diff --git a/README.md b/README.md
index 5d1a944..7477a70 100644
--- a/README.md
+++ b/README.md
@@ -39,6 +39,8 @@ it's not a z80 emulator, but a *javascript port of Collapse OS*!
 
 * `blk`: Collapse OS filesystem's content. That's actually where Collapse OS'
          source code is located. Everything else is peripheral.
+* `cvm`: A C implementation of Collapse OS, allowing it to run natively on any
+         POSIX platform.
 * `recipes`: collection of recipes that assemble Collapse OS on a specific
              machine.
 * `tools`: Tools for working with Collapse OS from "modern" environments. For
diff --git a/cvm/Makefile b/cvm/Makefile
new file mode 100644
index 0000000..6b29eaa
--- /dev/null
+++ b/cvm/Makefile
@@ -0,0 +1,43 @@
+TARGETS = forth
+OBJS = vm.o
+BLKPACK = ../tools/blkpack
+BLKUNPACK = ../tools/blkunpack
+
+.PHONY: all
+all: $(TARGETS)
+
+$(BLKPACK):
+	$(MAKE) -C ../tools
+
+.PHONY: $(BLKUNPACK)
+$(BLKUNPACK): $(BLKPACK)
+
+stage: stage.c $(OBJS) blkfs
+	$(CC) stage.c $(OBJS) -o $@
+
+blkfs: $(BLKPACK)
+	$(BLKPACK) ../blk > $@
+
+forth: forth.c $(OBJS) blkfs
+	$(CC) forth.c $(OBJS) -lncurses -o $@
+
+vm.o: vm.c
+	$(CC) -DFBIN_PATH=\"`pwd`/forth.bin\" -DBLKFS_PATH=\"`pwd`/blkfs\" -c -o vm.o vm.c
+
+
+.PHONY: updatebootstrap
+updatebootstrap: stage xcomp.fs pack
+	./stage < xcomp.fs > new.bin
+	mv new.bin forth.bin
+
+.PHONY: pack
+pack:
+	rm blkfs && $(MAKE) blkfs
+
+.PHONY: unpack
+unpack:
+	$(BLKUNPACK) ../blk < blkfs
+
+.PHONY: clean
+clean:
+	rm -f $(TARGETS) *.o blkfs
diff --git a/cvm/forth.c b/cvm/forth.c
new file mode 100644
index 0000000..64e84e2
--- /dev/null
+++ b/cvm/forth.c
@@ -0,0 +1,119 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <curses.h>
+#include <termios.h>
+#include "vm.h"
+
+#define WCOLS 80
+#define WLINES 32
+#define STDIO_PORT 0x00
+// This binary is also used for automated tests and those tests, when
+// failing, send a non-zero value to RET_PORT to indicate failure
+#define RET_PORT 0x01
+#define SETX_PORT 0x05
+#define SETY_PORT 0x06
+
+static FILE *fp;
+static int retcode = 0;
+WINDOW *bw, *dw, *w;
+
+void debug_panel()
+{
+    char buf[30];
+    VM_debugstr(buf);
+    mvwaddnstr(dw, 0, 0, buf, 30);
+    wrefresh(dw);
+}
+
+static uint8_t iord_stdio()
+{
+    int c;
+    if (fp != NULL) {
+        c = getc(fp);
+    } else {
+        debug_panel();
+        c = wgetch(w);
+    }
+    if (c == EOF) {
+        c = 4; // ASCII EOT
+    }
+    return (uint8_t)c;
+}
+
+static void iowr_stdio(uint8_t val)
+{
+    if (fp != NULL) {
+        putchar(val);
+    } else {
+        if (val >= 0x20 || val == '\n') {
+            wechochar(w, val);
+        } else if (val == 0x08) {
+            int y, x; getyx(w, y, x);
+            wmove(w, y, x-1);
+        }
+    }
+}
+
+static void iowr_ret(uint8_t val)
+{
+    retcode = val;
+}
+
+static void iowr_setx(uint8_t val)
+{
+    int y, x; getyx(w, y, x);
+    wmove(w, y, val);
+}
+
+static void iowr_sety(uint8_t val)
+{
+    int y, x; getyx(w, y, x);
+    wmove(w, val, x);
+}
+
+int main(int argc, char *argv[])
+{
+    VM *vm = VM_init();
+    if (!vm) {
+        return 1;
+    }
+    vm->iord[STDIO_PORT] = iord_stdio;
+    vm->iowr[STDIO_PORT] = iowr_stdio;
+    vm->iowr[RET_PORT] = iowr_ret;
+    vm->iowr[SETX_PORT] = iowr_setx;
+    vm->iowr[SETY_PORT] = iowr_sety;
+    w = NULL;
+    if (argc == 2) {
+        fp = fopen(argv[1], "r");
+        if (fp == NULL) {
+            fprintf(stderr, "Can't open %s\n", argv[1]);
+            return 1;
+        }
+        while (VM_steps(1000));
+        fclose(fp);
+    } else if (argc == 1) {
+        fp = NULL;
+        initscr(); cbreak(); noecho(); nl(); clear();
+        // border window
+        bw = newwin(WLINES+2, WCOLS+2, 0, 0);
+        wborder(bw, 0, 0, 0, 0, 0, 0, 0, 0);
+        wrefresh(bw);
+        // debug panel
+        dw = newwin(1, 30, LINES-1, COLS-30);
+        w = newwin(WLINES, WCOLS, 1, 1);
+        scrollok(w, 1);
+        while (VM_steps(1000)) {
+            debug_panel();
+        }
+        nocbreak(); echo(); delwin(w); delwin(bw); delwin(dw); endwin();
+        printf("\nDone!\n");
+        fprintf(stderr, "Done!\n");
+        VM_printdbg();
+    } else {
+        fprintf(stderr, "Usage: ./forth [filename]\n");
+        retcode = 1;
+    }
+    VM_deinit();
+    return 0;
+}
diff --git a/cvm/vm.c b/cvm/vm.c
new file mode 100644
index 0000000..b6b6188
--- /dev/null
+++ b/cvm/vm.c
@@ -0,0 +1,392 @@
+#include <stdio.h>
+#include <string.h>
+#include "vm.h"
+
+// Port for block reads. Each read or write has to be done in 5 IO writes:
+// 1 - r/w. 1 for read, 2 for write.
