PCIe bus Max_Read_Request_Size Max_Payload_Size

最新推荐文章于 2025-03-10 11:07:25 发布

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最新推荐文章于 2025-03-10 11:07:25 发布

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本文探讨了PCI Express (PCIe) 中Max_Read_Request_Size与Max_Payload_Size的设置原则及交互作用。当Root Complex (RC) 的Max_Read_Request_Size小于Endpoint (EP) 时的处理方式，以及如何合理设定这两个参数。

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1) If the Max_Read_Request_Size of the RC is less than the EP, Now i have a transaction from EP to RC with the Max_Read_Request_Size equal to EP, what will happen?
2) In general ,how to design the value of the Max_Read_Request_Size and Max_Payload_Size between the EP and RC?

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question 1: RC will response EP request will multiple TLP, each TLP length will not exceed max_payload_size;
question 2: normally the max_payload_size is 256B or 128B, (256 is better), max_read_request_size is much larger that max_payload_size, such as 2K/4K;

Please ref:
1, PCIe 3.0 spec;
2, baidu search: “PCIe Max Read Request Size”, “PCIe Max Payload Size”
http://www.xilinx.com/support/answers/36596.html
http://mt.sohu.com/20161110/n472770654.shtml
http://blog.sina.com.cn/s/blog_6472c4cc0102dse9.html
3, buy this book: http://item.jd.com/11346986.html <PCI Express体系结构导读>
4, read this blog: http://blog.sina.com.cn/sailingxr