Computed

Qwen2.5 14B Instruct on a Radeon RX 7900 XTX

Yes, quantized. Q8_0 is the largest that fits, leaving room for 32k tokens of context.

Change the numbers →Qwen2.5 14B Instruct on every card Radeon RX 7900 XTX across every model

Verdict

Q8_0

22.1 GiB usable of 24 GB

Weights (Q4_K_M)

8.4 GiB

27.5 GiB at FP16 · 14.8B params · 6 of 6 quant rows are measured files

KV cache

192.0 KiB per token at FP16

48 layers × 8 KV heads × 128 dimensions

Speed ceiling

55 tok/s

960 GB/s ÷ bytes read per token

Every quant, against this card

Weight bytes are the size of the real published file wherever one exists — 6 of these6 rows are measured from bartowski/Qwen2.5-14B-Instruct-GGUF, the rest computed from the parameter count. Max context is what the KV cache can grow to in whatever memory the weights leave behind, capped at the 32k tokens this model was trained to address.

Bars are the weight bytes at each precision; the dashed line is the usable memory of a Radeon RX 7900 XTX. Drawn from the computed byte counts, not sketched.

Precision	Bits/weight	Weights	Source	Fits	Max context	Ceiling
FP16 / BF16	16.00	27.5 GiB	measured file	−5.4 GiB	—	9.3 tok/s offloaded
Q8_0	8.50	14.6 GiB	measured file	yes	32,768 (model cap)	55 tok/s
Q6_K	6.57	11.3 GiB	measured file	yes	32,768 (model cap)	70 tok/s
Q5_K_M	5.69	9.8 GiB	measured file	yes	32,768 (model cap)	79 tok/s
Q4_K_M	4.87	8.4 GiB	measured file	yes	32,768 (model cap)	91 tok/s
Q3_K_M	3.98	6.8 GiB	measured file	yes	32,768 (model cap)	107 tok/s

What the context actually costs

The KV cache is 2 · layers · kv_heads · head_dim bytes per token per element — 2 · 48 · 8 · 128 · 2 B = 192.0 KiB. It depends on the key/value head count, not the attention-head count and not the parameter count. This model shares 8 KV heads across 40 query heads, which divides the cache by 5 against multi-head attention.

Context	KV cache (FP16)	KV cache (8-bit)	Plus Q4_K_M weights
4,096	768 MiB	384 MiB	9.1 GiB
8,192	1.5 GiB	768 MiB	9.9 GiB
32,768	6.0 GiB	3.0 GiB	14.4 GiB

The speed ceiling, and where it comes from

Generating one token reads every active weight from memory once. At Q8_0 that is 14.6 GiB, plus a pass over the KV cache. A Radeon RX 7900 XTX moves 960 GB/s (384-bit × 20 Gbps), so the arithmetic ceiling is 55 tok/s. Treat it as a bound, not an estimate: attention overhead, kernel launches and imperfect memory access keep real runtimes at roughly 60–80% of it, and nothing pushes past it.

Where these numbers come from

The model

Parameters: 14,770,033,664
Layers: 48
Attention / KV heads: 40 / 8
Head dimension: 128
Trained context: 32,768
Checkpoint as published: 27.5 GiB

Read from Qwen/Qwen2.5-14B-Instruct. The parameter count is the Hub's own total over the tensor shapes, not a figure taken from the model's name.

The accelerator

Memory: 24 GB GDDR6
Bandwidth: 960 GB/s
Bus: 384-bit × 20 Gbps
Assumed usable: 92% → 22.1 GiB

Capacity and bandwidth from the vendor's specification. The bandwidth figure is checked against the bus width and data rate it derives from. The usable fraction is an assumption, not a spec: a driver context, compute workspace and any attached display come out of the same pool before a weight is loaded.

Questions this pairing answers

How much VRAM does Qwen2.5 14B Instruct need?

27.5 GiB for the weights at FP16 — 14.8B parameters at two bytes each — and 8.4 GiB at Q4_K_M. The KV cache is on top of that and is not a fixed number: this model spends 192.0 KiB per token of context, so 8,192 tokens costs a further 1.5 GiB. A Radeon RX 7900 XTX makes 22.1 GiB of its 24 GB available on the assumption below.

Can a Radeon RX 7900 XTX run Qwen2.5 14B Instruct?

Yes, quantized. Q8_0 is the largest that fits, leaving room for 32k tokens of context. That is the weights and the KV cache together, against 22.1 GiB of usable memory.

How fast will Qwen2.5 14B Instruct run on a Radeon RX 7900 XTX?

No faster than 55 tokens/second at Q8_0, and in practice below it. Decoding is memory-bound: every token reads all 14.6 GiB of weights plus the cache, and this card moves 960 GB/s. That division is the ceiling — no kernel, runtime or driver beats it, and a real runtime typically reaches 60–80% of it.

Why does the context length change how much memory Qwen2.5 14B Instruct needs?

Because the KV cache holds one key and one value vector per token, per layer, for the whole conversation, and it is allocated separately from the weights. This model has 48 layers and 8 key/value heads of 128 dimensions, shared across 40 query heads — grouped-query attention, which divides the cache by 5. That works out at 192.0 KiB per token. Parameter count tells you nothing about this number.

The same model on a different card

A different model on the same card

All 62 models on Radeon RX 7900 XTX →

Method and limits. Weight bytes are the byte size of the real published file wherever one exists, and the model's exact parameter count times the published llama.cpp bits-per-weight where it does not. That distinction is on every row above and it matters at both ends: a sub-1B model's Q4_K_M file runs a third larger than the nominal figure because k-quants keep its embedding tables at higher precision, and an already-4-bit release cannot be quantized upward at all. The KV cache is 2 · layers · kv_heads · head_dim · bytes per token, summed over layers with each sliding-window layer capped at its window. The speed figure is a roofline bound, not a benchmark: bandwidth divided by bytes read per token, which no runtime exceeds and every runtime falls short of. The usable fraction of card memory is an assumption: 92% here, which is what this lane assumes for a dedicated card — the other class assumes 75%, so it is not one number applied to every device. That is the only assumed input on this page; every other figure is computed from the model config and the card's published specification. Nothing on this page is written by a language model. Architecture from the model's published config, fetched 2026-08-07.