EISA/ISA DMA limits for >16MB, is this supported?

EISA/ISA DMA limits for >16MB, is this supported?

Post by Richard Shetr » Tue, 22 Mar 1994 00:03:42



I have an EISA motherboard, but all my current controller cards are
ISA.  I expect to add more then 16MB of memory before upgrading the
controller cards to EISA cards.  I did a quick look in both the FAQ and
some of the kernal stuff, but no where did I see anything like the
sysvr4 DMAMAXPAGE parameter that tells sysvr4 to restrict DMA to memory
below 16MB.

Is there a parameter like this in linux?  Can this be done on a per
controller basis, ie EISA disk, but ISA ethernet and serial cards?

 
 
 

EISA/ISA DMA limits for >16MB, is this supported?

Post by Eric Youngda » Wed, 23 Mar 1994 00:45:33



>I have an EISA motherboard, but all my current controller cards are
>ISA.  I expect to add more then 16MB of memory before upgrading the
>controller cards to EISA cards.  I did a quick look in both the FAQ and
>some of the kernal stuff, but no where did I see anything like the
>sysvr4 DMAMAXPAGE parameter that tells sysvr4 to restrict DMA to memory
>below 16MB.

        You do not need to do this.  The low level scsi drivers that do DMA all
know whether they suffer from the 16Mb limitation or not, and they all do the
right thing if you have more than 16Mb.

-Eric

--
"The woods are lovely, dark and deep.  But I have promises to keep,
And lines to code before I sleep, And lines to code before I sleep."

 
 
 

EISA/ISA DMA limits for >16MB, is this supported?

Post by Mark Lo » Wed, 23 Mar 1994 01:31:37




>>I have an EISA motherboard, but all my current controller cards are
>>ISA.  I expect to add more then 16MB of memory before upgrading the
>>controller cards to EISA cards.  I did a quick look in both the FAQ and
>>some of the kernal stuff, but no where did I see anything like the
>>sysvr4 DMAMAXPAGE parameter that tells sysvr4 to restrict DMA to memory
>>below 16MB.

>    You do not need to do this.  The low level scsi drivers that do DMA all
>know whether they suffer from the 16Mb limitation or not, and they all do the
>right thing if you have more than 16Mb.

Would this even be a concern for an EISA motherboard?  Surely EISA motherboards
do not include exactly the same DMA limitation as ISA motherboards?  As I recall
the limitation was in the 8237 (?) Intel DMAC chips on the motherboard.
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