diff --git a/pkg/urbit/daemon/main.c b/pkg/urbit/daemon/main.c
index 0c747adeaf..147f30a085 100644
--- a/pkg/urbit/daemon/main.c
+++ b/pkg/urbit/daemon/main.c
@@ -166,6 +166,9 @@ _main_init(void)
   u3_Host.ops_u.puf_c = "jam";
   u3_Host.ops_u.hap_w = 50000;
   u3_Host.ops_u.kno_w = DefaultKernel;
+
+  u3_Host.ops_u.lut_y = u3a_bits + 2;
+  u3_Host.ops_u.lom_y = u3a_bits + 2;
 }
 
 /* _main_pier_run(): get pier from binary path (argv[0]), if appropriate
@@ -218,6 +221,7 @@ _main_getopt(c3_i argc, c3_c** argv)
     { "json-trace",          no_argument,       NULL, 'j' },
     { "kernel-stage",        required_argument, NULL, 'K' },
     { "key-file",            required_argument, NULL, 'k' },
+    { "loom",                required_argument, NULL, c3__loom },
     { "local",               no_argument,       NULL, 'L' },
     { "lite-boot",           no_argument,       NULL, 'l' },
     { "replay-to",           required_argument, NULL, 'n' },
@@ -240,6 +244,9 @@ _main_getopt(c3_i argc, c3_c** argv)
     { "exit",                no_argument,       NULL, 'x' },
     { "scry-into",           required_argument, NULL, 'Y' },
     { "scry-format",         required_argument, NULL, 'Z' },
+    //
+    { "urth-loom",           required_argument, NULL, 5 },
+    //
     { NULL, 0, NULL, 0 },
   };
 
@@ -248,6 +255,17 @@ _main_getopt(c3_i argc, c3_c** argv)
                  lop_u, &lid_i)) )
   {
     switch ( ch_i ) {
+      case 5: {  //  urth-loom
+        c3_w lut_w;
+        c3_o res_o = _main_readw(optarg, u3a_bits + 3, &lut_w);
+        if ( (c3n == res_o) || (lut_w < 20) ) {
+          fprintf(stderr, "error: --urth-loom must be >= 20 and <= %u\r\n", u3a_bits + 2);
+          return c3n;
+        }
+
+        u3_Host.ops_u.lut_y = lut_w;
+        break;
+      }
       case 'X': {
         u3_Host.ops_u.pek_c = strdup(optarg);
         break;
@@ -348,6 +366,16 @@ _main_getopt(c3_i argc, c3_c** argv)
         } else u3_Host.ops_u.pes_s = arg_w;
         break;
       }
+      case c3__loom: {
+        c3_w lom_w;
+        c3_o res_o = _main_readw(optarg, u3a_bits + 3, &lom_w);
+        if ( (c3n == res_o) || (lom_w < 20) ) {
+          fprintf(stderr, "error: --loom must be >= 20 and <= %u\r\n", u3a_bits + 2);
+          return c3n;
+        }
+        u3_Host.ops_u.lom_y = lom_w;
+        break;
+      }
       case c3__noco: {
         u3_Host.ops_u.con = c3n;
         break;
@@ -662,6 +690,7 @@ u3_ve_usage(c3_i argc, c3_c** argv)
     "-K, --kernel-stage STAGE      Start at Hoon kernel version stage\n",
     "-k, --key-file KEYS           Private key file (see also -G)\n",
     "-L, --local                   Local networking only\n",
+    "    --loom                    Set loom to binary exponent (31 == 2GB)\n"
     "-l, --lite-boot               Most-minimal startup\n",
     "-n, --replay-to NUMBER        Replay up to event\n",
     "-P, --profile                 Profiling\n",
@@ -999,9 +1028,9 @@ static void
 _cw_serf_commence(c3_i argc, c3_c* argv[])
 {
 #ifdef U3_OS_mingw
-  if ( 8 > argc ) {
+  if ( 9 > argc ) {
 #else
-  if ( 7 > argc ) {
+  if ( 8 > argc ) {
 #endif
     fprintf(stderr, "serf: missing args\n");
     exit(1);
@@ -1013,9 +1042,11 @@ _cw_serf_commence(c3_i argc, c3_c* argv[])
   c3_c*      key_c = argv[3]; // XX use passkey
   c3_c*      wag_c = argv[4];
   c3_c*      hap_c = argv[5];
-  c3_c*      eve_c = argv[6];
+  c3_c*      lom_c = argv[6];
+  c3_w       lom_w;
+  c3_c*      eve_c = argv[7];
 #ifdef U3_OS_mingw
-  c3_c*      han_c = argv[7];
+  c3_c*      han_c = argv[8];
   _cw_intr_win(han_c);
 #endif
 
