In the evolving landscape of professional computing, the traditional workstation is radically transforming. For years, the Mac Pro represented the pinnacle of expandability in Apple's ecosystem—a tower of power where professionals could add specialized PCIe cards for everything from video capture to audio processing. Yet Apple Silicon has rewritten the rules, delivering astonishing performance in smaller packages while leaving professional users with a critical question: what about expansion?


For the past several years, I've dedicated much of my content to the Mac Pro lineup—writing guides and producing videos. However, after my 2019 Mac Pro, I'm likely not buying another Mac Pro. The single Mac Pro entry in the Apple Silicon era has been woefully underwhelming, offering PCIe slots for a $3,000 premium that can only be used for expansion cards. YouTuber Luke Miani aptly described it as "Expandable, not upgradeable.

But what if there was a way to bring true PCIe expansion to any Mac? The advent of Thunderbolt 5 now enables 4x PCIe 4.0 speeds through external connections. For professionals in video production, audio engineering, and scientific computing who rely on specialized PCIe hardware, this opens intriguing possibilities: Could a Mac Studio or even a Mac mini paired with the right expansion chassis replace a Mac Pro?

This is where the Sonnet Echo II DV enters the picture—a dual-slot Thunderbolt PCIe expansion chassis with a unique twist: each PCIe slot gets its own dedicated Thunderbolt bus. This approach promises to eliminate the bandwidth bottlenecks that have historically plagued external expansion solutions. This design could be a game-changer for professionals who need to run bandwidth-intensive cards like BlackMagic DeckLink 8K Pro or AJA KONA 5 capture cards alongside high-speed storage.

Sonnet Echo II DV

Disclosure: Sonnet provided a review unit, but I was not compensated or sponsored, and I maintain complete editorial control.

Feature list

  • Dual PCIe slots with dedicated Thunderbolt buses
  • Each slot supports Thunderbolt pass-through for daisy-chaining
  • No power switch needed—it powers up/down automatically when Thunderbolt cables are connected
  • Built-in 400-watt power supply with two auxiliary power cables (75 watts each)
  • Can charge power-hungry laptops like my 16-inch MacBook M4 Pro via Thunderbolt
  • Features dual Noctua fans—the top shelf of PC cooling—rated at just 17 dBA
  • All-metal construction with no cheap plastic feel

The Sonnet Echo dv2 is a dual PCIe Thunderbolt enclosure with a unique advantage—each PCIe slot has its own dedicated Thunderbolt port. This means you get the full bandwidth of a complete Thunderbolt channel per card. Despite Sonnet explicitly stating that this case is not for GPUs, I still managed to wedge a single-slot GPU into it. It's not pretty, but it worked. You can also dongle the PCIe slots if you'd like a single cable experience, and it can deliver 100w to charge a laptop. Conversely you can also connect two computers to the Sonnet II DV allowing each computer to access a single PCIe slot.

Thunderbolt technology offers PCIe connectivity over a cable, but with limitations. A single Thunderbolt 4 connection provides approximately 2,880 MB/s of PCIe bandwidth. When multiple PCIe cards share a single Thunderbolt bus (as in most expansion chassis), they must compete for this bandwidth, potentially creating bottlenecks.

By providing each slot with its own dedicated Thunderbolt bus, the Echo II DV ensures that both cards can simultaneously utilize full bandwidth—provided your computer has Thunderbolt ports on separate buses. All Apple Silicon Macs meet this requirement, with each Thunderbolt port getting its own PCIe lanes.

The Echo II DV is Thunderbolt 3/4 and not 5. However, it does feature a modular Thunderbolt design, which represents perhaps its most forward-thinking feature. The Thunderbolt interfaces are implemented as daughtercards, which Sonnet refers to as "Thunderbolt upgrade cards" on their website. When I contacted Sonnet about potential Thunderbolt 5 upgrades, they confirmed that it would indeed be possible to swap the card and avoid buying a whole new enclosure. Ironically, this makes the Thunderbolt enclosure more upgradeable than Apple Silicon Macs—a critical consideration for professionals making long-term investment decisions.

sonnet open case

Inside is a modular design with two PCIe slots plus Cubo AR X3 Thunderbolt daughter cards. Interestingly, Sonnet refers to these as "Thunderbolt upgrade cards" on their website—suggesting potential future upgrades.

sonnet speed benchmark

Thunderbolt 5 is not PCIe 5.0 based, instead PCIe 4.0. A single thunderbolt port represents roughly a 4x PCIe slot. While PCIe 5.0 offers double the theoretical bandwidth of PCIe 4.0, real-world storage performance gains are much smaller. The Samsung 990 Pro (PCIe 5.0) vs. 980 Pro (PCIe 4.0) shows only about a 17% improvement in IOPS (47,419 vs. 40,580) according to Tom's Hardware metrics. Of course, NVMe storage will improve and be able to saturate PCIe 5.0 more over time; as of writing this, there are few practical applications where PCIe 4.0 speeds are prohibitive, let alone 3.0. All of this is a very roundabout way to say I don't see the Thunderbolt 4.0 speeds as much of an issue. I hope that a Thunderbolt 5.0 upgrade is around the corner, but for most users, it won't be a game changer.

