To configure the size of the pre-allocated DMA buffer, add this line in the file SYSTEM.INI in the section [386Enh]:
More Info MS KB82711
DMABufferSize=64 (Default - 16 Range 1-256)
More Info MS KB82790
More Info MS KB124729
Note the above setting can also be configured by going to the "Control Panel" -> "System" -> "Device Manager", and expand the "System"-node, and select properties for "Direct Memory Access Controller", and select the tab "Settings" and set the "Reserve DMA buffer" to 64.