BLOG
For games, the operating system and ordinary office work, a good 2 TB PCIe 4.0 NVMe SSD is usually the sensible choice when it costs less than a comparable Gen5 drive. PCIe 5.0 makes more sense when your motherboard provides a full Gen5 M.2 slot, the cooling fits your case and long transfers between equally fast devices are a regular part of your work. The sequential number on the box is not the time it takes a game to open.
To make the comparison concrete, this article uses the 2 TB WD_BLACK SN850X (PCIe 4.0, no-heatsink model WDS200T2X0E) and the 2 TB Crucial T705 (PCIe 5.0, CT2000T705SSD3 without heatsink or SSD5 with heatsink). They are two identified drives, not representatives of every Gen4 and Gen5 model. Their US availability, price and warranty should be checked at the time of purchase.
The specifications that matter
| Specification | WD_BLACK SN850X 2 TB | Crucial T705 2 TB |
|---|---|---|
| Interface and format | PCIe 4.0 ×4, NVMe, M.2 2280 | PCIe 5.0 ×4, NVMe, M.2 2280 |
| Advertised sequential read | Up to 7,300 MB/s | Up to 14,500 MB/s |
| Advertised sequential write | Up to 6,600 MB/s | Up to 12,700 MB/s |
| Rated endurance | 1,200 TBW | 1,200 TBW |
| Thermal options | Check the specific no-heatsink or heatsink SKU | SSD3 without heatsink; SSD5 with heatsink |
These are manufacturer maxima and rated endurance figures for the named capacities, not promises of sustained speed for every file, laptop or M.2 slot. Compare identical capacities and correct SKUs. A “2 TB SN850X” listing with a heatsink has a different physical height from the no-heatsink version, which matters in a laptop or a motherboard with its own cover.
Why twice the MB/s does not mean half the loading time
Sequential tests move large blocks under controlled conditions. Loading a game or application involves many file sizes, decompression, CPU work, memory and initialization. Therefore, 14,500 versus 7,300 MB/s cannot honestly be converted into a claim that a game loads twice as fast. Replacing only the SSD generation also does not inherently raise frame rate when a game already runs normally.
Microsoft’s DirectStorage documentation describes an API intended to help games exploit fast storage and many small reads with lower CPU overhead. It does not make every game load instantly, and a user cannot assume that every title implements it or that it requires PCIe 5.0. The game, software path and the rest of the PC determine the observed result.
If you are deciding between a 1 TB Gen5 drive and a 2 TB Gen4 drive, capacity may be the larger practical difference. A game library that nearly fills 1 TB creates more friction through uninstalling and moving titles than a benchmark advantage can solve. Confirm the current drive is actually the bottleneck before purchasing speed you cannot use.
Where PCIe 5.0 can save time
Consider a creator copying hundreds of gigabytes of raw media between two fast internal NVMe drives. The additional Gen5 bandwidth may reduce that transfer if the source, destination, bus, cache and thermal behavior all keep pace. Copying from a hard drive, SATA SSD, USB stick, memory card or slow network does not exploit the T705’s peak write capability. The slowest component sets the transfer rate.
Even “I edit 8K” is insufficient evidence. The time-consuming step might be reading source media, rendering through a CPU/GPU-bound codec, generating proxies or exporting a final file to a slower device. Measure the operations separately. If the long wait is an internal copy between two fast NVMe drives, Gen5 deserves consideration. If the wait is codec processing, changing only the destination SSD is unlikely to eliminate it.
Measure the bottleneck before spending
Gaming example: a player with a 1.6 TB library may need room more than peak bandwidth. Compare the cost of 2 TB Gen4 with 1 TB Gen5 and measure current load times. Check CPU, RAM and game implementation before blaming storage. A drive that has adequate speed but too little capacity can make everyday management harder.
Editing example: a small production team receives 400 GB of media per project. Time the copy into the working drive and the final export separately. If the copy is between two quick NVMe drives and dominates the workflow, a T705-class device may be justified. If the source is a card reader or NAS, or export is processor-bound, the headline Gen5 speed does not address the principal delay. These are illustrative scenarios, not benchmarks we ran.
Compatibility: the slot sets the ceiling
Before buying a Gen5 drive, open the desktop or laptop manual and identify the exact M.2 slot that supports PCIe 5.0 ×4. Some motherboards provide Gen5 on only one slot; others share lanes with another slot or a graphics connector under specific configurations. Crucial’s T705 installation guide explicitly advises using a slot that supports the drive’s generation for full performance.
