N2_PSR
return inb(card->io + N2_PSR) & PSR_PAGEBITS;
u8 psr = inb(card->io + N2_PSR);
outb((psr & ~PSR_PAGEBITS) | page, card->io + N2_PSR);
outb(inb(io + N2_PSR) | PSR_DMAEN, io + N2_PSR); /* enable dma */
outb(WIN16K, io + N2_PSR);
outb(WIN32K, io + N2_PSR);
outb(WIN64K, io + N2_PSR);