Re: HARI: Question regarding byte (column?) versus word striping
I believe you are missing the point of how word striping works.
As the number of lanes scales up, word striped data still uses
ONLY ONE WORD to be added/deleted for clock tolerance compensation.
That is, for n lanes, byte striping must delete n characters (ie,
a column) while word striping must delete only 4 characters (ie,
a word) from any one of the n lanes.
Without the constraint that the packet begin in a particular lane,
I believe that the IPG is CONSTANT for word striping, but must
grow linearly with the number of lanes for byte striping.
[Please note that the number of bytes (characters) in a "word"
in word striping is chosen to span the expected skew, yielding
its great simplicity of implementation. For HARI, it is merely
coincidence that the word size is the same as the number of lanes.
The word size and the number of lanes are independent things.]
I appreciate your comments on this issue, and I agree completely.
Please let me know if I've missed anything above, or if I need to
improve on my explanation.
Rich Taborek wrote:
> When Hari is scaled to higher speeds, Column-Striping can function with a
> smaller IPG than can Word-Striping. Two requirements of the IPG are:
> 1) Link synchronization - commas required
> 2) Clock tolerance compensation - insert/remove protocol required
> Column-Striping requires only a single column of commas (K) for link
> synchronization and utilizes a single column of skips (R) for clock tolerance
> compensation. The minimum IPG size based on starting a new packet in lane 0 is
> 3n, where n=number of lanes. That's one n for the K column, another for the R
> column and a third possibly complete column containing the End-of-Packet
> delimiter plus pad characters.
> Word-Striping uses words containing commas which may be inserted/deleted during
> the IPG. The minimum IPG size is 5n, where n=number of lanes. That's 4n for 4
> deletable Idles and one more word containing the End-of-Packet delimiter plus
> pad characters.
> Best Regards,
Mike Jenkins Phone: 408.433.7901 _____
LSI Logic Corp, ms/G715 Fax: 408.433.7461 LSI|LOGIC| (R)
1525 McCarthy Blvd. mailto:Jenkins@xxxxxxxx | |
Milpitas, CA 95035 http://www.lsilogic.com |_____|