From: Marc Jones [mailto:firstname.lastname@example.org]
Sent: Thursday, July 17, 2008 4:28 PM
To: Myles Watson
Subject: Re: [coreboot] HT credits and the Opteron
Myles Watson wrote:
Anyone with detailed knowledge of (or more
manuals than I have for) the
I just noticed that the Nvidia ck804 reduces the amount of credits which
Opteron gives it (probably due to an errata.)
Does that mean that there
should be more credits available for the other HT links? Is buffer
per link or does the CPU share it all between all
the links? What if a
is disabled? Should you give its credits to the
In the BKDG for the Opteron it says that you shouldn't change the values
general, because software picks the right values,
but that's us. It
say how you should pick new values.
Thanks for the quick response.
I assume that you are talking about the XBAR buffer
Sorry. I should have been more clear. I was talking about 3.3.15: LDTi
Buffer Count Registers. Does your answer still apply?
The links are profiled by the designers and then
appropriate values are
assigned. There are some limitations in allocating the buffers so you
can't just take some form one place an use it somewhere else. For the
most part, you shouldn't run out of buffers in a typical system, so
nothing would be gained by adding more to a particular interface.
Generally, we should set what the factory bios sets since those settings
are validated. If a customer is building their own platforms we will
work with them to set appropriate values for their silicon.
Now that there is an open-source HT core from the University of Mannheim,
anyone could do this, but maybe most people will leave it alone.