PCIE 3.0 lspci -vv shows weird speed for intel arc gpu

English Hardware
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Obviously this isnt a super good use case for arc on an older motherboard with no resizable bar and such so I’m probably going to swap out for an AMD gpu but I’m a little confused what speed it is currently running at. The A380 is an 8 lane card and it kind-of looks like its running some weird pcie 1 lane at a weird speed. I don’t have any real PCIE type config options in bios other than power management.

Just wondering if anyone knows what might be going on

This might just be me misreading lspci output but I can see initially what looks like pcie 3.0 16 lanes at expected speed:

00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor PCI Express x16 Controller (rev 06) (prog-if 00 [Normal decode])
Subsystem: ASUSTeK Computer Inc. Device 8534
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- SERR- <PERR- INTx-
Latency: 0, Cache Line Size: 64 bytes
Interrupt: pin A routed to IRQ 24
Bus: primary=00, secondary=01, subordinate=04, sec-latency=0
I/O behind bridge: [disabled] [16-bit]
Memory behind bridge: f6000000-f73fffff [size=20M] [32-bit]
Prefetchable memory behind bridge: e0000000-f07fffff [size=264M] [32-bit]
Secondary status: 66MHz- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort+ <SERR- <PERR-
BridgeCtl: Parity- SERR+ NoISA- VGA+ VGA16+ MAbort- >Reset- FastB2B-
PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-
Capabilities: [88] Subsystem: ASUSTeK Computer Inc. Device 8534
Capabilities: [80] Power Management version 3
Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
Address: fee04004 Data: 0020
Capabilities: [a0] Express (v2) Root Port (Slot+), MSI 00
DevCap: MaxPayload 128 bytes, PhantFunc 0
ExtTag- RBE+
DevCtl: CorrErr- NonFatalErr- FatalErr- UnsupReq-
RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
MaxPayload 128 bytes, MaxReadReq 128 bytes
DevSta: CorrErr- NonFatalErr- FatalErr- UnsupReq- AuxPwr- TransPend-
LnkCap: Port #2, Speed 8GT/s, Width x16, ASPM L0s L1, Exit Latency L0s <256ns, L1 <8us
ClockPM- Surprise- LLActRep- BwNot+ ASPMOptComp+
LnkCtl: ASPM L1 Enabled; RCB 64 bytes, Disabled- CommClk+
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-

but then further down it looks like 2.5GT/s? for the A380 section:

03:00.0 VGA compatible controller: Intel Corporation DG2 [Arc A380] (rev 05) (prog-if 00 [VGA controller])
Subsystem: Device 172f:3941
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- SERR- <PERR- INTx-
Latency: 0, Cache Line Size: 64 bytes
Interrupt: pin ? routed to IRQ 27
Region 0: Memory at f6000000 (64-bit, non-prefetchable) [size=16M]
Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
Expansion ROM at 000c0000 [disabled] [size=128K]
Capabilities: [40] Vendor Specific Information: Len=0c <?>
Capabilities: [70] Express (v2) Endpoint, MSI 00
DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <64ns, L1 <1us
ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset+ SlotPowerLimit 0W
DevCtl: CorrErr- NonFatalErr- FatalErr- UnsupReq-
RlxdOrd- ExtTag+ PhantFunc- AuxPwr- NoSnoop+ FLReset-
MaxPayload 128 bytes, MaxReadReq 128 bytes
DevSta: CorrErr- NonFatalErr- FatalErr- UnsupReq+ AuxPwr- TransPend-
LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Exit Latency L0s <64ns, L1 <1us
ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp+
LnkCtl: ASPM L1 Enabled; RCB 64 bytes, Disabled- CommClk-
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 2.5GT/s, Width x1
TrErr- Train- SlotClk- DLActive- BWMgmt- ABWMgmt-
DevCap2: Completion Timeout: Range B, TimeoutDis+ NROPrPrP- LTR+
10BitTagComp+ 10BitTagReq+ OBFF Not Supported, ExtFmt+ EETLPPrefix-
EmergencyPowerReduction Not Supported, EmergencyPowerReductionInit-
FRS- TPHComp- ExtTPHComp-
AtomicOpsCap: 32bit- 64bit- 128bitCAS-
DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis- LTR+ 10BitTagReq- OBFF Disabled,
AtomicOpsCtl: ReqEn-
LnkCap2: Supported Link Speeds: 2.5GT/s, Crosslink- Retimer- 2Retimers- DRS-
LnkCtl2: Target Link Speed: 2.5GT/s, EnterCompliance- SpeedDis-
Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS-
Compliance Preset/De-emphasis: -6dB de-emphasis, 0dB preshoot

2

@butcherbird yes, it seems to be the norm for only what I assume is a non standard board. I see the same issue (A380) with non-standard motherboard… testing with oneapi, blender benchmark and memtest_vulkan all seem to show it working fine… I see encoding decoding working as well. I’m only using for offload in the test system, but have had it as the primary.

1 Like
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Awesome. Good to know thanks

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@butcherbird intel gputop will show it all working…

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@malcolmlewis I didn’t think to check that. I do see occasionally values in the 4000-5000MiB/s for read and write which is probably positive.

intel-gpu-top: Intel Dg2 (Gen12) @ /dev/dri/card1 - 2181/2444 MHz; 0% RC6; 200 irqs/s

  IMC reads:      993 MiB/s
 IMC writes:      425 MiB/s

     ENGINES     BUSY                                                    MI_SEMA MI_WAIT
   Render/3D   99.89%
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@butcherbird you could install the flatpak version of Mission Center (io.missioncenter.MissionCenter) as you user to see as well… but that should suffice for an indicator…

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