On Sun, Jul 16, 2000 at 08:11:28PM -0700, Jason R Thorpe wrote:

 > ACTUALLY....
 > 
 > I just double-checked the manual, to be extra sure, and it says,
 > in section 9.5.2.9:
 > 
 > 	If an ISDN transmit DMA pointer crosses a page boundary,
 > 	the transmit buffer pointer is loaded into the transmit
 > 	pointer, and an interrupt is set.  This directs software
 > 	to reload the buffer pointer.  If the buffer pointer is
 > 	empty, the DMA is turned off because an invalid address
 > 	was loaded into the pointer, and another interrupt is
 > 	set siognaling overflow.  A buffer pointer may be empty
 > 	because it was never written to or has not been written
 > 	to since the last page crossing.
 > 
 > Note, "page size".  I suspect the IOASIC detects page size by how it's
 > wired to the bus.

And, ACTUALLY again...

Section 7.7: ISDN Transmit DMA Buffer Pointer

	This is the address to be loaded into the ISDN DMA Pointer
	when the Pointer reaches a page (4 KB) boundary.  This
	register is undefined at power up and must be loaded with
	the appropriate vcalue before DMA.

So, yah, looks like it is really 4K, even on Alpha.  (Sorry, I'm kind
of thinking aloud here :-)

-- 
        -- Jason R. Thorpe <thorpej@zembu.com>