The T705 is backward compatible with PCIe 4.0 and 3.0 according to the manufacturer’s flyer, but it cannot exceed the slot’s link speed. If your system is Gen4-only, paying extra for a Gen5 peak provides no Gen5 interface benefit there. Check M.2 2280 length and the height allowed under a laptop bottom cover or desktop GPU. A preinstalled heatsink that works in an open desktop can be physically impossible in a notebook.
When upgrading from SATA or a hard drive, a good NVMe drive may already produce the biggest practical improvement. Gen4 versus Gen5 is a second decision after confirming the system accepts NVMe at all and has a suitable slot. For a PS5, use the console’s own SSD requirements and a physically compatible heatsink; do not infer console support from desktop Gen5 marketing.
Heat: a heatsink matters; a dedicated fan is not universal
The T705 needs a thermal plan to sustain high transfer rates. Crucial says its no-heatsink version should be installed with a motherboard or alternate heatsink for optimal performance. Its flyer identifies the taller factory-heatsink version. Under the manufacturer’s stated typical airflow and ambient conditions, the preinstalled heatsink can avoid a dedicated fan; that does not guarantee the same result in every sealed case or laptop.
The SN850X also benefits from appropriate cooling. Gen4 is not a synonym for “cold.” SSD temperature depends on the motherboard location, the presence of a heatsink, GPU exhaust, case airflow, workload and ambient conditions. Under long writes, a drive may reduce speed to protect itself. Read thermal data for the exact installed configuration, not a claim based on generation alone. Avoid stacking two heatsinks or removing factory labels contrary to the manufacturer’s instructions.
Pros and limits of each 2 TB model
WD_BLACK SN850X 2 TB
The SN850X data sheet documents high Gen4 sequential rates, 1,200 TBW endurance for 2 TB and a five-year limited warranty. It can use the full Gen4 link on a suitable board, making it a coherent gaming and general-work choice. Its limitation is that it cannot provide a Gen5 link’s peak bandwidth for long, otherwise unconstrained transfers. A compact, warm case still needs thermal consideration.
Crucial T705 2 TB
The T705 flyer lists almost double the advertised sequential read of the SN850X and the same 1,200 TBW rating at 2 TB. It offers a factory-heatsink option. The trade-offs are a need for a true Gen5 slot to realize the interface advantage, physical and thermal planning, and a workload that converts bandwidth into saved time. The T705’s larger number on a box does not prove an advantage in a specific game or render.
Compare the real cost
Record the final delivered price of both drives at the same capacity and warranty level, including shipping, taxes and whether a heatsink is included. Do not assume that the T705 always costs twice as much; US inventory and discounts change. If time savings are the argument for Gen5, estimate how often a relevant copy operation occurs and measure the current delay. If you never run that operation, the performance premium may have no practical payback.
Also consider failure recovery. Neither model replaces backups. Store important projects in another location or service and test restore, particularly when a drive is used as a production scratch disk. Rated TBW is an endurance specification, not a promise that a drive cannot fail before that point.
Frequently asked questions
Does PCIe 5.0 improve FPS?
Not by itself. Frame rate is primarily affected by the game, CPU, GPU and memory. Storage influences loading and data access, with game-specific behavior.
Will the T705 work in a PCIe 4.0 slot?
Crucial specifies backward compatibility, but speed is limited by the slot. Confirm the motherboard’s exact slot and firmware support before purchase.
Does the T705 need its own fan?
Not as a universal rule. The factory-heatsink version is specified for maximum workload under typical airflow and ambient conditions without a dedicated fan. The no-heatsink version needs suitable motherboard or alternate cooling, and hot cases require individual evaluation.
Verdict by workload
For gaming and everyday work, choose a properly cooled SN850X-class Gen4 drive when it is cheaper and your system has Gen4. For a workstation moving massive files between equally fast internal devices, compare the T705 after confirming a Gen5 slot, destination speed and cooling. For laptops, physical clearance may be the deciding constraint. On a Gen4-only motherboard, the T705 cannot deliver its Gen5 link advantage. Pay for capacity, reliability and fit before purchasing an impressive sequential number that your work cannot turn into useful time.
