Review Index:

Intel SSD 660p 1TB SSD Review - QLC Goes Mainstream

Subject: Storage
Manufacturer: Intel
Tagged: ssd, SMI, QLC, Intel, 660p, 512GB, 3d nand, 2TB, 1TB

Introduction, Specifications, and Packaging


Flash Memory Summit 2018 is on, and it's rapidly looking like the theme of the year is 'QLC'. QLC stands for Quad Level Cell, which is a bit of a misnomer since there are actually 16 voltage levels of a QLC cell - the 'quad' actually relating to the four bits of data that can be stored at any specific location.

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Doubling the number of voltage states allows you to store 33% more data in a given number of flash cells, but comes at a cost. The tighter voltage tolerances required and higher sensitivity to cell leakage mean that endurance ratings cannot be as high as TLC or MLC, and programming (writing) requires greater voltage precision, meaning slower writes. Reads may also see a slight penalty since it is more difficult to discriminate more finely grained voltage thresholds. SSD makers have been trying to overcome these hurdles for years, and it seems that Intel is now the first to crack the code, launching their first mainstream QLC SSD:

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Specifications are not earth shattering but respectable for a budget-minded NVMe SSD. 1.8GB/s sequentials and 250,000 IOPS fall well within NVMe territory. The write figures may be higher than expected given this article intro, but Intel has a few tricks up their sleeves here that help them pull this off:

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While not specifically called out in the specs, Intel has implemented a large dynamic write cache to help overcome slower QLC media write speeds. The idea here is that in the vast majority of typical usage scenarios, the user should never see QLC speeds and will only ever be writing to SLC. The dynamic cache is created by simply operating sections of the QLC media in SLC mode (1TB of QLC = 256GB of SLC). Intel could have gone higher here, but doing so would more negatively impact endurance since erasing blocks of cells wears the flash similarly regardless of the mode it is currently operating in.


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Simple packaging. Nothing to write home about.

Read on for our full review of the Intel SSD 660p 1TB QLC SSD!

Review Terms and Disclosure
All Information as of the Date of Publication
How product was obtained: The product is on loan from Intel for the purpose of this review.
What happens to product after review: The product remains the property of Intel but is on extended loan for future testing and product comparisons.
Company involvement: Intel had no control over the content of the review and was not consulted prior to publication.
PC Perspective Compensation: Neither PC Perspective nor any of its staff was paid or compensated in any way by Intel for this review.
Advertising Disclosure: Intel has not purchased advertising at PC Perspective during the past twelve months.
Affiliate links: This article contains affiliate links to online retailers. PC Perspective may receive compensation for purchases through those links.
Consulting Disclosure: Intel is a current client of Shrout Research for products or services related to this review.

Video News

August 7, 2018 | 12:29 PM - Posted by Mobile_Dom

holy shitballs this is pretty impressive.

I cant wait to see this with Samsung Controllers and NAND. Though, at 20c per gig, getting one of these on a sale will be an insane steal.

August 7, 2018 | 02:55 PM - Posted by Allyn Malventano

Totally with you on price. Intel has undercut the market a few times in the past and I’m happy to see them doing it again. I’d also like to see Samsung come down to this same price point.

February 12, 2019 | 07:44 AM - Posted by Fred (not verified)

Thought that too, when it came out. But now it's down to around 10c per gig, at least in Germany, which it should have launched at. Now I'm definitely considering getting one, but I might wait for a sale since I'm stingy.

August 7, 2018 | 12:30 PM - Posted by TropicMike (not verified)

You forgot an edit - Toshiba:

PC Perspective Compensation: Neither PC Perspective nor any of its staff was paid or compensated in any way by Toshiba for this review.

August 7, 2018 | 01:38 PM - Posted by protoCJ

Well, I'd be surprised if Toshiba paid for this review.

August 7, 2018 | 02:48 PM - Posted by Allyn Malventano

Fixed. Thanks for the catch guys!

August 11, 2018 | 12:47 PM - Posted by albert89 (not verified)

PC per has a long history of shilling for Intel and Nvidia at the cost of AMD. As far as I can tell they have no reason to change. Their motto is fake tech reviews and to hell what anyone thinks.

August 13, 2018 | 04:17 PM - Posted by Allyn Malventano

Yeah, such a long history of that ( is previously / Also funny how our results line up with other reviews. Must be some grand conspiracy theory against AMD. /sarcasm

August 14, 2018 | 07:13 AM - Posted by Kareha

This is why I wish Ryan would turn verified comments back on so asshats like the previous one don't post. I don't understand why it was turned off in the first place, it made the comment sections much more bearable and pleasant to read, now, not so much.

