PCI Express Performance and Data Transfer Efficiency
As of May 2003, no realistic performance and efficiency numbers were available. However, Table 2-3 shows aggregate bandwidth numbers for various Link widths after factoring the overhead of 8b/10b encoding.
| PCI Express Link Width | x1 | x2 | x4 | x8 | x12 | x16 | x32 |
|---|---|---|---|---|---|---|---|
| Aggregate Bandwidth (GBytes/sec) | 0.5 | 1 | 2 | 4 | 6 | 8 | 16 |
DLLPs are 2 doublewords in size. The ACK/NAK and flow control protocol utilize DLLPs, but it is not expected that these DLLPs will use up a significant portion of the bandwidth.
The remainder of the bandwidth is available for TLPs. Between 6-7 doublewords of the TLP is overhead associated with Start and End framing symbols, sequence ID, TLP header, ...
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