Efficient HMB versus premium DRAM
Lexar NM790 vs WD_BLACK SN850X
Compare the efficient HMB-based Lexar NM790 with the DRAM-equipped WD_BLACK SN850X. Live pricing, capacity, workload and host fit determine which Gen 4 drive offers better value.
Same-capacity offers · Cooling variants separated · Price-aware verdict · Updated now
Live same-capacity market
Current price and value comparison
Recorded by Cloudzat
Observed family price-per-TB history
The chart appears after at least two genuine daily observations. It does not backfill synthetic historical prices.
Price-aware recommendation
Which SSD should you buy for this system?
Match the capacity, cooling, host and workload. The result uses current eligible prices instead of declaring a permanent winner.
Official family specifications
Specification differences that affect the decision
| Specification | Lexar NM790 | WD_BLACK SN850X |
|---|---|---|
| Interface | PCIe 4.0 x4 | PCIe 4.0 x4 |
| Official capacities | 512GB, 1TB, 2TB, 4TB, 8TB | 1TB, 2TB, 4TB, 8TB |
| Peak sequential read | 7,400MB/s | 7,300MB/s |
| Peak sequential write | 6,500MB/s | 6,600MB/s |
| NAND | TLC | 3D TLC |
| Cache architecture | HMB | DRAM |
| Cooling variants | Bare through 8TB; heatsink through 4TB | Bare and factory-heatsink |
| Warranty class | 5 years or TBW limit | 5-year limited |
Family maximums do not apply equally to every capacity. The live offer table and decision tool use the normalized capacity-specific values where available.
This is a value-versus-premium architecture comparison
The NM790 and SN850X both deliver high PCIe 4.0 throughput, but they reach the market through different designs. Lexar uses Host Memory Buffer rather than dedicated onboard DRAM, helping the NM790 target efficiency and aggressive pricing. The SN850X uses a premium gaming design with dedicated cache resources and a broader software feature set.
Neither architecture automatically wins every workload. Cloudzat combines live same-capacity pricing with the selected use case. General storage and gaming may reward the lower NM790 price, while sustained or mixed workloads can give the SN850X’s DRAM-equipped design more value.
Compare matching capacities, including the 8TB tier
Both families extend to 8TB, making them important for users who need maximum capacity in one M.2 slot. The exact 8TB performance specifications differ from smaller models, so the page does not copy the 1TB or 2TB peak figures across the range.
At 1TB, 2TB and 4TB, discounts can switch the price winner frequently. At 8TB, density and availability can matter more than a small price-per-terabyte difference. The tool uses the selected capacity and reports when one family lacks enough verified offers for a reliable comparison.
HMB does not mean slow
The NM790 uses system memory through Host Memory Buffer for mapping support instead of carrying dedicated DRAM on the SSD. That design can still deliver excellent read performance and strong gaming results. It should not be confused with the weakest entry-level DRAM-less drives, because controller, NAND and firmware quality also matter.
HMB relies on host support and can behave differently under sustained or highly mixed workloads. The SN850X’s dedicated DRAM architecture may provide more consistent behavior in certain professional tasks. The workload selector gives that distinction more weight for workstation use than for a game library.
Peak performance and practical differences
The NM790 reaches up to approximately 7,400MB/s on its mainstream capacities, while the SN850X reaches up to approximately 7,300MB/s on 1TB through 4TB. The 8TB models have their own lower maximum ratings. These numbers place both products in the high-end Gen 4 class.
A small peak-read difference does not establish a universal winner. Game loading, file copies, cache exhaustion and thermal state can produce different rankings. Current price, capacity and sustained workload behavior should be evaluated together.
Laptop efficiency and physical construction
The NM790 is often attractive for laptops because of its efficient design and availability in bare configurations. High-capacity modules can become double-sided, so physical clearance must still be checked. The SN850X also has bare models, but its gaming positioning and heatsink options can be better suited to desktop or console installations.
