Messages in this thread Patch in this message | | | Date | Wed, 14 Oct 2009 10:42:22 +0200 | From | Stefan Assmann <> | Subject | GT/s vs Gbps for PCIe bus speed |
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Hi all,
I'm really confused about GT/s¹ vs Gbps². The PCIe 2.0 Base Spec (rev 0.9) on page 34, section 1.2 speaks of "Signaling rate - [...] For the first generation of PCI Express technology, there is only one signaling rate defined, which provides an effective 2.5 Gigabits/second/Lane/direction of raw bandwidth." but later in the document it purely speaks of 2.5 GT/s.
If I understand this correctly it means the following: PCIe has a raw bandwidth of 2.5 Gbps (or 5.0 Gbps, whatever) but because of the "8b/10b" encoding the effective bit rate is only 2.5 Gbps * (8/10). So it's called 2.5 GT/s to explicitly say this is raw bandwidth.
IMHO this is rather confusing, as most people don't know what GT/s means.
So I'd suggest the following change:
diff --git a/drivers/pci/hotplug/pci_hotplug_core.c b/drivers/pci/hotplug/pci_hotplug_core.c index 0325d98..75ef3d7 100644 --- a/drivers/pci/hotplug/pci_hotplug_core.c +++ b/drivers/pci/hotplug/pci_hotplug_core.c @@ -86,8 +86,8 @@ static char *pci_bus_speed_strings[] = { "66 MHz PCIX 533", /* 0x11 */ "100 MHz PCIX 533", /* 0x12 */ "133 MHz PCIX 533", /* 0x13 */ - "2.5 GT/s PCI-E", /* 0x14 */ - "5.0 GT/s PCI-E", /* 0x15 */ + "2.5 Gbps PCI-E", /* 0x14 */ + "5.0 Gbps PCI-E", /* 0x15 */ };
#ifdef CONFIG_HOTPLUG_PCI_CPCI
¹ Gigatransfers/second ² Gigabits/second
Stefan -- Stefan Assmann | Red Hat GmbH Software Engineer | Otto-Hahn-Strasse 20, 85609 Dornach | HR: Amtsgericht Muenchen HRB 153243 | GF: Brendan Lane, Charlie Peters, sassmann at redhat.com | Michael Cunningham, Charles Cachera -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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