Real cluster vs. a pile of desktop cards
Both can add up to a big "GB" number on paper. Only one of them can actually run a single huge model.
| At a glance | Real cluster — DGX H100 | Pile of desktop cards — 6x RTX 6000 Ada |
|---|---|---|
| Total memory | 640GB | 288GB |
| Interconnect speed | ~900GB/s per GPU (NVLink) | Standard Ethernet/Wi-Fi — roughly 1,000x slower |
| Can run a single large model? | Yes | No |
| Support | One NVIDIA support contract | 6 individual card warranties |
| Approximate price | ~$200,000 | ~$40,800 |
A real cluster — e.g. DGX H100
- 8 H100 GPUs sit inside one chassis, wired by NVLink at up to ~900GB/s per GPU.
- Their 80GB memories act as one 640GB pool — a single model can be split cleanly across all 8.
- Built, tested, and sold by NVIDIA as one product, with one support contract.
A pile of desktop cards — e.g. 6x RTX 6000 Ada
- Each card lives in its own regular computer, connected only by ordinary ethernet or Wi-Fi — thousands of times slower than NVLink.
- Each card's 48GB of memory stays its own separate island; there's no hardware pooling them into one 288GB pool.
- A single huge model can't realistically split itself across them the way it can across a real cluster — at best you run several small, separate jobs.
The honest takeaway: 6 RTX 6000 Ada cards add up to 288GB on a spec sheet, which sounds like it beats a single H100. But that number is not honestly comparable to a real cluster's shared memory — the desktop pile can't act as one machine, so it can't run one model that's bigger than any single card in the pile.
A big model has to load as one piece in memory — you can't hand it half a brain. Qwen3 235B, one of the models this store advises on, needs about 282GB to load. Our pile of 6 RTX 6000 Ada cards adds up to 288GB on a spec sheet — technically more than enough. But that memory sits in 6 separate 48GB islands, and no single piece of it is bigger than 48GB. It's like having six half-full gas tanks instead of one full one: the total fuel is there, but no car can run on six disconnected tanks at once. A real cluster's NVLink wiring is what turns 8 separate 80GB tanks into one true 640GB tank — that's the only way the "GB" number on the spec sheet becomes a number you can actually use.