low density” DDR2 RAM and what is or isn’t supported by Intel vs. AMD. As it often is with Internet debates, the signal to noise ratio is extremely low.

The word on the street was that AMD CPUs, including desktop CPUs, supported “high density” DDR2 modules and Intel did not. The truth is that AMD desktop CPUs can work with non-standard 4 GB (and 2 GB) memory modules that do not work in Intel systems. Some of that has been previously discussed on this site.

As a case in point, let’s do a comparison. These are my 4 GB modules, Samsung M378T5263AZ3-CF7:

Genuine Samsung 4 GB DDR2 UDIMMs

Here’s a product photo (from an eBay auction) of a module with the exact same Samsung M378T5263AZ3-CF7 designation but obviously a very different layout; in fact while mine are labeled as 2Rx8 (dual rank, x8 chips), the other set is labeled 2Rx4:

Fake “Samsung” 4 GB DDR2 modules

According to Samsung, a module with M378T5263AZ3-CF7 designation has sixteen x8 chips (each chip with 256 MB or 2 Gbit capacity), from which one can conclude that mine are actual Samsung DIMMs and the others are one of the many “AMD only” fakes.

In fact there is another indication that the module is fake. That “4GB 2Rx4 PC2-6400U-666-12-E3” designation is actually a standard JEDEC product label. The last “E3” bit refers to a reference design using third revision raw card ‘E’ as given in the JEDEC standard. And, of course, raw card ‘E’ uses a 2Rx8 architecture with 16 chips total, not 2Rx4 with 32 chips total.

But back to density. No one knows what “high density” memory really means, because the term is by definition relative (and has been used with pre-DDR SDRAM, for example). Maybe “high density” refers to DDR2 memory with 2 Gbit chips, although sometimes it does not. As we’ve seen above, there are some Intel boards that actually do support such memory, even though they’re uncommon.

There appears to be some agreement that “high density” refers to the capacity of individual memory chips, not the number of chips on a DIMM. But then we have guides like this one where we’re told that 1 GBit chips are high density, but 1 Gbit chips are also low density (see explanation below on what the real problem is). To be fair, others have made the same claim.

There are also nuggets like this: “The easiest way to tell if your DIMM is high density is if there’s no name or manufacturer on the DIMM itself”. So now we know why unscrupulous sellers bother slapping obviously fake Samsung labels on sketchy DIMMs: That makes them low-density and therefore good!

Then we have Crucial, an actual memory manufacturer, telling us pretty clearly that “high density” means higher capacity chips, not that one 1 Gbit chip can be “low density” and another 1 Gbit chips “high density”.

But it’s even worse than that. That fake 4 GB Samsung module above obviously has 1 Gbit chips, that’s why it needs so many to get to 4 GB capacity. And that module does not work in an Intel board, whereas the real Samsung DIMM with higher density chips does work. So it’s not that “low density memory works in Intel boards and high density doesn’t”; when it comes to 4 GB DIMMs, only RAM based on high-density chips works in Intel boards!

The bottom line is that the terms “high density” and “low density” in the context of DDR2 RAM have been abused to death, are effectively meaningless, and should be avoided.

What Makes UDIMMs AMD Only?

OK, so if it’s not “density”, there must be something else that makes those “AMD only” DIMMs incompatible with Intel hardware. The answer is in the actual DDR2 UDIMM standard. Remember that “2Rx4” designation on the fake Samsung modules? That’s probably the only part of the label that isn’t fake.

According to the JEDEC PC2-5300/PC2-6400 DDR2 SDRAM Unbuffered DIMM Design Specification (Revision 3.2, 2012) there simply are no UDIMMs based on x4 architecture! Only x8 and x16 based UDIMMs are specified. Registered DDR2 for servers is different and can use x16, x8, and x4 chips (in fact x4 DDR2 server DIMMs are probably the most common). An older version of the DDR2 UDIMM specification can be found here; the 2012 update version can be obtained from the JEDEC website but it’s not very different.

Since Intel used completely different memory technology (FB-DIMMs) in their DDR2 server hardware, their server and desktop/mobile memory controllers were very different and the latter never supported x4 DDR2 memory chips. It’s not clear which was the chicken and which was the egg, but it is apparent that DDR2 UDIMMs never defined x4 modules because Intel never supported them, and Intel never supported x4 UDIMMs because they were never defined by the JEDEC standard. Certainly Intel’s 3 Series and 4 Series datasheets clearly say that they support x8 and x16 memory, while x4 is not mentioned.

Bottom line, DDR2 unbuffered DIMMs with x4 chips are non-standard, fake, and although they might work in AMD systems just fine, they will definitely not work with Intel chipsets.

