AMD's Instinct line has two parts people compare most: the MI300X, which has been rentable for a while, and the MI355X from the newer CDNA 4 generation. Both are about memory first. The question is whether the extra generation is worth the harder availability and the same software caveat.
Specs side by side
- MI300X (CDNA 3): 192 GB of HBM3 and about 5.3 TB/s of memory bandwidth. Around 750 W.
- MI355X (CDNA 4): 288 GB of HBM3E and about 8 TB/s of memory bandwidth, with FP4 and FP6 support added. Liquid-cooled and in the 1,400 W range.
- MI350X is the air-cooled sibling of MI355X with a lower power budget.
The headline is memory. 288 GB lets a single GPU hold models that need two MI300X or three H100, which simplifies serving of very large models. The FP4 and FP6 support is the other change, and it is what makes the newer part a Blackwell competitor rather than a Hopper competitor.
The software catch
AMD runs on ROCm, not CUDA. PyTorch, vLLM and the major frameworks support it, but custom CUDA kernels, some quantization libraries and certain attention implementations need a port or a check. Before you move a workload, run it on one MI300X hour. That test costs little and answers the question the spec sheet cannot.
Where to rent AMD today
MI300X is the part that appears in on-demand catalogs. See the MI300X price per hour and compare it with H100 and H200. MI355X capacity is mostly early, reserved or quote-based, so we do not rank it as an hourly row until a provider publishes an on-demand price.
Which one should you pick
- Model fits in 192 GB and your stack runs on ROCm: MI300X is the cheaper way into AMD.
- You need one-GPU capacity above 192 GB, or FP4 serving on AMD: MI355X, if a provider has it.
- You depend on CUDA-only tooling: stay on NVIDIA. See H100 vs H200 vs B200.
- Check memory fit first with the VRAM fit tool.
FAQ: MI355X and MI300X
How much VRAM does MI355X have?
288 GB of HBM3E, against 192 GB of HBM3 on MI300X.
Can I rent MI355X by the hour?
Availability is limited and often quote-based. MI300X is the AMD GPU you can rent on demand today.
Is MI300X cheaper than H100?
It depends on the provider and the hour. Compare the live on-demand rows on the MI300X and H100 pages, and weigh the ROCm porting cost.
Does MI355X run CUDA code?
No. It uses ROCm. Most PyTorch workloads port easily, custom CUDA kernels may not.
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