PROMPT
You see cache/memory latency, coherency traffic, attach-mode bandwidth on CXL Attach Modes. Walk through root cause and fix.

STRONG ANSWER
1. Names the layer and transaction identity.
2. Explains CXL.io, CXL.cache, and CXL.mem layer coherent and memory semantics on PCIe infrastructure.
3. Requests CXL mode table, coherency trace, memory window map.
4. Proposes one reduced sequence and one system regression.

WEAK ANSWER
Jumps to widening the interface, increasing FIFO depth, or blaming firmware without evidence.

CXL SUB-PROTOCOLS (share PCIe PHY)

CXL.io   : PCIe-like discovery, config, DMA            (Type 1/2/3)
CXL.cache: device caches host memory coherently        (Type 1/2)
CXL.mem  : host accesses device-attached memory         (Type 2/3)

Type 3 example: memory expander = mostly CXL.mem + CXL.io.

ROOT-CAUSE TREE — CXL Attach Modes

cache/memory latency, coherency traffic, attach-mode bandwidth looks wrong
        |
   reproducible?
     /        \
   no          yes
   |            |
 flaky env   same first transaction every time?
 / seed         /            \
              yes             no
               |               |
        protocol rule     timing/reset/PVT
        or config bug     or load-dependent

PCIe DEBUG TOP-DOWN

L0 link healthy?  -> credits OK?  -> TLP completes?  -> driver happy?

Skip a layer and you will mis-own the bug.

LINK DEGRADE EXAMPLE

target x4 Gen4  ---- ---- ---- ----
actual   x4 Gen4  ---- ---- ---- ----   (eval board)
actual   x1 Gen3  -                   (product board)

Package/SI often shows up as width downgrade, not hard fail.