Thunderbolt 3 vs. Thunderbolt 4

Thunderbolt 3 and Thunderbolt 4 are both high-speed connectivity standards developed by Intel, but they have some key differences. Thunderbolt 3 was introduced in 2015 and supports data transfer speeds of up to 40 Gbps, while Thunderbolt 4, introduced in 2020, maintains the same maximum speed but adds several enhancements.

One of the main differences is that Thunderbolt 4 requires support for USB4, which means it can work with a wider range of devices and peripherals. Thunderbolt 4 also mandates support for daisy-chaining up to six devices, while Thunderbolt 3 does not have this requirement. Additionally, Thunderbolt 4 includes improved power delivery capabilities, allowing for charging devices at higher wattages.

Feature Thunderbolt 3 Thunderbolt 4
Maximum Bandwidth 40 Gbps 40 Gbps
Display Support Minimum: Single 4K display
Maximum: Can support dual 4K @ 60Hz or single 5K		 Minimum: Dual 4K displays @ 60Hz or single 8K @ 30Hz
PCIe Data Transfer 16 Gbps minimum 32 Gbps minimum
Power Delivery Optional 100W charging Required 100W charging on at least one computer port
Security DMA protection optional Intel VT-d-based DMA protection required
Wake from Sleep Not guaranteed Required (PC can wake from sleep via connected Thunderbolt accessories)
Dock/Hub Support Limited downstream ports Support for docks with up to 4 Thunderbolt ports
USB4 Compatibility Compatible Compatible
Cable Length Limited certified length options Universal 40Gbps cables up to 2 meters
Connector Type USB-C USB-C


For all intents and purposes, the Sonnet Echo II DV is a Thunderbolt 4 device, as most of the action for Thunderbolt 4 exists on the controller side of things. It supports daisy chaining and power delivery.

Performance: Real-World Testing

Internal vs external benchmark sonnet echo dv

There's not a massive story when it comes to performance. Internal is faster than external, and that should not come as a surprise. Thunderbolt does have a higher protocol overhead; there is signal conversion between PCIe to Thunderbolt and latency due to distance. That said, it's in the ballpark of "close enough".

m4 pro vs M1 max speed benchmark

Comparing against the Thunderbolt 5 M4 Pro and Thunderbolt 4 M1 Max yeilded virtually no performance differences, with the M1 Max performing fractionally better. Amorphous tends to deliver inconsistent random tests and thus shouldn't be taken as exact but rather a rough estimate.

Being a Thunderbolt device, it's plug-and-play like USB. When I plugged it into my M1 Max, System Preferences showed six PCIe devices: four NVMe drives, two USB ports, and Ethernet from the McFiver card. For a secondary real-world test, for gigabit ethernet, I was able to achieve 450 MB/s read/writes to my Synology D923+ via the McFiver, identical to my Mac Pro 2019. The limitation is the NAS and not the card. 10 GBe is only 1250 MB/s max, something that was achievable even on Thunderbolt 2.

sonnet back of dv

As previously mentioned, one of the wackier use cases that the Sonnet Echo II DV supports is the ability to connect two computers. This is feasible as literally each PCIe slot is an independent Thunderbolt device, complete with it's own thunderbolt controller. This is a feature that I don't think many people will use, but it does work. You can connect two computers to the Sonnet Echo II DV and have each computer access a single PCIe slot. This could be useful for certain workflows.

One minor complaint I have is that the cabling extenrally doesn't doesn't include a fused cable akin to the Ivnaky Thunderbolt dock, that makes connecting and disconnecting easier, as it's simple as plugging in a singular cable. That said, Apple does not keep it's orientation and spacing of Thunderbolt ports uniform between laptops and desktops. It's an insignificant gripe but it's something as a laptop user I've become pretty spoiled by.

