Firmware · cited only

BIOS settings for local AI on Radeon

What the firmware must get right before ROCm or llama.cpp sees a 32 GB card. Organized by chipset. Every sentence here is cited or marked not recorded. We do not invent a motherboard for local desktop.

Settings Chipsets Board notes Dual x8/x8 boards Hardware

Settings to look for

Cross-chipset. The chipset cards below only add official lane and memory-profile facts.

bar

Above 4G Decoding

Lets the firmware place a large GPU BAR in the MMIO window above 4 GB.

  • On modern 64-bit platforms the firmware allocates an MMIO aperture below 4 GB for 32-bit compatibility and one or more apertures above 4 GB for devices that need more space. [1]
  • ROCm’s BAR guidance says to enable the BIOS option named Above 4G Decoding, and to keep the high MMIO aperture inside the device physical-address limit (the docs use a 44-bit example with MMIO High Base / MMIO High Size). [1]
  • Two 32 GB cards plus a 256 GB host map a large prefetchable BAR. We have not measured a tok/s delta with Above 4G off on the local desktop. not recorded

bar

Resizable BAR / Smart Access Memory

AMD’s name for giving the CPU a full view of graphics memory. Menu labels vary by board.

  • AMD Smart Access Memory is described as giving a Ryzen CPU immediate, full access to Radeon graphics memory. [2]
  • AMD’s RDNA 4 UEFI note says Compatibility Support Module (CSM) mode disables advanced UEFI features, including AMD Smart Access Memory. [3]
  • The exact BIOS string (Re-Size BAR Support, Resizable BAR, Smart Access Memory) is vendor-specific. Record it on a board row; do not assume one label. not recorded
  • We have not measured llama.cpp or Strata tok/s with Resizable BAR on versus off on the R9700 rig. not recorded

boot

CSM off (UEFI only)

RDNA 4 and later graphics are UEFI-only in AMD’s support article.

  • Starting with AMD RDNA 4 (Radeon RX 9000 Series Graphics and later), only UEFI mode is officially supported. [3]
  • AMD says CSM emulates older BIOS behavior by disabling UEFI performance, security, and reliability features, and that Radeon graphics can lose Smart Access Memory when CSM is on. [3]
  • AMD’s steps are to enter the UEFI interface and disable Compatibility Support Module / CSM, typically under the Boot menu, using the motherboard manual if the label is not obvious. [3]
  • The Radeon AI PRO R9700 is an RDNA 4 workstation card (PCIe 5.0 x16). Treat it as in the RDNA 4-and-later UEFI-only set. [4]

pcie

PCIe slot generation, bifurcation, and the two-GPU split

CPU graphics lanes are 1×16 or 2×8 on the AM5 chipsets below. Matching width matters more than a mixed x16/x4 pair.

  • The R9700 ships as a PCIe 5.0 x16 card on AMD’s product page. [4]
  • AMD’s AM5 chipset table lists graphics as 1×16 or 2×8 (PCIe 5.0 on X870E and X670E; PCIe 4.0 on B650). That is the official CPU-direct split, not a chipset x4 leftover. [5]
  • Intel’s Z890 specification lists supported processor PCIe configurations as PCIe 5.0 1×16+1×4 or 2×8+1×4 or 1×8+3×4, plus PCIe 4.0 1×4. Chipset lanes on that page are PCIe 4.0, up to 24, in x1/x2/x4. [6]
  • ROCm on Radeon multi-GPU guidance requires identical PCIe lane width or bifurcation on the slots the GPUs use (x16+x16 or x8+x8). A mixed x16+x8 pair is listed as not recommended. [7]
  • The same ROCm page says to use CPU-connected slots and avoid chipset-connected slots, and to read the motherboard’s electrical map. An x16/x4 two-GPU layout is usually one CPU slot plus a chipset or leftover x4 — confirm on the board, do not assume. [7]
  • ROCm requires CPUs that support PCIe atomics (modern CPUs after first-generation Zen and Intel Haswell, on the Linux system-requirements page). Some consumer boards only expose atomics on the first slot. [8]
  • Which physical slots on a named board go x8/x8 versus x16/x4, and whether a Gen5 slot downtrains with two cards, stays a per-board note. not recorded

memory

Memory EXPO / XMP and four DIMMs

EXPO and XMP are overclock profiles. Four DIMMs are a different validation than two.

