I have need to force 64-bit transactions on a 64-bit PCI bus 
from a PIII running NetBSD/1.4.2. This is in part to test a 64-bit PCI
card that we are building.

  I notice that bus.h has: 
 
#if 0      /* Cause a link error for bus_space_write_8 */ 
#define    bus_space_write_8     !!! bus_space_write_8 not implemented !!! 
#endif 
 
  will something like: 
       ((void)(*(volatile u_int64_t *)((h) + (o)) = (v))); 
 
  work? I realize that it may not be atomic. Are there Intel instructions 
for doing 64-bit I/O (I thought not). 

  My impression is that adjacent 32-bit writes should get coalesced into
a single 64-bit operation. 
 
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