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Breaking the Box: Why Your Gen5 Performance Benchmark Must Now consider your platforms External PCIe Fabric

For decades, the benchmark for maximum PCIe performance was confined to the server chassis; namely, what kind of devices can be hosted directly by the server itself. If your accelerator was installed internally (into the designated add-in-slot/riser) the speed was, more or less, guaranteed. With the rise of AI and HPC composability, this paradigm has been broken.


Historically, moving a GPU or high-speed storage outside the server chassis resulted in a massive performance penalty. The external cables were slow, signals were weak, and you had to use "tunneling" protocols (like Thunderbolt) which bottlenecked transfer speeds. Because of this, engineers were forced to cram everything into one server, leading to:

· Overheating: Too many hot GPUs/accelerators in one small box.

· Wasted, Fixed Resources: Accelerator resources were tied to their host. If the server didn't employ its GPU on any given day, that expensive card sat idle because it was physically "locked" inside that specific machine.


The New Reality: "AI & HPC Composability"


Composability (or Composable Disaggregated Infrastructure) is the ability to treat hardware like Lego bricks. Instead of a GPU being "married" to one server, it lives in its own external enclosure (like the RocketStor 8631D) and can be "composed" or assigned to any server that needs it via a high-speed cable (CopprLink-CDFP, in the case of the RocketStor 8631D).

 

The New Bottleneck: The Host-Out Connection


The challenge with external Gen5 x16 connectivity is not the physical hardware – several adapters, cables and connectors are already in deployment for such purposes. Rathe, it is about how such hardware operates. Making the most of your accelerator hardware means guaranteeing that a dedicated, non-tunneled 64GB/s signal pathway is available between the system and external devices.


· Internal PCIe: The signal travels mere centimeters, guaranteeing the expected bandwidth.

· External PCIe (conventional/legacy approach): Using non-dedicated or tunneled protocols (such as Thunderbolt), the PCIe signal is compressed, multiplexed with other data (such as video), and suffers from high latency and reduced throughput.

 

HighPoint’s Rocket 7634D was purposed engineered to address these issues.  This essential Host Interface Card (HIC) is designed to ensure that the platform’s external PCIe connectivity performs just as fast, and just as reliably, as the internal slots.


The Rocket 7634D resolves this by establishing a dedicated, high-speed PCIe pathway from the host CPU directly to the external port. It acts as a trusted Host Bridge, ensuring that the full x16 lanes of bandwidth are reserved and delivered with minimal overhead.


Why Internal Benchmarks No Longer Apply


If your HPC architecture relies on external GPUs, simply benchmarking the target accelerator card using a conventional internal PCIe slot the host is essentially meaningless. You must measure the effective End-to-End Throughput of your external PCIe fabric – the cable, adapter and connector, and how these devices will interact with the host CPU.


The Rocket 7634D is the only component that can guarantee the host-side fidelity needed to make the external connection a valid benchmark point. It unique PCIe switching architecture, external CDFP connectivity and PCI-SIG CopprLink compliant technology ensures your external accelerators have a full x16 lanes of bandwidth at their disposal – an absolute requirement for AI, deep learning, simulation and other performance hungry HPC workflows. The Rocket 7634D has transformed external PCIe expansion into a fully viable component of your high-tier compute fabric.


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