Re: PCI-e x1 or PCI-X 133?
- From: "Folkert Rienstra" <see_reply-to@xxxxxxxx>
- Date: Mon, 2 Jul 2007 21:14:46 +0200
"Michael Baeuerle" <michael.baeuerle@xxxxxxx> wrote in message news:7n3il4-7m1.ln1@xxxxxxxxxxxxxxxxxxx
Folkert Rienstra wrote:
Michael Baeuerle wrote:
Folkert Rienstra wrote:
Michael Baeuerle wrote:
One PCIe lane is limited to 250MByte/s (full duplex in both directions),
2.5 Gb/s actually, per direction.
Yes, but that raw 313MByte/s
What raw 313 MB/s. It's 2.5 Gb/s.
of the physical layer can transfer a maximum of 250MByte/s payload
due to the 8B/10B encoding.
Whatever. It's 2.5 Gb/s, period.
Yes it is, to compare with other serial systems I would use that value too.
Any conversion in bytes is confusing and should be avoided as it has no
meaning unless stripped from all overhead.
No, because most other overheads like address transfers are present in
parallel PCI too, but not this one.
Neither does it have serial protocol (to replace the parallel bus protocol).
I have taken 250MByte/s per lane to compare with parallel PCI
transferrates like "132MByte/s" because parallel PCI transfers Bytes
with no clock recovery overhead over the physical layer. Therefore
encoding overhead of the physical layer should be subtracted and the
result converted to Byte/s for PCIe to do this comparison.
There still is the serial protocol to subtract.
Doing so is IMHO a fast and fair compromise.
To strip all overheads would be the better solution, but who can do this
without reading (that means buying) the standard?
Which still means that you must have an inkling of what's in there.
If you don't then you're just hoping that it is "a fair compromise".
^^^^^^^^^^^^^^^^^^^^^^^^PCI-X is half-duplex but gives you at least 532MByte/s.
Again, what PCI-X.
The minimum configuration: 64Bit/66MHz.
Well, it 's not.
[...]
AFAIK every PCI-X card or bus itself must be 3.3V and 64Bit (and must at
least support 66MHz).
"PCI-X TECHNOLOGY OVERVIEW
PCI-X enables the design of systems and devices that can operate at bus
frequencies of up to 133 MHz using a 64-bit or 32-bit bus width, a signifi-
cant improvement in performance beyond that of conventional PCI systems."
"Adapters
Like conventional PCI adapters, PCI-X adapters can implement a 64-bit
interface or a 32-bit interface. The two possible frequencies and two data
width interfaces give a total of four possibilities for adapter design. This
flexibility built into the PCI-X specification allows adapter designers to meet
customer needs with varying combinations of high performance, ease of design,
and cost."
source: PCI-X: An Evolution of the PCI Bus
So no.
Accepted, the PCI-X 2.0 FAQ even specify a 16Bit bus width for embedded
applications.
And low profile PCI and mini PCI and .......
The two possible frequencies are 66 and 133MHz
Oh? AFAICT that is 1.0, not 2.0.
because 100MHz seems to be an inofficial frequency.
It's a downward compatible frequency for X133 cards.
(And presumably also for faster cards).
.
Micha
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