August 7, 2018 | 01:43 PM - Posted by Paul A. Mitchell (not verified)

Allyn, Going way back to a conversation we had many months ago (years?), given the low price per GB, is there any performance to be gained by joining these QLC devices in a RAID-0 array? The main reason why I ask is the "additive" effect of multiple SLC-mode caches that obtains with a RAID-0 array. I'm using this concept presently with 4 x Samsung 750 EVO SSDs in RAID-0 (each cache=256MB), and the "feel" is very snappy when C: is the primary NTFS partition on that RAID-0 array. How about a VROC test and/or trying these in the ASRock Ultra Quad M.2 AIC? Thanks, and keep up the good work!

August 7, 2018 | 02:53 PM - Posted by Allyn Malventano

Yeah RAID will help as it does with most SSDs. For SSDs with dynamic caches, that means more available cache for a given amount of data stored, and a better chance that the cache will be empty since the given incoming write load is spread across more devices.

August 8, 2018 | 12:21 PM - Posted by Paul A. Mitchell (not verified)

Many thanks for the confirmation. I don't have any better "measurement" tools to use, other than the subjective "feel" of doing routine interaction with Windows. But, here's something that fully supports your observation: the "feel" I am experiencing is snappier on a RAID-0 hosted by a RocketRAID 2720SGL in an aging PCIe 1.0 motherboard, as compared to the "feel" I am sensing on a RAID-0 hosted by the same controller in a newer PCIe 2.0 motherboard. The only significant difference is the presence of DRAM cache in all SSDs in the RAID-0 on the PCIe 1.0 motherboard, and the SSDs on the newer PCIe 2.0 motherboard have no DRAM caches. I would have expected a different result, because each PCIe lane in the newer chipset has twice the raw bandwidth of each PCIe lane in the older chipset. With 4 x SSDs in both RAID-0 arrays, the slower chipset tops out just under 1,000 MB/second, whereas the faster chipset tops out just under 2,000 MB/second.

August 8, 2018 | 12:31 PM - Posted by Paul A. Mitchell (not verified)

p.s. Samsung 860 Pro SSDs are reported to have 512MB LPDDR4 cache in both the 256GB and 512GB versions:

As such, a RAID-0 array with 4 such members has a cumulative DRAM cache of 512 x 4 = 2,048MB (~2GB LPDDR4).

August 9, 2018 | 11:10 PM - Posted by Allyn Malventano

DRAM caches on SSDs very rarely cache any user data - it’s for the FTL.

August 12, 2018 | 01:40 PM - Posted by Paul A. Mitchell (not verified)

Thanks, Allyn. FTL = Flash Transaction Layer

August 7, 2018 | 03:51 PM - Posted by Dark_wizzie

So the tests are done with practically a full drive, right? Written sequentially except for last 8GB which are written to randomly. In a normal drive even when My Computer says the drive is full there is still a little bit of space left over, so you put 18GB of space free. So is this test simulating what it's like to have a full or close to full drive from the user's perspective?

Anandtech's tests made a big deal about performance changing from empty versus full. Anandtech didn't figure out when that performance drops (if it's a cliff or a gradual decline), but it almost makes the reader feel like you might want to buy double the capacity you normally need just to be safe. It's probably not that bad, but it feels like that emotionally.

August 7, 2018 | 04:22 PM - Posted by Allyn Malventano

Performance gains due to drive being empty are typically leveled out once you hit 10-20% or so (lower if you’ve done a bunch of random activity like a Windows install, etc. My suite does a full pass of all measurements at three capacity points and then applies a weighted average to reach the final result. The average weighs half full and mostly full more heavily than mostly empty performance. The results you see in my reviews are inline with what you could expect with actual use of the drive.

August 7, 2018 | 05:07 PM - Posted by Power (not verified)

"Heavy sustained workloads may saturate the cache and result in low QLC write speeds."

Looks like up to a third of good HDD level, right? Scary.

August 9, 2018 | 11:11 PM - Posted by Allyn Malventano

A third sequentially. Random on HDD is still utter crap. Also, it’s extremely hard to hit this state in actual use. I was trying. 

August 7, 2018 | 07:32 PM - Posted by asdf1 (not verified)

hey Allyn, is there a way to include these few tests. one where exam QLC sequential write performance once SLC buffer fills up. another being similar to Anand's sequential fragmentation sequential performance testing for both read/write.

August 9, 2018 | 11:17 PM - Posted by Allyn Malventano

The sustained write performance appears in two tests - saturated vs. burst (where I show it at variable QD - something nobody else does), and on the cache test, where you can see occasional dips to SLC-> QLC folding speed. Aside from a few hiccups it did very well and was able to maintain SLC speed during the majority of a bunch of saturated writes in a row. If you need more than that out of your SSD and the possibility of a slow down is unacceptable, then QLC is not for you and you’ll need to step up to a faster part.