@@ -1041,6 +1072,7 @@ _cw_serf_commence(c3_i argc, c3_c* argv[])
   {
     sscanf(wag_c, "%" SCNu32, &u3C.wag_w);
     sscanf(hap_c, "%" SCNu32, &u3_Host.ops_u.hap_w);
+    sscanf(lom_c, "%" SCNu32, &lom_w);
 
     if ( 1 != sscanf(eve_c, "%" PRIu64, &eve_d) ) {
       fprintf(stderr, "serf: rock: invalid number '%s'\r\n", argv[4]);
@@ -1064,7 +1096,7 @@ _cw_serf_commence(c3_i argc, c3_c* argv[])
   //
   {
     u3V.dir_c = strdup(dir_c);
-    u3V.sen_d = u3V.dun_d = u3m_boot(dir_c, u3a_bytes);
+    u3V.sen_d = u3V.dun_d = u3m_boot(dir_c, (size_t)1 << lom_w);
 
     if ( eve_d ) {
       //  XX need not be fatal, need a u3m_reboot equivalent
@@ -1746,8 +1778,10 @@ _cw_utils(c3_i argc, c3_c* argv[])
   //        [?(%vere %fetch-vere) dir=@t]                 ::  download vere
   //        [%vile dir=@t]                                ::  extract keys
   //    ::                                                ::    ipc:
-  //        [%serf dir=@t key=@t wag=@t hap=@ud eve=@ud]  ::  compute
-  //    ==
+  //        $:  %serf                                     ::  compute
+  //            dir=@t  key=@t wag=@t hap=@ud             ::
+  //            lom=@ud eve=@ud                           ::
+  //    ==  ==                                            ::
   //
   //    NB: don't print to anything other than stderr;
   //    other streams may be used for ipc.
@@ -1974,7 +2008,7 @@ main(c3_i   argc,
     //  starting u3m configures OpenSSL memory functions, so we must do it
     //  before any OpenSSL allocations
     //
-    u3m_boot_lite(u3a_bytes);
+    u3m_boot_lite((size_t)1 << u3_Host.ops_u.lut_y);
 
     //  Initialize OpenSSL for client and server
     //
diff --git a/pkg/urbit/include/c/motes.h b/pkg/urbit/include/c/motes.h
index 9945fc5443..f67a50f4ed 100644
--- a/pkg/urbit/include/c/motes.h
+++ b/pkg/urbit/include/c/motes.h
@@ -699,6 +699,7 @@
 #   define c3__lond   c3_s4('l','o','n','d')
 #   define c3__lonk   c3_s4('l','o','n','k')
 #   define c3__look   c3_s4('l','o','o','k')
+#   define c3__loom   c3_s4('l','o','o','m')
 #   define c3__loop   c3_s4('l','o','o','p')
 #   define c3__lorb   c3_s4('l','o','r','b')
 #   define c3__lord   c3_s4('l','o','r','d')
diff --git a/pkg/urbit/include/vere/vere.h b/pkg/urbit/include/vere/vere.h
index d33d1ff84e..d02771343f 100644
--- a/pkg/urbit/include/vere/vere.h
+++ b/pkg/urbit/include/vere/vere.h
@@ -291,6 +291,8 @@
         c3_c*   key_c;                      //  -k, private key file
         c3_o    net;                        //  -L, local-only networking
         c3_o    lit;                        //  -l, lite mode
+        c3_y    lom_y;                      //      loom bex
+        c3_y    lut_y;                      //      urth-loom bex
         c3_c*   til_c;                      //  -n, play till eve_d
         c3_o    pro;                        //  -P, profile
         c3_s    per_s;                      //      http port
diff --git a/pkg/urbit/vere/lord.c b/pkg/urbit/vere/lord.c
index cc7af14f6b..2051908485 100644
--- a/pkg/urbit/vere/lord.c
+++ b/pkg/urbit/vere/lord.c
@@ -1157,11 +1157,12 @@ u3_lord_init(c3_c* pax_c, c3_w wag_w, c3_d key_d[4], u3_lord_cb cb_u)
   //  spawn new process and connect to it
   //
   {
-    c3_c* arg_c[8];
+    c3_c* arg_c[10];
     c3_c  key_c[256];
     c3_c  wag_c[11];
     c3_c  hap_c[11];
     c3_c  cev_c[11];
+    c3_c  lom_c[11];
     c3_i  err_i;
 
     sprintf(key_c, "%" PRIx64 ":%" PRIx64 ":%" PRIx64 ":%" PRIx64 "",
@@ -1174,30 +1175,34 @@ u3_lord_init(c3_c* pax_c, c3_w wag_w, c3_d key_d[4], u3_lord_cb cb_u)
 
     sprintf(hap_c, "%u", u3_Host.ops_u.hap_w);
 
+    sprintf(lom_c, "%u", u3_Host.ops_u.lom_y);
+
     arg_c[0] = god_u->bin_c;            //  executable
     arg_c[1] = "serf";                  //  protocol
     arg_c[2] = god_u->pax_c;            //  path to checkpoint directory
     arg_c[3] = key_c;                   //  disk key
     arg_c[4] = wag_c;                   //  runtime config
     arg_c[5] = hap_c;                   //  hash table size
+    arg_c[6] = lom_c;                   //  loom bex
 
     if ( u3_Host.ops_u.roc_c ) {
       //  XX validate
       //
-      arg_c[6] = u3_Host.ops_u.roc_c;
+      arg_c[7] = u3_Host.ops_u.roc_c;
     }
     else {
-      arg_c[6] = "0";
+      arg_c[7] = "0";
     }
 
 #ifdef U3_OS_mingw
     sprintf(cev_c, "%" PRIu64, u3_Host.cev_u);
-    arg_c[7] = cev_c;
-    arg_c[8] = 0;
+    arg_c[8] = cev_c;
 #else
-    arg_c[7] = 0;
+    arg_c[8] = 0;
 #endif
 
+    arg_c[9] = 0;
+
     uv_pipe_init(u3L, &god_u->inn_u.pyp_u, 0);
     uv_timer_init(u3L, &god_u->out_u.tim_u);
     uv_pipe_init(u3L, &god_u->out_u.pyp_u, 0);