Looking at mptlinux-3.03.02-src.tar.gz, mptbase.c, mpt_attach() I see:

        /* 1030 Chip Fix. Disable Split transactions
         * for PCIX. Set MOST bits to zero if Rev < C0( = 8).
         */
        pci_read_config_byte(pdev, PCI_CLASS_REVISION, &revision);
        if (revision < C0_1030) {
            pci_read_config_byte(pdev, 0x6a, &pcixcmd);
            pcixcmd &= 0x8F;
            pci_write_config_byte(pdev, 0x6a, pcixcmd);
        }

and naturally this card is a revision 7. I haven't seen a similar work
around in the NetBSD source (I've been looking at /sys/dev/{pci,ic}/mpt*).
BTW there are quite a few like that for the fibre channel cards.

Cheers,

Patrick