August 7, 2018 | 07:34 PM - Posted by asdf1 (not verified)

oh and FFS PLEASE PLEASE remove google recaptcha its a waste of time, it took me TEN minutes to solve and to make 1 post

August 8, 2018 | 09:13 AM - Posted by Anonymous2 (not verified)

And you wasted it on that?

August 8, 2018 | 09:34 PM - Posted by ReCrapThisGoogleYouSuck (not verified)

Google Recaptcha and street signs! All those damn street signs and no proper explanation of just what Google considers a street sign. If you get too good at solving the ReCrapAtYa the AI thinks you are an automated bot!

Google's ReCrapAtYa AI has gone over to the HAL9000 side and is evil to the power of 1 followed By 100 zeros! Just like Google's search AI that forces you to accept it's twisted judgment of just what it thinks you are looking for that's not actually what you where looking for. Google's search engine has become the greatest time thief in history of research.

Google's Recaptcha AI is the damn Bot and Google search now returns mostly useless spam results. Google is a threat to civilization!

August 9, 2018 | 11:13 PM - Posted by Allyn Malventano

Sorry. Without that we spend more time culling spam posts than we do writing articles. 

August 11, 2018 | 08:01 AM - Posted by EddieObscurant (not verified)

Nice review, Allyn the dram on the 660p is 256mb and not 1gb.
You can also confirm it with the other reviews of the 660p.

Why do you think intel choose that size instead of the classic 1mb dram for 1gb nand?

Do you think it hampered performance?

August 15, 2018 | 12:10 PM - Posted by Anonymoo (not verified)

Dumb question time:
is it possible to make the entire drive work in SLC mode? With the size of the drives these days I could sacrifice the space for the speed and reliability.

August 15, 2018 | 02:23 PM - Posted by Allyn Malventano

So long as you only partition/use 1/4 of the available capacity, the majority of the media should remain in SLC-only mode.

August 16, 2018 | 04:52 PM - Posted by Anonymoo (not verified)

I wonder if there is a way to force it at the firmware level. Might be a good selling feature. I am sure i am not the only overcautious nerd who would value a modern 'SLC' drive.

August 16, 2018 | 08:36 PM - Posted by pgj1 (not verified)

I didn't see any mention of which NVMe drivers were used during this review. Not sure if the Windows drivers are much different than Intel's own drivers.

August 18, 2018 | 12:32 PM - Posted by JokesOnYou77

@Allyn, you mentioned in the podcast that you weren't able to saturate the writes with a copy. Rather than doing a copy have you considered creating data in RAM and then writing that? For example, create a huge numpy float and write it as binary to disk. Or a simple C program that just writes random noise to disk in a while 1 loop. Maybe even just pipe /dev/urandom to a file in several different terminals at once.

August 27, 2018 | 09:14 AM - Posted by Nick (not verified)

Hello, Allyn!
Did you use IPEAK to create custom trace-based test suite?

September 6, 2018 | 04:49 PM - Posted by Allyn Malventano

IPEAK and similar developer tools were used to capture traces, but our suite's playback workloads are based on analysis of those results, not directly playing back the streams. We do this so that we can properly condition and evaluate SSDs of varying capacities, etc.

September 10, 2018 | 05:50 PM - Posted by Cerebralassassin

May I ask when these 660p NVMe ssds will be readily available in the market place? I see the 512GB model at but neither that sku or any other sku at OR OR anywhere... :( I would like to buy the 1TB model personally.

January 29, 2019 | 03:44 PM - Posted by cw (not verified)

Don't buy from the evil non-tax-paying Intel corporation. Crucial have a new 1Tb QLC nvme ssd, Write Endurance 200Tb, 1Gb dram cache, at (CA$192, US$145):

November 11, 2018 | 10:41 PM - Posted by CrazyTasty (not verified)

First of all, thanks for all of your ridiculously in-depth storage reviews. PC Perspective is my first, and usually only, stop when looking to purchase new storage.

Second, I believe there is a typo on the "Conclusion" page. You listed the 2TB endurance as "200TBW" instead of the "400TBW" Intel specs it as on ARK.

Happy Veterans Day from a fellow vet. Thank you for your service!

December 29, 2018 | 04:30 PM - Posted by ClearStale (not verified)

All three capacities have 256MB of DRAM, not 1GB. This was already pointed out by a previous reader.

Also, the 660p uses a static SLC cache that is 6GB, 12GB, or 24GB, along with a dynamic SLC pool.

It's possible this drive is using Host Memory Buffer or compressing the LBA map.

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