电子发烧友App
一、什么是PCIe4.0
PCIe全称PCI-Express，中文名称为高速串行总线。4.0是PCIe的一个版本，代表了系统总线的吞吐量，与CPU、GPU、显卡的数据传输速率息息相关。
可以把PCIe理解为一条管道，数据需要通过它进行传输。越高版本pcie，管道的内部空间就越大，支持传输的数据也就越高。
pcie4.0能够支持16GT/s的传输速率，以及最高32GB/s的带宽。相比于pcie3.0，使用pcie4.0的用户直观体验就是电脑的运算速率变快了。包括了文件的拷贝、软件的打开使用、游戏的加载等，都会因为pcie的升级而提高速率。
二、什么是U.2接口
U.2接口别称SFF-8639，是由固态硬盘形态工作组织(SSD Form Factor Work Group)推出的接口规范。U.2不但能支持SATA-Express规范，还能兼容SAS、SATA等规范。因此大家可以把它当做是四通道版本的SATA-Express接口，它的理论带宽已经达到了32Gbps，与M.2接口毫无差别。
在台北电脑展上，SF-8639接口将正式改名为U.2接口，跟目前的M.2接口对应起来了，因此U.2接口也是今后很有潜力的SSD接口。
硬盘主要接口及特点
M.2接口的固态硬盘主要优点在于体积小巧、性能出色，比较广泛的用于台式电脑、笔记本、超级本等便携设备中。而U.2接口则具备速度更快，2.5英寸更好的与目前SATA3.0接口固态硬盘兼容，适合主流笔记本、台式电脑，未来潜力较大。
总结，其实从直观表现上看，pcie4.0是虚拟的一种协议标准，而U.2接口是真实存在于现实世界中的硬件设备。
三、PCIe4.0 实测案例
启威测实验室提供PCIE3.0/4.0/5.0信号一致性测试验证，以下为PCIe4.0 实测案例：
PCIe4.0 项目比较多，本次测试的项目有：
① Transmitter Eletrical Compliance Test
② Transmitter Preset Test
③ Receiver Link Equalization Test
1、测试设备：
| 示波器 | Tektronix MSO73304DX |
| 误码仪 | Anritsu MP1900A |
| 探棒 | Tektronix TCA292D |
| CBB板 | PCIe4.0 Gen4 Compliance Base Board |
| ISI板 | PCIe4.0 Gen4 ISI Board |
2、测试数据：
1) Transmitter Eletrical Compliance Test
1.1 Lane0 Test for Gen4 Preset 7
• Overall Sigtest Result: Pass!
• Mean Unit Interval (ps): 62.5
• Min Time Between Crossovers (ps): 13.342501
• Data Rate (Gb/s): 16.0
• Max Peak to Peak Jitter: 27.081124 ps
• Total Jitter at BER of 10E-12: 30.994488 ps
Total Jitter at BER of 10E-12 Passes Sigtest Limits!
• Minimum eye width: 31.505512 ps
• Deterministic Jitter Delta-Delta: 10.503702 ps
Deterministic Jitter Delta-Delta Passes Sigtest Limits!
• Random Jitter (RMS): 1.456451 ps
Random Jitter (RMS) Passes Sigtest Limits!
• Minimum Transition Eye Voltage: -0.109627 volts
Minimum Transition Eye Voltage Passes Sigtest Limits!
• Maximum Transition Eye Voltage: 0.106947 volts
Maximum Transition Eye Voltage Passes Sigtest Limits!
• Composite Eye Height: 0.05818
• Composite Eye Location: 0.499
Composite Eye Height Passes Sigtest Limits!
• Extrapolated Eye Height: 0.042053
Extrapolated Eye Height Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Above Eye: 0.021271 volts
Minimum Transition Eye Voltage Margin Above Eye Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Below Eye: -0.023354 volts
Minimum Transition Eye Voltage Margin Below Eye Passes Sigtest Limits!
• Minimum Transition Eye Height: 0.067625 volts
1.2 Lane1 Test for Gen4 Preset2
• Overall Sigtest Result: Pass!
• Mean Unit Interval (ps): 62.5
• Min Time Between Crossovers (ps): 0.009861
• Data Rate (Gb/s): 16.0
• Max Peak to Peak Jitter: 31.429782 ps
• Total Jitter at BER of 10E-12: 33.410254 ps
Total Jitter at BER of 10E-12 Passes Sigtest Limits!
• Minimum eye width: 29.089746 ps
• Deterministic Jitter Delta-Delta: 13.038507 ps
Deterministic Jitter Delta-Delta Passes Sigtest Limits!
