Re: PATCH: improved processor config for G3s

[Benjamin Herrenschmidt <bh40@calva.net>]

>
>The absence of broadcast might definitely harm, but first the support for
>store gathering in the MPC106 (Grackle) is quite poor:
>
>"For a stream of single-beat writes, the data for the first transaction is
>latched in the first buffer and the MPC106 initiates the transaction on
>the PCI bus. The second single-beat write is then stored in the second
>buffer. For subsequent single-beat writes, store gathering is possible if
>the incoming write is to sequential bytes in the same half cache line as
>the previously latched data. Store gathering is only used for writes to
>PCI memory space, not for writes to PCI I/O space. The store gathering
>continues until the buffer is scheduled to be flushed or until the
>processor issues a synchronizing transaction.

Well, that would help unaccelerated frame buffers (but are there any on
Grackle-based machines ?)


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