xref: /gem5/ext/mcpat/cacti/crossbar.cc

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#include "crossbar.h"

#define ASPECT_THRESHOLD .8
#define ADJ 1

Crossbar::Crossbar(
    double n_inp_,
    double n_out_,
    double flit_size_,
    TechnologyParameter::DeviceType *dt
    ):n_inp(n_inp_), n_out(n_out_), flit_size(flit_size_), deviceType(dt)
{
  min_w_pmos = deviceType->n_to_p_eff_curr_drv_ratio*g_tp.min_w_nmos_;
  Vdd = dt->Vdd;
  CB_ADJ = 1;
}

Crossbar::~Crossbar(){}

double Crossbar::output_buffer()
{

  //Wire winit(4, 4);
  double l_eff = n_inp*flit_size*g_tp.wire_outside_mat.pitch;
  Wire w1(g_ip->wt, l_eff);
  //double s1 = w1.repeater_size *l_eff*ADJ/w1.repeater_spacing;
  double s1 = w1.repeater_size * (l_eff <w1.repeater_spacing?  l_eff *ADJ/w1.repeater_spacing : ADJ);
  double pton_size = deviceType->n_to_p_eff_curr_drv_ratio;
  // the model assumes input capacitance of the wire driver = input capacitance of nand + nor = input cap of the driver transistor
  TriS1 = s1*(1 + pton_size)/(2 + pton_size + 1 + 2*pton_size);
  TriS2 = s1; //driver transistor

  if (TriS1 < 1)
    TriS1 = 1;

  double input_cap = gate_C(TriS1*(2*min_w_pmos + g_tp.min_w_nmos_), 0) +
    gate_C(TriS1*(min_w_pmos + 2*g_tp.min_w_nmos_), 0);
//  input_cap += drain_C_(TriS1*g_tp.min_w_nmos_, NCH, 1, 1, g_tp.cell_h_def) +
//    drain_C_(TriS1*min_w_pmos, PCH, 1, 1, g_tp.cell_h_def)*2 +
//    gate_C(TriS2*g_tp.min_w_nmos_, 0)+
//    drain_C_(TriS1*min_w_pmos, NCH, 1, 1, g_tp.cell_h_def)*2 +
//    drain_C_(TriS1*min_w_pmos, PCH, 1, 1, g_tp.cell_h_def) +
//    gate_C(TriS2*min_w_pmos, 0);
  tri_int_cap = drain_C_(TriS1*g_tp.min_w_nmos_, NCH, 1, 1, g_tp.cell_h_def) +
    drain_C_(TriS1*min_w_pmos, PCH, 1, 1, g_tp.cell_h_def)*2 +
    gate_C(TriS2*g_tp.min_w_nmos_, 0)+
    drain_C_(TriS1*min_w_pmos, NCH, 1, 1, g_tp.cell_h_def)*2 +
    drain_C_(TriS1*min_w_pmos, PCH, 1, 1, g_tp.cell_h_def) +
    gate_C(TriS2*min_w_pmos, 0);
  double output_cap = drain_C_(TriS2*g_tp.min_w_nmos_, NCH, 1, 1, g_tp.cell_h_def) +
    drain_C_(TriS2*min_w_pmos, PCH, 1, 1, g_tp.cell_h_def);
  double ctr_cap = gate_C(TriS2 *(min_w_pmos + g_tp.min_w_nmos_), 0);

  tri_inp_cap = input_cap;
  tri_out_cap = output_cap;
  tri_ctr_cap = ctr_cap;
  return input_cap + output_cap + ctr_cap;
}

void Crossbar::compute_power()
{

  Wire winit(4, 4);
  double tri_cap = output_buffer();
  assert(tri_cap > 0);
  //area of a tristate logic
  double g_area = compute_gate_area(INV, 1, TriS2*g_tp.min_w_nmos_, TriS2*min_w_pmos, g_tp.cell_h_def);
  g_area *= 2; // to model area of output transistors
  g_area += compute_gate_area (NAND, 2, TriS1*2*g_tp.min_w_nmos_, TriS1*min_w_pmos, g_tp.cell_h_def);
  g_area += compute_gate_area (NOR, 2, TriS1*g_tp.min_w_nmos_, TriS1*2*min_w_pmos, g_tp.cell_h_def);
  double width /*per tristate*/ = g_area/(CB_ADJ * g_tp.cell_h_def);
  // effective no. of tristate buffers that need to be laid side by side
  int ntri = (int)ceil(g_tp.cell_h_def/(g_tp.wire_outside_mat.pitch));
  double wire_len = MAX(width*ntri*n_out, flit_size*g_tp.wire_outside_mat.pitch*n_out);
  Wire w1(g_ip->wt, wire_len);

