CL_SEQR1F
vga_wseq(cinfo->regbase, CL_SEQR1F,
long mclk = vga_rseq(cinfo->regbase, CL_SEQR1F) & 0x3f;
old1f = vga_rseq(cinfo->regbase, CL_SEQR1F) & ~0x40;
vga_wseq(cinfo->regbase, CL_SEQR1F, old1f);