void
count_routing_transistors (int num_switch, float R_minW_nmos,
float R_minW_pmos)
{
int *num_inputs_to_cblock;
int iswitch, i, j, iseg, max_inputs_to_cblock;
float input_cblock_trans;
const float trans_sram_bit = 6.;
float trans_cblock_to_lblock_buf;
input_cblock_trans =
get_cblock_trans (num_inputs_to_cblock, max_inputs_to_cblock,
trans_cblock_to_lblock_buf, trans_sram_bit);
}
void count_routing_transistors (int num_switch, float R_minW_nmos,
float R_minW_pmos) {
/* Counts how many transistors are needed to implement the FPGA routing *
* resources. Call this only when an rr_graph exists. It does not count *
* the transistors used in logic blocks, but it counts the transistors in *
* the input connection block multiplexers and in the output pin drivers and *
* pass transistors. NB: this routine assumes pass transistors always *
* generate two edges (one forward, one backward) between two nodes. *
* Physically, this is what happens -- make sure your rr_graph does it. *
* *
* I assume a minimum width transistor takes 1 unit of area. A double-width *
* transistor takes the twice the diffusion width, but the same spacing, so *
* I assume it takes 1.5x the area of a minimum-width transitor. I always *
* design tri-state buffers as a buffer followed by a pass transistor. *
* I make Rbuffer = Rpass_transitor = 1/2 Rtri-state_buffer. *
* I make the pull-up and pull-down sides of the buffer the same strength -- *
* i.e. I make the p transistor R_minW_pmos / R_minW_nmos wider than the n *
* transistor. *
* *
* I generate two area numbers in this routine: ntrans_sharing and *
* ntrans_no_sharing. ntrans_sharing exactly reflects what the timing *
* analyzer, etc. works with -- each switch is a completely self contained *
* pass transistor or tri-state buffer. In the case of tri-state buffers *
* this is rather pessimisitic. The inverter chain part of the buffer (as *
* opposed to the pass transistor + SRAM output part) can be shared by *
* several switches in the same location. Obviously all the switches from *
* an OPIN can share one buffer. Also, CHANX and CHANY switches at the same *
* spot (i,j) on a single segment can share a buffer. For a more realistic *
* area number I assume all buffered switches from a node that are at the *
* *same (i,j) location* can share one buffer. Only the lowest resistance *
* (largest) buffer is implemented. In practice, you might want to build *
* something that is 1.5x or 2x the largest buffer, so this may be a bit *
* optimistic (but I still think it's pretty reasonable). */
int *num_inputs_to_cblock; /* [0..num_rr_nodes-1], but all entries not */
/* corresponding to IPINs will be 0. */
boolean *cblock_counted; /* [0..max(nx,ny)] -- 0th element unused. */
float *shared_buffer_trans; /* [0..max_nx,ny)] */
float *unsharable_switch_trans, *sharable_switch_trans; /* [0..num_switch-1] */
t_rr_type from_rr_type, to_rr_type;
int from_node, to_node, iedge, num_edges, maxlen;
int iswitch, i, j, iseg, max_inputs_to_cblock;
float input_cblock_trans, shared_opin_buffer_trans;
const float trans_sram_bit = 6.;
/* Two variables below are the accumulator variables that add up all the *
* transistors in the routing. Make doubles so that they don't stop *
* incrementing once adding a switch makes a change of less than 1 part in *
* 10^7 to the total. If this still isn't good enough (adding 1 part in *
* 10^15 will still be thrown away), compute the transistor count in *
* "chunks", by adding up inodes 1 to 1000, 1001 to 2000 and then summing *
* the partial sums together. */
double ntrans_sharing, ntrans_no_sharing;
/* Buffers from the routing to the ipin cblock inputs, and from the ipin *
* cblock outputs to the logic block, respectively. Assume minimum size n *
* transistors, and ptransistors sized to make the pull-up R = pull-down R. */
float trans_track_to_cblock_buf;
float trans_cblock_to_lblock_buf;
ntrans_sharing = 0.;
ntrans_no_sharing = 0.;
max_inputs_to_cblock = 0;
/* Assume the two buffers below are 4x minimum drive strength (enough to *
* drive a fanout of up to 16 pretty nicely -- should cover a reasonable *
* wiring C plus the fanout. */
trans_track_to_cblock_buf = trans_per_buf (R_minW_nmos/4., R_minW_nmos,
