Qwen 3.8 27B KV f16 vs q8_0 are not equivalents

I'm testing it since release, now with UD 3.0 in my AMD R9700 with ROCm, I always read everywhere that F16 and q8_0 for KV cache are essentially the same... well, I tested it and I can see differences. Some differences are minimal, F16 is more careful and detailed with structured and free output, thinking process almost all the time on point, and after 120k ctx can keep delivering as it was at < 50k (remembers). I saw some yt videos and posts with bad/mixed reviews, reading the details, q4_0 KV cache... ouch Anyone noticed this? Is this the case with just Qwen models? this is my config (I also used with Q6_K_M, I didn't notice much of a difference vs Q4_K_KL tbh): [*] ; device / offload device = ROCm0 n-gpu-layers = -1 n-cpu-moe = 0 flash-attn = on swa-full = true kv-unified = true kv-offload = true ; threads / misc threads = 24 threads-batch = 24 fit = off poll = 100 verbosity = 3 warmup = false log-timestamps = false jinja = true ; memory load-mode = mlock cache-ram = 40960 cache-type-k = f16 cache-type-v = f16 ; cache / slots cache-ram = -1 ctx-checkpoints = 32 checkpoint-min-step = 8192 parallel = 1 cont-batching = false image-min-tokens = 1024 image-max-tokens = 2048 ; ------------------------------------------------------------------------ [qwen3.8-27B] alias = coding-model,tool-model,planner-model,flash-model,vision-model,chat-model model = /root/models/unsloth/Qwen3.8-27B-GGUF/Qwen3.8-27B-UD-Q4_K_XL.gguf mmproj = /root/models/unsloth/Qwen3.8-27B-GGUF/mmproj-F16.gguf ; ctx-size = 262144 ctx-size = 184320 ; speculative decoding: MTP + ngram-mod spec-type = ngram-mod,draft-mtp spec-draft-p-min = 0 spec-draft-n-max = 3 spec-draft-type-k = f16 spec-draft-type-v = f16 spec-ngram-mod-n-match = 24 spec-ngram-mod-n-min = 48 spec-ngram-mod-n-max = 64 ; sampling (swap filter setParams) temp = 1.0 top-p = 0.95 top-k = 20 min-p = 0.0 presence-penalty = 0.0 repeat-penalty = 1.0 ; reasoning reasoning = on reasoning-format = deepseek reasoning-preserve = true ; reasoning-budget = 8192 ; chat-template-kwargs = {"preserve_thinking": true, "reasoning_effort": "medium"} chat-template-file = /root/models/chat_template.jinja submitted by /u/Felixls [link] [comments]

Source: r/LocalLLaMA | 2026-08-20