  • AMD EXPO (Extended Profiles for Overclocking) is AMD’s DDR5 overclocking-profile standard for Ryzen on socket AM5. [9]
  • AMD’s AM5 chipset table marks X870E, X670E, and B650 as supporting DDR5 memory overclocking with AMD EXPO. [5]
  • Intel XMP is Intel’s BIOS-enabled overclock profile for compatible DDR5/DDR4 modules on compatible Intel Core / Core Ultra platforms. [10]
  • EXPO and XMP are overclocking, not the JEDEC default. A two-DIMM kit profile is not a four-DIMM guarantee. Check the board QVL for the kit you actually bought. not recorded
  • local desktop has 256 GB DDR5. The motherboard model, DIMM count, and whether EXPO is enabled are not published. Do not invent a frequency. not recorded

iommu

IOMMU and SR-IOV

IOMMU is a BIOS-plus-kernel story. SR-IOV is documented for specific Instinct / PRO SKUs, not the R9700.

  • ROCm documents three Linux IOMMU modes — remapping (default; recommended for Radeon GPUs that need peer-to-peer DMA), passthrough (`iommu=pt`; recommended for Instinct and for Radeon GPUs that do not need P2P), and `iommu=off` (not recommended). [11]
  • ROCm’s BAR page also lists enabling the IOMMU (non-passthrough) as a way to keep device virtual I/O addresses inside physical-address limits. [1]
  • ROCm on Radeon multi-GPU notes IOMMU-related hangs and points at the multi-GPU application-hang write-up. BIOS on versus `iommu=pt` on a two-R9700 desktop is not measured here. [7] not recorded
  • SR-IOV BIOS enablement in current ROCm docs is written for specific SKUs (RDNA2 V620 is a documented example; W6800 is called unsupported there). The Radeon AI PRO R9700 is not on that SR-IOV list. [12]
  • ROCm’s Linux system-requirements virtualization table covers Instinct accelerators and selected Radeon PRO parts. Do not treat SR-IOV as a consumer R9700 feature. [8]

power

Power and C-states

Instinct cluster docs talk about C-states. That is not a measured R9700 desktop recipe.

  • AMD Instinct OS-tuning docs discuss restricting CPU C-states (`processor.max_cstate=0`, or disabling C2 after boot) when the BIOS has not already limited them, as a latency/responsiveness setting for Instinct systems. [13]
  • Those pages are Instinct system-acceptance guidance. We have not measured llama.cpp tok/s or hang rate with C-states on versus off on the local desktop. not recorded
  • The R9700 product page publishes 300 W TBP and a 750 W minimum PSU recommendation. That is electrical, not a C-state switch. [4]

power

Fan curves and PCIe ASPM

ASPM is a PCIe power-management feature. Fan curves are board firmware.

  • AMD Instinct kernel-parameter notes list `pcie_aspm=off` as a way to disable PCIe Active State Power Management, at the cost of slightly higher bus power, and call it recommended when prioritizing performance on those systems. [14]
  • That ASPM note is Instinct system-acceptance guidance. Effect on a desktop R9700 llama.cpp session is not measured. not recorded
  • Motherboard fan and pump curves are vendor BIOS or a vendor app. No local desktop fan curve is published. not recorded

By chipset

Official lane tables only. A chipset that can do 2×8 does not mean your board wired two GPU slots.

AM5 · AMD

AMD X870E

CPU graphics
1×16 or 2×8 PCIe 5.0
NVMe / GPP
1×4 PCIe 5.0 plus 4× PCIe GPP
Usable PCIe
44 total / 24 PCIe 5.0 (up to)
Memory profile
AMD EXPO (DDR5 memory overclocking enabled on the AM5 table)
USB4 on the table
Standard

Chipset row [5]

  • Official AM5 table — CPU graphics lanes are 1×16 or 2×8 at PCIe 5.0. That is the chipset capability, not a promise that every X870E board wires two full x8 GPU slots. [5]
  • Prefer that 2×8 CPU split over a second GPU in a chipset slot. Confirm the board map before you buy the second card. [7]
  • USB4 is listed as standard on X870E. That can consume CPU lanes on some boards — check the manual. [5]

No submitted board notes for this chipset yet.

AM5 · AMD

AMD X670E

CPU graphics
1×16 or 2×8 PCIe 5.0
NVMe / GPP
1×4 PCIe 5.0 plus 4× PCIe GPP
Usable PCIe
44 total / 24 PCIe 5.0 (up to)
Memory profile
AMD EXPO (DDR5 memory overclocking enabled on the AM5 table)
USB4 on the table
Optional

Chipset row [5]

  • Same official CPU graphics split as X870E — 1×16 or 2×8 PCIe 5.0 — on AMD’s AM5 table. [5]
  • USB4 is optional on X670E, not standard. Do not assume a USB4 header ate a GPU lane without the board diagram. [5]
  • Identical-width CPU slots still apply if you run two cards. [7]

No submitted board notes for this chipset yet.