R_minW_pmos);
trans_cblock_to_lblock_buf = trans_per_buf (R_minW_nmos/4., R_minW_nmos,
R_minW_pmos);
/* trans_track_to_cblock_buf = 1. + trans_per_R (R_minW_nmos, R_minW_pmos);
trans_cblock_to_lblock_buf = 1. + trans_per_R (R_minW_nmos, R_minW_pmos); */
num_inputs_to_cblock = (int *) my_calloc (num_rr_nodes, sizeof (int));
maxlen = max (nx, ny) + 1;
cblock_counted = (boolean *) my_calloc (maxlen, sizeof (boolean));
shared_buffer_trans = (float *) my_calloc (maxlen, sizeof (float));
unsharable_switch_trans = alloc_and_load_unsharable_switch_trans (num_switch,
trans_sram_bit, R_minW_nmos);
sharable_switch_trans = alloc_and_load_sharable_switch_trans (num_switch,
trans_sram_bit, R_minW_nmos, R_minW_pmos);
for (from_node=0; from_node<num_rr_nodes; from_node++) {
from_rr_type = rr_node[from_node].type;
switch (from_rr_type) {
case CHANX:
case CHANY:
num_edges = rr_node[from_node].num_edges;
for (iedge=0; iedge<num_edges; iedge++) {
to_node = rr_node[from_node].edges[iedge];
to_rr_type = rr_node[to_node].type;
switch (to_rr_type) {
case CHANX:
case CHANY:
iswitch = rr_node[from_node].switches[iedge];
if (switch_inf[iswitch].buffered) {
iseg = seg_index_of_sblock (from_node, to_node);
shared_buffer_trans[iseg] = max (shared_buffer_trans[iseg],
sharable_switch_trans[iswitch]);
ntrans_no_sharing += unsharable_switch_trans[iswitch] +
sharable_switch_trans[iswitch];
ntrans_sharing += unsharable_switch_trans[iswitch];
}
else if (from_node < to_node) {
/* Pass transistor shared by two edges -- only count once. *
* Also, no part of a pass transistor is sharable. */
ntrans_no_sharing += unsharable_switch_trans[iswitch];
ntrans_sharing += unsharable_switch_trans[iswitch];
}
break;
case IPIN:
num_inputs_to_cblock[to_node]++;
max_inputs_to_cblock = max (max_inputs_to_cblock,
num_inputs_to_cblock[to_node]);
iseg = seg_index_of_cblock (from_rr_type, to_node);
if (cblock_counted[iseg] == FALSE) {
cblock_counted[iseg] = TRUE;
ntrans_sharing += trans_track_to_cblock_buf;
ntrans_no_sharing += trans_track_to_cblock_buf;
}
break;
default:
printf ("Error in count_routing_transistors: Unexpected \n"
"connection from node %d (type %d) to node %d (type %d).\n",
from_node, from_rr_type, to_node, to_rr_type);
exit (1);
break;
} /* End switch on to_rr_type. */
} /* End for each edge. */
/* Now add in the shared buffer transistors, and reset some flags. */
if (from_rr_type == CHANX) {
for (i=rr_node[from_node].xlow-1; i<=rr_node[from_node].xhigh; i++) {
ntrans_sharing += shared_buffer_trans[i];
shared_buffer_trans[i] = 0.;
}
for (i=rr_node[from_node].xlow; i<=rr_node[from_node].xhigh; i++)
cblock_counted[i] = FALSE;
}
else { /* CHANY */
for (j=rr_node[from_node].ylow-1; j<=rr_node[from_node].yhigh; j++) {
ntrans_sharing += shared_buffer_trans[j];
shared_buffer_trans[j] = 0.;
}
for (j=rr_node[from_node].ylow; j<=rr_node[from_node].yhigh; j++)
cblock_counted[j] = FALSE;
}
break;
case OPIN:
num_edges = rr_node[from_node].num_edges;
shared_opin_buffer_trans = 0.;
for (iedge=0; iedge<num_edges; iedge++) {
iswitch = rr_node[from_node].switches[iedge];
ntrans_no_sharing += unsharable_switch_trans[iswitch] +
sharable_switch_trans[iswitch];
ntrans_sharing += unsharable_switch_trans[iswitch];
shared_opin_buffer_trans = max (shared_opin_buffer_trans,
sharable_switch_trans[iswitch]);
}
ntrans_sharing += shared_opin_buffer_trans;
break;
default:
break;
} /* End switch on from_rr_type */
} /* End for all nodes */
free (cblock_counted);
free (shared_buffer_trans);
free (unsharable_switch_trans);
free (sharable_switch_trans);
/* Now add in the input connection block transistors. */
input_cblock_trans = get_cblock_trans (num_inputs_to_cblock,
max_inputs_to_cblock, trans_cblock_to_lblock_buf, trans_sram_bit);
free (num_inputs_to_cblock);
ntrans_sharing += input_cblock_trans;
ntrans_no_sharing += input_cblock_trans;
printf ("\nRouting area (in minimum width transistor areas):\n");
printf ("Assuming no buffer sharing (pessimistic). Total: %#g Per clb: "
"%#g\n", ntrans_no_sharing, ntrans_no_sharing / (float) (nx * ny));
printf ("Assuming buffer sharing (slightly optimistic). Total: %#g Per clb: "
"%#g\n\n", ntrans_sharing, ntrans_sharing / (float) (nx * ny));
}
