Subject: Can't set up ISA DMA map with 64Mb RAM
To: None <tech-kern@netbsd.org>
From: Riaz <riazr@cat.co.za>
List: tech-kern
Date: 08/15/2000 15:17:24
Hello

We have NetBSD 1.4 (i386) with 4 of our PCI Video Capture Cards.
Our driver allocates 2972kb DMA memory (bus_dmamem_alloc)
for each of the Video Capture Cards ie 4 x 2972kb.

When we have 64Mb RAM, the "fdc0" driver fails with 
the error "can't set up ISA DMA map".
("uvm_pglistalloc" fails)

However if we use 32Mb RAM (or 48Mb or 96Mb or 128Mb), 
everything loads correctly.

(We have found the same results on various Gigabyte and Intel Motherboards)
 
-Does anyone know why 32Mb should work and not 64Mb?
-Could this have something to do with ISA can't DMA above 16Mb?
 and 15Mb (12Mb Video Capture Cards + 3Mb kernel) of first 16Mb is used
-If yes, what can we do as a work around?

Thanks in advance
Riaz Randeree