Ivanky dock

Not an eGPU case

installing an eGPU

It should be abundantly clear that the II DV is not a GPU case, with its single slot design, limited power capability, and cooling focus on low noise instead of maximum heat dissipation. However, this didn't stop me from trying. I was able to find a modern-ish single-slot GPU in the form of the AMD Radeon RX 6400. The card's specs are pretty abysmal, only 4 GB of VRAM, based on RNDA2 with the processor and RAM clocked at 2 GHz, a tiny 64-bit bus, 7 TFLOPs for FP16, making it performance wise roughly that of a GeForce 770 from 2013. However, it is bus-powered and is a single slot.

macOS does not have drivers for this GPU, so I was limited to Windows testing. It was moderately better than my Geekom MiniPC's very poor Intel Iris Xe

eGPU benchmark

So yes, you can jam a very shoddy GPU into this enclosure, but the sort of GPUs you can use are pretty abysmal. I wouldn't recommend it.

Market Alternatives: How the Echo II DV Compares

With several Thunderbolt expansion options available, it's important to understand how the Sonnet Echo II DV stacks up against alternatives. Here's a comparison of available solutions.

Sonnet's Own Product Line:

The Echo II DV positions itself as a premium offering in Sonnet's lineup. The price jump from the Echo Express III-D to the Echo II DV ($700 to $900) buys you dedicated Thunderbolt buses for each slot—a substantial advantage for bandwidth-intensive applications even though you get one fewer slot.

Sonnet Technologies

  • Sonnet Echo Express (three-slot with shared bus): $700
    • Advantages: Three PCIe slots, lower price point
    • Disadvantages: All slots share a single Thunderbolt bus, limiting combined bandwidth
  • Sonnet Echo Express SEL (single PCIe port): $300
    • Advantages: Single slot
    • Disadvantages: Single slot

OWC Solutions:

OWC's offerings tend to focus on storage expansion, with PCIe capabilities added as a secondary feature. None offer the dual Thunderbolt bus architecture that sets the Echo II DV apart.

  • OWC Mercury Helios 3S ($399)
    • Advantages: Lower price, includes a PCIe slot plus storage expansion bay
    • Disadvantages: Single thunderbolt bus
  • OWC Flex 8 ($649)
    • Advantages:Combines PCIe expansion with 8 storage bays
    • Disadvantages: Single Thunderbolt bus, shared bandwidth

Razer

  • Razer Core X ($399)
    • Advantages: Designed for GPUs, includes 650W power supply
    • Disadvantages: Single Thunderbolt bus, optimized for GPUs

This is by no means a comprehensive list, but alternatives exist ready to meet the consumers' needs at various price points. The Echo II DV is slotted at the upper echelon of external enclosures. It's not a cheap solution by any stretch. Its stiffest competition is from Sonnet itself, as I imagine for the majority of users; the Sonnet Echo Express probably represents the best value if they're looking to port over as much flexibility as possible. It brings a 3rd PCIe slot but relies on a shared bus. Most users rarely push more than one PCIe device at a time, and probably the only times users would feel the limits would be when transferring large files between SSDs (assuming both were in the enclosure).

Apple Mac Pro

Apple's Mac Pro starts at $6,999 and includes seven PCIe slots. However, these advantages come with significant caveats:

  1. The base model uses the M2 Ultra, which is now outdated compared to the M4 Pro/Max and M3 Ultra
  2. Internal slots don't support user-upgradable GPUs or CPU upgrades
  3. Total cost is significantly higher than a Mac Studio ($3,999) plus Echo II DV ($900)

Beyond the cost savings, the Mac Studio + Echo II DV route offers greater flexibility, as you can take your expansion cards to a future computer—something impossible with the Mac Pro's internal slots once the system is obsolete.

As of writing this, due to Apple's very odd market positioning of a M4 Max and M3 Ultra, for many users the M4 Max Mac Studio represents the better value, as the CPU is faster in single and low threaded tasks. In fact the M4 Max, only about 15% faster, granted the M3 Ultra offers a much more powerful GPU, and the ability to toss gobs of RAM into the system.

The $2k price jump probably isn't worth it for the majority of buyers, and the extra money could be spent on accessories like the Echo II DV to expand the storage well beyond Apple's meager offerings.

Conclusion: Rethinking Professional Mac Setups

After extensively testing the Sonnet Echo II DV, I've come to a conclusion that might have seemed heretical just a few years ago: for many professionals, the Mac Pro is no longer necessary.

The combination of Apple Silicon performance and external PCIe expansion creates a compelling alternative to the traditional workstation model. A Mac Studio, MacBook Pro, or even a Mac mini or MacBook Air paired with the Echo II DV, and you're getting most of the benefits of the Apple Silicon Mac Pro 2023 at a steep savings. Sadly, outside of a few exotic PCIe cards, there isn't much point to PCIe now that dGPUs have been sunsetted by Apple. Their switch to shared memory has yielded some impressive results for applications like AI, as VRAM can be dynamically assigned. However, in terms of raw performance, it hasn't materialized and plays deeply into Apple's hands for planned obsolescence.