PCIe speed test

[the729 (Wu Tianji)]

我测试了ATI Stream Power Toy里面的PCIe Speed test，得到的结果不很令人满意。不知可能出问题的是哪里……

Gigabyte 790X, Phenom 9550, 蓝宝石 HD4870 1GB, DDR2 800 4GB
Ubuntu 8.10 amd64
结果是：
Peak CPU->GPU Bandwidth = 2.795 GB/sec [data size = 268435456 bytes]
Peak GPU->CPU Bandwidth = 3.007 GB/sec [data size = 8388608 bytes]

对比论坛上的相似机器：
Ubuntu 8.10 64-bit
phenom 9550+780v chipset + Radeon 4870 + 1066 MHz ddr2
Peak CPU->GPU Bandwidth = 5.160 GB/sec [data size = 134217728 bytes]
Peak GPU->CPU Bandwidth = 4.415 GB/sec [data size = 4194304 bytes]
以及：
Scientific Linux 5.2 64b
Phenom 9550, 8GB DDR2-800, 790X chipset, MSI K9A2-CF motherboard,
single HD4870/ 1GB
Peak CPU->GPU Bandwidth = 5.191 GB/sec [data size = 268435456 bytes]
Peak GPU->CPU Bandwidth = 3.539 GB/sec [data size = 8388608 bytes]

可以看出我们这机器的PCIe速度确实慢了不少。
lspci -vv的相关结果：
01:00.0 VGA compatible controller: ATI Technologies Inc RV770 [Radeon
HD 4870]
Subsystem: PC Partner Limited Device e850
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B- DisINTx+
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-
Latency: 0, Cache Line Size: 4 bytes
Interrupt: pin A routed to IRQ 2300
Region 0: Memory at d0000000 (64-bit, prefetchable) [size=256M]
Region 2: Memory at fdfe0000 (64-bit, non-prefetchable) [size=64K]
Region 4: I/O ports at de00 [size=256]
[virtual] Expansion ROM at fdf00000 [disabled] [size=128K]
Capabilities: [50] Power Management version 3
Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME
(D0-,D1-,D2-,D3hot-,D3cold-)
Status: D0 PME-Enable- DSel=0 DScale=0 PME-
Capabilities: [58] Express (v2) Legacy Endpoint, MSI 00
DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <4us, L1
unlimited
ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset-
DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
RlxdOrd+ ExtTag+ PhantFunc- AuxPwr- NoSnoop+
MaxPayload 128 bytes, MaxReadReq 128 bytes
DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
LnkCap: Port #0, Speed 2.5GT/s, Width x16, ASPM L0s L1, Latency L0
<64ns, L1 <1us
ClockPM- Suprise- LLActRep- BwNot-
LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk+
ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
LnkSta: Speed 2.5GT/s, Width x16, TrErr- Train- SlotClk+ DLActive-
BWMgmt- ABWMgmt-
Capabilities: [a0] Message Signalled Interrupts: Mask- 64bit+
Queue=0/0 Enable+
Address: 00000000fee0f00c Data: 4191
Capabilities: [100] Vendor Specific Information <?>
Kernel driver in use: fglrx_pci
Kernel modules: fglrx

可见其中的"MaxPayload 128 bytes"，不知问题是不是出在这里。