Slave DMA MapTransfer ordering

This is probably academic, since I'm guessing no one uses system
(slave) DMA anymore, but the DDK description of it says to call
MapTransfer _before_ setting up the device for the DMA operation.
Doesn't MapTransfer have to be called after the device is already set
up, since MapTransfer will actually cause the system DMA controller to
begin accessing the device?

David
Fri Oct 13 23:21:52 CDT 2006

Almost anyone who wants to program the floppy DMA would look at the IBM PC
Technical Reference from the days of the XT & AT. The BIOS code was given
that shows how it is done. Then you can look at the source for the drivers
in the DDK/WDK that actually do it under Windows NT/2000/XP/2003/Vista.
However, only the floppy would use system DMA anymore. Can you tell me why
it doesn't make any difference if the floppy still uses it instead of
another DMA method? I spent too many years playing with floppies, the
Smarty, & the FlashPaths.

<BubbaGump> wrote in message
news:b8lvi29flmiog69mr9kb7319bofas58rbh@4ax.com...
> This is probably academic, since I'm guessing no one uses system
> (slave) DMA anymore, but the DDK description of it says to call
> MapTransfer _before_ setting up the device for the DMA operation.
> Doesn't MapTransfer have to be called after the device is already set
> up, since MapTransfer will actually cause the system DMA controller to
> begin accessing the device?
>

Maxim
Sat Oct 14 14:21:10 CDT 2006

> MapTransfer _before_ setting up the device for the DMA operation.
> Doesn't MapTransfer have to be called after the device is already set
> up, since MapTransfer will actually cause the system DMA controller to
> begin accessing the device?

No. MapTransfer programs the DMA controller, so, it must be done before
starting the device. ISA DMA controller is a slave, it only operates if the
device asserts DRQ#, so, first the DMA controller must be set up, and only then
the device.

--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com

Maxim
Sat Oct 14 14:21:48 CDT 2006

> However, only the floppy would use system DMA anymore.

Ancient SoundBlasters of 90ies and ECP parallel port also use it.

--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com

David
Sat Oct 14 20:46:52 CDT 2006

I don't user either of those any more. Most of the motherboards today
include sound chips and while I do want two serial ports, I am happy if the
parallel port goes away. Soon, the floppy will only be a memory that will
only popup during nightmares. I still remember doing experiments trying to
get the controller to allow both floppy drives to be actively spinning at
once - no can do. Also trying to get a transfer rate greater than 350 kbps
is impossible even if 500 kbps is supposed to be the maximum.

"Maxim S. Shatskih" <maxim@storagecraft.com> wrote in message
news:eS%23q8X87GHA.3736@TK2MSFTNGP02.phx.gbl...
>> However, only the floppy would use system DMA anymore.
>
> Ancient SoundBlasters of 90ies and ECP parallel port also use it.
>
> --
> Maxim Shatskih, Windows DDK MVP
> StorageCraft Corporation
> maxim@storagecraft.com
> http://www.storagecraft.com
>

already5chosen
Sun Oct 15 08:35:39 CDT 2006


BubbaGump wrote:
> This is probably academic, since I'm guessing no one uses system
> (slave) DMA anymore, but the DDK description of it says to call
> MapTransfer _before_ setting up the device for the DMA operation.
> Doesn't MapTransfer have to be called after the device is already set
> up, since MapTransfer will actually cause the system DMA controller to
> begin accessing the device?

Intel wants to revive System DMA. Now they call it Intel I/OAT.