AM5 · AMD

AMD B650

CPU graphics
1×16 or 2×8 PCIe 4.0
NVMe / GPP
1×4 PCIe 4.0 (PCIe 5.0 optional)
Usable PCIe
36 total / 0 PCIe 5.0 (up to)
Memory profile
AMD EXPO (DDR5 memory overclocking enabled on the AM5 table)
USB4 on the table
Not listed as standard on the AM5 table

Chipset row [5]

  • Official AM5 table — B650 CPU graphics are 1×16 or 2×8 at PCIe 4.0. The R9700 is a PCIe 5.0 x16 card and will train to the slot’s generation. [5]
  • B650E on the same AMD table is the Extreme variant with PCIe 5.0 graphics (1×16 or 2×8). Do not treat a B650 board as B650E. [5]
  • A second GPU on B650 still wants a CPU-direct x8/x8 pair, not a chipset leftover. Many B650 boards only wire one full GPU slot — that is a board fact, not a chipset promise. [7] not recorded

No submitted board notes for this chipset yet.

LGA 1851 (Intel Core Ultra Series 2 desktop) · Intel

Intel Z890

CPU graphics
Processor PCIe 5.0 — 1×16+1×4 or 2×8+1×4 or 1×8+3×4; processor PCIe 4.0 1×4
NVMe / GPP
Board-specific. Chipset contributes PCIe 4.0 lanes (x1 / x2 / x4), up to 24.
Usable PCIe
Chipset max 24 PCIe 4.0 lanes; DMI 4.0 ×8 to the CPU
Memory profile
Intel XMP (BIOS-enabled overclock profiles on compatible kits)
USB4 on the table
Not stated on the Z890 expansion table we cite; read the board.

Chipset row [6]

  • Intel’s Z890 specification lists those processor PCIe configs. A 1×16+1×4 split is a CPU leftover x4 (often storage), not “the chipset gave you a second x16.” [6]
  • Chipset lanes are PCIe 4.0, maximum 24, configurations x1/x2/x4. ROCm still says keep GPUs on CPU-connected slots of matching width. [6]
  • Intel XMP is the overclock-profile name on this platform. Four-DIMM XMP stability is kit- and board-specific. [10]
  • Intel BIOS labels for VT-d (IOMMU), Resizable BAR, and Above 4G Decoding vary. Record them on a board row. not recorded

No submitted board notes for this chipset yet.

Per-board notes

Community BIOS walkthroughs only — this table stays empty until someone files a cited firmware walk. Boards whose maker manuals document a CPU-lane x8/x8 split live on dual x8/x8 motherboards.

Empty

No board rows yet

When someone sends a cited BIOS walkthrough, it lands here — vendor, model, chipset, BIOS version, the label they actually saw, and an https source. Until then the chipset cards above are the only facts.

Submit in Hardware & Builds Contributor rules

How to add a row

What a submission must include

Post in the forum or send a patch to src/data/bios.yaml. Invented slot maps and unlabeled tok/s get dropped.

  • vendor (ASUS, MSI, Gigabyte, ASRock, …)
  • model and chipset id (x870e / x670e / b650 / z890)
  • BIOS version and date
  • slot map (which physical slots are CPU x16 / x8 / chipset)
  • the setting label you actually saw, the value, and an https citation or photo note
  • four-DIMM kit part number if you talk about EXPO/XMP

Sources

Official vendor and ROCm pages. Instinct C-state and ASPM notes are labeled as Instinct guidance on the cards above — not as measured desktop advice.

  1. BAR access limits and physical addressing for AMD GPUs — AMD ROCm
  2. AMD Smart Technologies (Smart Access Memory) — AMD
  3. UEFI-only Support for AMD Graphics Cards (RDNA 4 and later) — AMD
  4. AMD Radeon AI PRO R9700 product page — AMD
  5. AMD Socket AM5 Chipset — AMD
  6. Intel Z890 Chipset specifications — Intel
  7. mGPU setup and configuration (ROCm on Radeon) — AMD ROCm
  8. ROCm system requirements (Linux) — AMD ROCm
  9. AMD EXPO Technology for AMD Ryzen Processors for Socket AM5 — AMD
  10. Intel Extreme Memory Profile (XMP) — Intel
  11. Input-Output Memory Management Unit (IOMMU) — AMD ROCm
  12. AMD RDNA2 system optimization (SR-IOV BIOS notes) — AMD ROCm
  13. Instinct OS tuning (C-states and IOMMU) — AMD Instinct docs
  14. Instinct kernel parameters (pcie_aspm, max_cstate) — AMD Instinct docs
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