Conclusion

So are the real 4 GB DDR2 DIMMs any good? Yes, if you have the hardware that can use them, which in the Intel world means a 4 Series chipset. I can imagine that they could be really useful for example in an Intel DQ45EK board which only has two memory slots. And in a DQ45CB board, or in one of the handful of non-Intel brand boards that reportedly support 4 GB DDR2 UDIMMs, it’s a rare opportunity to combine an Intel chipset based desktop Core 2 platform with 16 GB RAM.

DDR2 and DDR3 RAM became more expensive in November, while modern DDR4 remained stable

About ranks and virtualization in RAM Let’s take a closer look at the reliability of data storage in memory and those technologies that, countless times a day, save administrators from the sorrows of BSOD .

Today, there are mainly modules with DDR SDRAM memory on the market: DDR2, DDR3, DDR4. Different generations differ from each other in a number of characteristics — in general, each next generation is «faster, higher, stronger», and for the curious, here is a sign:

To select the right memory, the modules themselves are of more interest:

• RDIMM — registered (buffered) memory. Convenient for installing a large amount of RAM compared to unbuffered modules. Of the minuses — lower performance;

• UDIMM (unregistered DRAM) — unregistered or unbuffered memory — is random access memory that does not contain any buffers or registers;

• LRDIMM — These modules provide faster speeds with more capacity than dual-rank or quad-rank RDIMMs by using additional memory buffer chips;

• HDIMM (HyperCloud DIMM, HCDIMM) — modules with virtual ranks that have a higher density and provide higher speed. For example, 4 physical ranks in such modules can be presented to the controller as 2 virtual ones;

• FBDIMM is a fully buffered DIMM with high reliability, speed and density.

An attempt to use these types at the same time can cause a variety of unfortunate consequences, up to damage to the motherboard or the memory itself. But it is possible to use the same type of modules with different characteristics, since they are backward compatible in terms of clock frequency. True, the final frequency of the memory subsystem will be limited by the capabilities of the slowest module or memory controller.

For all types of SDRAM memory there is a common set of basic characteristics that affect the volume and performance:

Of course, there are actually more differences, but to build a properly working system, you can limit yourself to these.

It is clear that the higher the frequency, the higher the overall memory performance. But the memory will still not work faster than the controller on the motherboard allows it. In addition, all modern modules can work in multi-channel mode, which increases the overall performance up to four times.

Operating modes can be roughly divided into four groups:

• Single Mode — single-channel or asymmetric. Turns on when only one memory module is installed in the system or all modules are different from each other. In fact, it means no multi-channel access;

• Dual Mode — dual channel or symmetrical. Memory slots are grouped into channels, each with the same amount of memory installed. This allows you to increase the speed of work by 5-10% in games, and up to 70% in heavy graphics applications. Memory modules must be installed in pairs on different channels. Motherboard manufacturers usually highlight paired slots in the same color;

• Triple Mode — Triple mode. Modules are installed in groups of three — on each of the three channels. The subsequent modes work similarly: four-channel (quad-channel), eight-channel (8-channel memory), etc.

• Flex Mode — allows you to increase the performance of RAM when installing two modules of different sizes, but with the same frequency.

For maximum performance, it is better to set identical modules with the highest possible frequency for the system. In this case, use the installation in pairs or groups — depending on the available multi-channel operation.

Rank (rank) — a memory area of ​​several memory chips in 64 bits (72 bits in the presence of ECC, which will be discussed later). Depending on the design, a module may contain one, two or four ranks.

You can find out this parameter from the marking on the memory module. For example, at Kingston, the number of ranks is easy to calculate by one of the three letters in the middle of the marking: S (Single — single-rank), D (Dual — two-rank), Q (Quad — four-rank).

An example of a full decoding of markings on Kingston modules:

Server motherboards are limited by the total number of memory ranks they can work with. For example, if a maximum of eight ranks can be installed with four dual-rank modules already installed, then memory cannot be added to the free slots.

Before purchasing modules, it makes sense to check what types of memory the server processor supports. For example, the Xeon E5/E5 v2 supports single, dual, and quad-rank registered DIMMs (RDIMMs), LRDIMMs, and unbuffered ECC DIMMs (ECC UDIMMs) DDR3. And the Xeon E5 v3 processors support single- and dual-rank registered DIMMs, as well as DDR4 LRDIMMs.

Timings or memory latency (CAS Latency, CL) — the amount of delay in cycles from the receipt of a command to its execution. The timing numbers indicate the parameters of the following operations:

• CL (CAS Latency) – the time that elapses between the processor requesting some data from the memory and the moment the memory issues this data;

• tRCD (delay from RAS to CAS) – the time that must elapse from the moment the matrix row (RAS) is accessed until the matrix column (CAS) with the required data is accessed;

• tRP (RAS Precharge) — the interval from closing access to one row of the matrix, and before starting access to another;

• tRAS — pause to return the memory to the state of waiting for the next request;

• CMD (Command Rate) – time from activation of the memory chip to accessing it with the first command.