• Random Jitter (RMS): 1.44799 ps
Random Jitter (RMS) Passes Sigtest Limits!
• Minimum Transition Eye Voltage: -0.103688 volts
Minimum Transition Eye Voltage Passes Sigtest Limits
• Maximum Transition Eye Voltage: 0.102027 volts
Maximum Transition Eye Voltage Passes Sigtest Limits!
• Composite Eye Height: 0.035468
• Composite Eye Location: 0.499
Composite Eye Height Passes Sigtest Limits!
• Extrapolated Eye Height: 0.02508
Extrapolated Eye Height Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Above Eye: 0.015425 volts
Minimum Transition Eye Voltage Margin Above Eye Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Below Eye: -0.015217 volts
Minimum Transition Eye Voltage Margin Below Eye Passes Sigtest Limits!
• Minimum Transition Eye Height: 0.053642 volts
1.3 Lane2 Test for Gen4 Preset 8
• Overall Sigtest Result: Pass!
• Mean Unit Interval (ps): 62.5
• Min Time Between Crossovers (ps): 0.00019
• Data Rate (Gb/s): 16.0
• Max Peak to Peak Jitter: 29.85061 ps
• Total Jitter at BER of 10E-12: 32.966273 ps
Total Jitter at BER of 10E-12 Passes Sigtest Limits!
• Minimum eye width: 29.533727 ps
• Deterministic Jitter Delta-Delta: 9.820583 ps
Deterministic Jitter Delta-Delta Passes Sigtest Limits!
• Random Jitter (RMS): 1.645158 ps
Random Jitter (RMS) Passes Sigtest Limits!
• Minimum Transition Eye Voltage: -0.091297 volts
Minimum Transition Eye Voltage Passes Sigtest Limits!
• Maximum Transition Eye Voltage: 0.090553 volts
Maximum Transition Eye Voltage Passes Sigtest Limits!
• Composite Eye Height: 0.039969
• Composite Eye Location: 0.499
Composite Eye Height Passes Sigtest Limits!
• Extrapolated Eye Height: 0.02373
Extrapolated Eye Height Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Above Eye: 0.014598 volts
Minimum Transition Eye Voltage Margin Above Eye Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Below Eye: -0.015475 volts
Minimum Transition Eye Voltage Margin Below Eye Passes Sigtest Limits!
• Minimum Transition Eye Height: 0.053073 volts
1.4 Lane3 Test for Gen4 Preset 7
• Overall Sigtest Result: Pass!
• Mean Unit Interval (ps): 62.5
• Min Time Between Crossovers (ps): 0.519146
• Data Rate (Gb/s): 16.0
• Max Peak to Peak Jitter: 26.917085 ps
• Total Jitter at BER of 10E-12: 29.872554 ps
Total Jitter at BER of 10E-12 Passes Sigtest Limits!
• Minimum eye width: 32.627446 ps
• Deterministic Jitter Delta-Delta: 8.776463 ps
Deterministic Jitter Delta-Delta Passes Sigtest Limits!
• Random Jitter (RMS): 1.499476 ps
Random Jitter (RMS) Passes Sigtest Limits!
• Minimum Transition Eye Voltage: -0.085465 volts
Minimum Transition Eye Voltage Passes Sigtest Limits!
• Maximum Transition Eye Voltage: 0.087877 volts
Maximum Transition Eye Voltage Passes Sigtest Limits!
• Composite Eye Height: 0.047144
• Composite Eye Location: 0.499
Composite Eye Height Passes Sigtest Limits!
• Extrapolated Eye Height: 0.034929
Extrapolated Eye Height Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Above Eye: 0.017345 volts
Minimum Transition Eye Voltage Margin Above Eye Passes Sigtest Limits!
• Minimum Transition Eye Voltage Margin Below Eye: -0.017729 volts
Minimum Transition Eye Voltage Margin Below Eye Passes Sigtest Limits!