The laptop mode excludes integrated-heatsink variants and reduces the value of features the host cannot use. It also emphasizes capacity and efficiency over peak benchmark differences. Buyers should verify the exact module thickness for 4TB and 8TB models.
PlayStation 5 and heatsink planning
Both families can be used in console-oriented configurations when the exact drive meets requirements and a suitable heatsink is present. Factory-heatsink availability differs by capacity, especially in the NM790 family, so the checkout variation must be reviewed carefully.
A bare drive plus a compatible third-party cooler can be cost-effective, but it should be compared as a complete installation. Cloudzat’s integrated-heatsink filter avoids presenting the bare-drive sticker price as the ready-to-use console cost.
Endurance and warranty value
Lexar publishes capacity-specific endurance figures for the NM790, and Western Digital does the same for the SN850X. Larger capacities receive higher total write allowances. The page calculates endurance per dollar using the selected live offer and never applies the 8TB figure to a smaller product.
Most gaming systems will not approach either warranty write limit. For a workstation cache, database or production scratch drive, sustained behavior and endurance deserve more weight. The result can therefore favor the SN850X even when the NM790 has the lower headline price.
When the NM790 is the stronger purchase
Choose the NM790 when it is materially cheaper, when laptop efficiency is important, or when a high-capacity game and media library is the primary use. Its HMB architecture can deliver excellent practical performance without the premium associated with dedicated DRAM.
The lowest price should still be verified against the exact SKU, condition and heatsink status. An accessory or incomplete listing must not be allowed to determine the value verdict. The normalized catalogue’s risk controls remove those products from the public sample.
When the SN850X is worth the premium
Choose the SN850X when the price gap is modest, dedicated DRAM and WD_BLACK software are valued, or the workload involves heavier mixed writes and sustained activity. Its factory-heatsink options and mature gaming ecosystem can also simplify a desktop or PS5 installation.
A large premium is harder to justify for ordinary gaming. The live score changes with current offers, so the page can recommend the NM790 during a strong Lexar promotion and switch back when the SN850X receives the better discount.
Understand how the host supplies memory to HMB
Host Memory Buffer allows the NM790 to use a small portion of system memory for mapping information. The operating system and NVMe driver must support that feature, and the amount involved is modest compared with normal system RAM. It does not turn the SSD into a substitute for a drive with dedicated DRAM in every access pattern.
Modern Windows and Linux systems generally provide the necessary NVMe support, but unusual appliances, older firmware and some enclosures deserve extra verification. The SN850X keeps its cache resources on the drive and is less dependent on host memory behavior. That architectural difference is most relevant in sustained mixed workloads, not as a blanket judgment about quality.
Methodology and official references
Cloudzat compares only normalized offers with matching capacity evidence. Cooling variants and condition are separated, the lowest eligible offer for each canonical product is retained, and the live verdict limits effective performance to the selected host interface. Historical values come only from recorded Cloudzat snapshots.
Frequently asked questions
Is the Lexar NM790 DRAM-less?
It uses Host Memory Buffer instead of dedicated onboard DRAM. That does not make it inherently slow, but workload behavior differs from a DRAM-equipped design.
Which is faster, NM790 or SN850X?
Their peak Gen 4 read ratings are close. Real results vary by capacity, cache state, thermals and workload, so there is no permanent universal winner.
Which is better for a laptop?
The NM790 can be attractive for efficient bare-drive laptop installations. Confirm module sidedness and clearance, especially at 4TB and 8TB.
Should I choose the NM790 or SN850X for a PS5 installation?
Either can work with a suitable heatsink and compatible exact SKU. The SN850X has broad factory-heatsink availability, while some NM790 capacities may require a separate cooler.
Do both drives offer 8TB?
Yes, current product ranges include 8TB options, but their performance and physical construction differ from smaller capacities.
How much cheaper should the NM790 be?
For gaming and general use, a discount near 10 to 15 percent often makes the NM790 the stronger value. Workstation users may accept a smaller gap for the SN850X’s DRAM and software features.