Of course, the lower the timings, the better for speed. But you will have to pay for low latency with a clock frequency: the lower the timings, the lower the clock frequency allowed for memory. Therefore, the correct choice would be the «golden mean».

There are also special more expensive modules marked «Low Latency», which can operate at a higher frequency at low timings. When expanding the memory, it is desirable to select modules with timings similar to those already installed.

Errors when storing data in RAM are inevitable. They are classified as hardware failures and intermittent errors (crashes). Parity memory is able to detect an error, but is not able to correct it.

Irregular error correction uses ECC memory, which contains an additional chip to detect and correct errors in individual bits.

The error correction method works as follows:

1. When writing 64 bits of data to a memory cell, a checksum of 8 bits is calculated.

2. When the processor reads data, the checksum of the received data is calculated and compared with the original value. If the sums do not match, it is an error.

3. If the error is one-bit, then the wrong bit is corrected automatically. If it is two-bit, the corresponding message for the operating system is transmitted.

The Advanced ECC technology is capable of correcting multi-bit errors in a single chip and can recover data even if the entire DRAM fails.

Error correction must be separately enabled in the BIOS

Most server memory modules are registered (buffered) — they contain data transfer control registers.

Registers also allow you to set large amounts of memory, but they introduce additional delays in operation. The fact is that each read and write is buffered in the register for one cycle before they get from the memory bus to the DRAM chip, so the registered memory is one cycle slower than the non-registered one.

For reasons of reliability, it is better for the server to use registered memory.

For the correct and fast operation of several processors, each of them needs to allocate its own memory bank for «direct» access. It is better to read about the organization of these banks in a particular server in the documentation, but the general rule is this: we distribute memory between banks equally and put modules of the same type in each.

If you had to install modules in the server with a lower frequency than required by the motherboard, you need to enable additional wait cycles in the BIOS when the processor is working with memory.

To automatically take into account all the rules and recommendations for installing modules, you can use special utilities from the vendor. For example, HP has an Online DDR4 (DDR3) Memory Configuration Tool.

Instead of a spatial conclusion, I will give general recommendations for choosing a memory:

• For HP multiprocessor servers, only registered error correction memory (ECC RDIMM) is recommended, and unbuffered ECC memory (UDIMM) for single processor servers.

3DNews Technologies and IT market. News financial news and analytics DRAM RAM went up in price in November… The most interesting in the reviews 03.12.2020 [13:58], Gennady Detinich TrendForce analysts noted an interesting situation in the market of DRAM memory chips. Between October and November, inclusive, DDR4 memory did not change in price, while less dense DDR3 and DDR2 chips became more expensive. The least dense DDR3 1 Gb and DDR2 512 Mb chips went up the most, and there is a logical explanation for this. According to experts, the SARS-CoV-2 coronavirus pandemic and the subsequent transition to self-isolation and remote work have spurred the demand for televisions and other electronics, and now even kettles fall into this category. All this has created an increased demand for memory for digital devices. Naturally, this is, first of all, low-density memory. The second reason for the increase in demand for DDR3 and DDR2 chips was the development of the 5G ecosystem and the growing need for modems, routers, switches and other active network equipment, which also actively consumes RAM, we emphasize, not the highest density. Finally, both South Korean DRAM manufacturers — Samsung and SK Hynix — are gradually withdrawing from the production of DDR3 and DDR2 memory chips, and some have completely stopped producing. Now companies such as Taiwanese Winbond, ESMT and Etron are taking the rap for them, which also does not contribute to lower prices. Finally, low-density memory is usually bought either in relatively small volumes, or it is done by small manufacturers. Thus, they do not have the opportunity to push through interesting prices and long-term contracts, and the market for short transactions, moreover, is subject to panic. All this also contributed to the monthly increase in the average selling prices of DDR3 and DDR2 chips. Image source: TrendForce TrendForce believes that this situation in the DRAM chip market will last until the first quarter of 2021, when server manufacturers can revive and start purchasing large quantities of DDR4. Up to this point, the situation with prices will be close to that observed in November. The dynamics of prices from October to November can be found in the table compiled by TrendForce specialists. Source: If you notice an error, select it with the mouse and press CTRL+ENTER. Related materials Permanent URL: 5 Headings: Hardware news, RAM modules, memory cards, flash drives, card readers, financial news and analytics, Tags: trendforce, dram, analytics, chip manufacturing ← В past To the future →