• Minimum Transition Eye Height: 0.058074 volts
1.5 Worst Non Transition Signal Eye
| Lane0-Gen4 | Lane1-Gen4 |
| Lane2-Gen4 | Lane3-Gen4 |
2) Transmitter Preset Test for Gen4
| Lane Name | Preset Name | PreShoot | De-Emphasis | Result |
| Lane0 | P0 Gen4 | 0.000 dB | -5.810 dB | Pass |
| P10 Gen4 | 0.000 dB | -9.258 dB | Pass | |
| P1 Gen4 | 0.000 dB | -3.370 dB | Pass | |
| P2 Gen4 | 0.000 dB | -4.533 dB | Pass | |
| P3 Gen4 | 0.000 dB | -2.444 dB | Pass | |
| P4 Gen4 | 0.000 dB | 0.000 dB | Pass | |
| P5 Gen4 | 1.952 dB | 0.000 dB | Pass | |
| P6 Gen4 | 2.462 dB | 0.000 dB | Pass | |
| P7 Gen4 | 3.792 dB | -6.373 dB | Pass | |
| P8 Gen4 | 3.466 dB | -3.448 dB | Pass | |
| P9 Gen4 | 3.427 dB | 0.000 dB | Pass | |
| Lane1 | P0 Gen4 | 0.000 dB | -5.791 dB | Pass |
| P10 Gen4 | 0.000 dB | -9.230 dB | Pass | |
| P1 Gen4 | 0.000 dB | -3.372 dB | Pass | |
| P2 Gen4 | 0.000 dB | -4.500 dB | Pass | |
| P3 Gen4 | 0.000 dB | -2.377 dB | Pass | |
| P4 Gen4 | 0.000 dB | 0.000 dB | Pass | |
| P5 Gen4 | 1.935 dB | 0.000 dB | Pass | |
| P6 Gen4 | 2.368 dB | 0.000 dB | Pass | |
| P7 Gen4 | 3.756 dB | -6.321 dB | Pass | |
| P8 Gen4 | 3.447 dB | -3.456 dB | Pass | |
| P9 Gen4 | 3.368 dB | 0.000 dB | Pass | |
| Lane2 | P0 Gen4 | 0.000 dB | -5.815 dB | Pass |
| P10 Gen4 | 0.000 dB | -9.232 dB | Pass | |
| P1 Gen4 | 0.000 dB | -3.357 dB | Pass | |
| P2 Gen4 | 0.000 dB | -4.478 dB | Pass | |
| P3 Gen4 | 0.000 dB | -2.389 dB | Pass | |
| P4 Gen4 | 0.000 dB | 0.000 dB | Pass | |
| P5 Gen4 | 1.904 dB | 0.000 dB | Pass | |
| P6 Gen4 | 2.329 dB | 0.000 dB | Pass | |
| P7 Gen4 | 3.733 dB | -6.307 dB | Pass | |
| P8 Gen4 | 3.405 dB | -3.465 dB | Pass | |
| P9 Gen4 | 3.327 dB | 0.000 dB | Pass | |
| Lane3 | P0 Gen4 | 0.000 dB | -5.744 dB | Pass |
| P10 Gen4 | 0.000 dB | -9.225 dB | Pass | |
| P1 Gen4 | 0.000 dB | -3.314 dB | Pass | |
| P2 Gen4 | 0.000 dB | -4.475 dB | Pass | |
| P3 Gen4 | 0.000 dB | -2.355 dB | Pass | |
| P4 Gen4 | 0.000 dB | 0.000 dB | Pass | |
| P5 Gen4 | 1.917 dB | 0.000 dB | Pass | |
| P6 Gen4 | 2.396 dB | 0.000 dB | Pass | |
| P7 Gen4 | 3.801 dB | -6.359 dB | Pass | |
| P8 Gen4 | 3.478 dB | -3.437 dB | Pass | |
| P9 Gen4 | 3.382 dB | 0.000 dB | Pass |
3) Receiver Link Equalization Test
| Test Items | Lane | Data Rate | Value | Units | Result | Specification |
| Add-in Card RX LEQ,100MHz | Lane0 | 16Gbps | 0 | unit | Pass | <=1 Error |
| Lane1 | 16Gbps | 0 | unit | Pass | <=1 Error | |
| Lane2 | 16Gbps | NA | unit | NA | <=1 Error | |
| Lane3 | 16Gbps | 0 | unit | Pass | <=1 Error |
3、PCIe4.0测试结果汇总：
| 测试项 | 信号速率 | 信号通道 | 测试结果 | 备注 |
| Transmitter Eletrical Compliance Test | 16Gbps | Lane0 | Pass | |
| Lane1 | Pass | |||
| Lane2 | Pass | |||
| Lane3 | Pass | |||
| Transmitter Preset Test | 16Gbps | Lane0 | Pass | |
| Lane1 | Pass | |||
| Lane2 | Pass | |||
| Lane3 | Pass | |||
| Receiver Link Equalization Test | 16Gbps | Lane0 | Pass | |
| Lane1 | Pass | |||
| Lane2 | NA | 无法进入loopback | ||
| Lane3 | Pass |
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