  area.w = wire_len;
  area.h = g_tp.wire_outside_mat.pitch*n_inp*flit_size * CB_ADJ;
  Wire w2(g_ip->wt, area.h);

  double aspect_ratio_cb = (area.h/area.w)*(n_out/n_inp);
  if (aspect_ratio_cb > 1) aspect_ratio_cb = 1/aspect_ratio_cb;

  if (aspect_ratio_cb < ASPECT_THRESHOLD) {
    if (n_out > 2 && n_inp > 2) {
      CB_ADJ+=0.2;
      //cout << "CB ADJ " << CB_ADJ << endl;
      if (CB_ADJ < 4) {
        this->compute_power();
      }
    }
  }



  power.readOp.dynamic = (w1.power.readOp.dynamic + w2.power.readOp.dynamic + (tri_inp_cap * n_out + tri_out_cap * n_inp + tri_ctr_cap + tri_int_cap) * Vdd*Vdd)*flit_size;
  power.readOp.leakage      =  n_inp * n_out * flit_size * (
    cmos_Isub_leakage(g_tp.min_w_nmos_*TriS2*2, min_w_pmos*TriS2*2, 1, inv) *Vdd+
        cmos_Isub_leakage(g_tp.min_w_nmos_*TriS1*3, min_w_pmos*TriS1*3, 2, nand)*Vdd+
        cmos_Isub_leakage(g_tp.min_w_nmos_*TriS1*3, min_w_pmos*TriS1*3, 2, nor) *Vdd+
    w1.power.readOp.leakage + w2.power.readOp.leakage);
  power.readOp.gate_leakage = n_inp * n_out * flit_size * (
          cmos_Ig_leakage(g_tp.min_w_nmos_*TriS2*2, min_w_pmos*TriS2*2, 1, inv) *Vdd+
          cmos_Ig_leakage(g_tp.min_w_nmos_*TriS1*3, min_w_pmos*TriS1*3, 2, nand)*Vdd+
          cmos_Ig_leakage(g_tp.min_w_nmos_*TriS1*3, min_w_pmos*TriS1*3, 2, nor) *Vdd+
          w1.power.readOp.gate_leakage + w2.power.readOp.gate_leakage);

  // delay calculation
  double l_eff = n_inp*flit_size*g_tp.wire_outside_mat.pitch;
  Wire wdriver(g_ip->wt, l_eff);
  double res = g_tp.wire_outside_mat.R_per_um * (area.w+area.h) + tr_R_on(g_tp.min_w_nmos_*wdriver.repeater_size, NCH, 1);
  double cap = g_tp.wire_outside_mat.C_per_um * (area.w + area.h) + n_out*tri_inp_cap + n_inp*tri_out_cap;
  delay = horowitz(w1.signal_rise_time(), res*cap, deviceType->Vth/deviceType->Vdd, deviceType->Vth/deviceType->Vdd, RISE);

  Wire wreset();
}

void Crossbar::print_crossbar()
{
  cout << "\nCrossbar Stats (" << n_inp << "x" << n_out << ")\n\n";
  cout << "Flit size        : " << flit_size << " bits" << endl;
  cout << "Width            : " << area.w << " u" << endl;
  cout << "Height           : " << area.h << " u" << endl;
  cout << "Dynamic Power    : " << power.readOp.dynamic*1e9 * MIN(n_inp, n_out) << " (nJ)" << endl;
  cout << "Leakage Power    : " << power.readOp.leakage*1e3 << " (mW)" << endl;
  cout << "Gate Leakage Power    : " << power.readOp.gate_leakage*1e3 << " (mW)" << endl;
  cout << "Crossbar Delay   : " << delay*1e12 << " ps\n";
}