Question DRAM cache SSDs

[Pupq1]

In what scenario is an SSD that has DRAM cache useful? And how do I know that an SSD has DRAM cache?

 

[fzabkar]

@JohnnyLucky, where is your database?

 

[JohnnyLucky]

fzabkar - Up until 2015 the link to the ssd database was posted in one of the stickies located at the very top of this forum section. It was an arrangement I had with management at Tom's Hardware. I was also allowed to post the link to the ssd database in forum comments. The arrangement worked quite well for over 6 years. Then Purch acquired Tom's Hardware. Purch corporate policy does not allow forum members to post links to "personal" web sites. As a result I cannot post the url. You will have to use a search engine to find the "Johnny Lucky ssd database" by yourself.

USAFRet: ^5

 

[13thmonkey]

You mean this one? http://www.johnnylucky.org/data-storage/ssd-database.html

 

[fzabkar]

Thank you. That's an excellent body of work.

One observation. Some SSDs do not specify the controller, and others do not specify the DRAM. Obviously (?) there are no controller-less SSDs, but there are DRAM-less ones. How does one differentiate between genuine DRAM-less SSDs and those for which the DRAM exists but is unidentified?

Also, some controllers are rebadged OEM versions. Would you consider cross-referencing them, or adding a database specifically for controllers? I could help with that, if you wish.

For example, Phison PS5012-E12 8-channel controller (aka ‘E12’ controller) = Seagate STXYP016C031.

Seagate FireCuda 510 = Silicon Power P34A80

https://www.hardwarecooking.fr/test-ssd-seagate-firecuda-510/
https://www.realhardwarereviews.com/silicon-power-p34a80/3/

 

[JohnnyLucky]

fzabkar asked: How does one differentiate between genuine DRAM-less SSDs and those for which the DRAM exists but is unidentified?

It is not unusual for some information about ssd's to be missing. Typically the information is missing if ssd's are more than 2 years old. The requests for DRAM information are new. I did not start receiving them until the beginning of this year. I did not start receiving requests for endurance ratings related to warranties until last year.

fzabkar also asked about rebadged OEM products. Many years ago we experienced the first rebadged Micron/Crucial ssd's. I distinctly remember a technical review where the enclosure was removed from a well known standard 2.5 inch SATA 2 drive. Inside the enclosure was a Micron/ Crucial ssd with Crucial labels and Crucial markings. In another incident Kingston used to have its own logo and Kinston model numbers silk screened onto OEM parts. It was extremely difficult to identify the OEM.

However, there is another problem. Although the controller, flash memory, DRAM, and other components may be identical for several brands, there is a distinct possibility that features, firmware, and embedded code may not be the same. This was mentioned jn one of the reviews you linked to.

Right now the few PCIe 4.0 x 4 ssd's use the same Phison controller, the same Toshiba 3D flash memory, and probably the same SK Hynix DRAM. Phison was simply first to market a PCIe 4.0 controller. We do not yet know if all of them have the same features enabled or disabled in firmware or embedded code. A company usually negotiates with an OEM. Eventually an agreement is reached which specifies the configuration, features that are enabled, and price.

On top of that, there are regional differences for the same model number. An ADATA model available in the Russian Federation may not have the exact same features as the same ADATA model sold in North America.

 

[fzabkar]

I'm suggesting that, in the case of known DRAM-less SSDs, you identify them as "DRAM-less" in the database rather than leaving this field blank. This distinguishes them from those cases where the DRAM status is unknown.

 

[JohnnyLucky]

fzabkar - I did identify ssd's that did not have DRAM modules. However, instead of using "DRAM-less" I simply used the word "None". There are very few of them. They simply are not very popular.

As I previously stated a few Silicon Motion "XT" controllers and a few Realtek controllers do not use DRAM. There is also a variation of a Phison S11 series controller that can be configured with or without DRAM. It is an older model. The ones listed in the database are configured with DRAM.

All of the blanks in the DRAM column simply mean the information is not yet available to me. The blanks do not mean the ssd's are DRAM-less. If and when the information becomes available I will update the database.

 

[JohnnyLucky]

MAJOR UPDATE - I knew dram-less ssd's were not very popular but I could not remember why. I decided to do some research.

1. Years ago when the M.2 international standards were being developed, one of the design concepts was a M.2, 2230, single sided, dram-less, ssd. It would be short enough and thin enough to fit inside small mobile pc's and other devices. Those small dram-less ssd's were never designed for use in desktop pc's.

2. I also looked at some of the advertising at company web sites. The companies are still advertising the small dram-less ssd's as being "perfect for netbooks and ultrabooks". I was surprised to see the terms netbooks and ultrabooks still being used. Most of the ads now say the ssd's are for small mobile pc's and other devices.

3. The tradeoff for the original dram-less ssd's was lower performance.

4. There has been a transformation over the last two years. We started seeing 2280 M.2 ssd's that appear to be dram-less. However, that does not mean the ssd's do not have some sort of memory used as a buffer or cache. So far, I have found dram-less ssd's with the following memory variations:

a. Host Memory Buffer (HMB)
b. SLC caching
c. SDRam
d. Dram cache buffer embedded in controller

The ssd database has been updated to reflect type of buffer or cache the newer dram-less ssd's use - providing the information is available.