if ((clockticks6502 - dmc.lasttick) >= (dmc.period >> 3)) {
        if (dmc.enabled) {
            if (dmc.sampleempty) {
                dmc.sampleempty = 0;
                dmc.bufferbit = 0;
                dmc.samplebuffer = readPPU(dmc.address++);
                if (dmc.address < 0x8000) dmc.address = 0x8000;
                dmc.bytesremain--;
                if (dmc.bytesremain == 0) {
                    if (!dmc.loopmode) {
                        dmc.enabled = 0;
                    } else {
                        dmc.address = (dmc.addressreg << 6) | 0xC000;
                        dmc.bytesremain = (dmc.lengthreg << 4) + 1;
                    }
                }
            }

            if (!dmc.sampleempty) {
                if ((dmc.samplebuffer >> (dmc.bufferbit & 7)) & 1) {
                    if (channels[4] <= 0x7D) channels[4] += 2;
                } else {
                    if (channels[4] >= 2) channels[4] -= 2;
                }
                if (++dmc.bufferbit == 8) {
                    dmc.sampleempty = 1;
                }
            }
        } else channels[4] = 0;

        dmc.lasttick = clockticks6502 - ((clockticks6502 - dmc.lasttick) - (dmc.period >> 3));
    }