+// 2 - blkid MSB
+// 3 - blkid LSB
+// 4 - dest addr MSB
+// 5 - dest addr LSB
+#define BLK_PORT 0x03
+
+#ifndef BLKFS_PATH
+#error BLKFS_PATH needed
+#endif
+#ifndef FBIN_PATH
+#error FBIN_PATH needed
+#endif
+
+static VM vm;
+static uint64_t blkop = 0; // 5 bytes
+static FILE *blkfp;
+
+static byte io_read(word addr)
+{
+    addr &= 0xff;
+    IORD fn = vm.iord[addr];
+    if (fn != NULL) {
+        return fn();
+    } else {
+        fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
+        return 0;
+    }
+}
+
+static void io_write(word addr, byte val)
+{
+    addr &= 0xff;
+    IOWR fn = vm.iowr[addr];
+    if (fn != NULL) {
+        fn(val);
+    } else {
+        fprintf(stderr, "Out of bounds I/O write: %d / %d (0x%x)\n", addr, val, val);
+    }
+}
+
+static void iowr_blk(byte val)
+{
+    blkop <<= 8;
+    blkop |= val;
+    byte rw = blkop >> 32;
+    if (rw) {
+        word blkid = (blkop >> 16);
+        word dest = blkop & 0xffff;
+        blkop = 0;
+        fseek(blkfp, blkid*1024, SEEK_SET);
+        if (rw==2) { // write
+            fwrite(&vm.mem[dest], 1024, 1, blkfp);
+        } else { // read
+            fread(&vm.mem[dest], 1024, 1, blkfp);
+        }
+    }
+}
+
+static word gw(word addr) { return vm.mem[addr+1] << 8 | vm.mem[addr]; }
+static void sw(word addr, word val) {
+    vm.mem[addr] = val;
+    vm.mem[addr+1] = val >> 8;
+}
+static word pop() { return vm.mem[vm.SP++] | vm.mem[vm.SP++] << 8; }
+static void push(word x) {
+    vm.SP -= 2; sw(vm.SP, x);
+    if (vm.SP < vm.minSP) { vm.minSP = vm.SP; }
+}
+static word popRS() { word x = gw(vm.RS); vm.RS -= 2; return x; }
+static void pushRS(word val) {
+    vm.RS += 2; sw(vm.RS, val);
+    if (vm.RS > vm.maxRS) { vm.maxRS = vm.RS; }
+}
+static void execute(word wordref) {
+    byte wtype = vm.mem[wordref];
+    if (wtype == 0) { // native
+        vm.nativew[vm.mem[wordref+1]]();
+    } else if (wtype == 1) { // compiled
+        pushRS(vm.IP);
+        vm.IP = wordref+1;
+    } else { // cell or does
+        push(wordref+1);
+        if (wtype == 4) {
+            vm.IP = gw(wordref+3);
+        }
+    }
+}
+static word find(word daddr, word waddr) {
+    byte len = vm.mem[waddr];
+    while (1) {
+        if ((vm.mem[daddr-1] & 0x7f) == len) {
+            if (strncmp(&vm.mem[waddr+1], &vm.mem[daddr-3-len], len) == 0) {
+                return daddr;
+            }
+        }
+        daddr -= 3;
+        word offset = gw(daddr);
+        if (offset) {
+            daddr -= offset;
+        } else {
+            return 0;
+        }
+    }
+}
+
+static void EXIT() { vm.IP = popRS(); }
+static void _br_() { vm.IP += gw(vm.IP); };
+static void _cbr_() { if (!pop()) { _br_(); } else { vm.IP += 2; } };
+static void _loop_() {
+    word I = gw(vm.RS); I++; sw(vm.RS, I);
+    if (I == gw(vm.RS-2)) { // don't branch
+        popRS(); popRS();
+        vm.IP += 2;
+    } else { // branch
+        _br_();
+    }
+}
+static void SP_to_R_2() { word x = pop(); pushRS(pop()); pushRS(x); }
+static void nlit() { push(gw(vm.IP)); vm.IP += 2; }
+static void slit() { push(vm.IP); vm.IP += vm.mem[vm.IP] + 1; }
+static void SP_to_R() { pushRS(pop()); }
+static void R_to_SP() { push(popRS()); }
+static void R_to_SP_2() { word x = popRS(); push(popRS()); push(x); }
+static void EXECUTE() { execute(pop()); }
+static void ROT() { // a b c -- b c a
+    word c = pop(); word b = pop(); word a = pop();
+    push(b); push(c); push(a);
+}
+static void DUP() { // a -- a a
+    word a = pop(); push(a); push(a);
+}
+static void CDUP() {
+    word a = pop(); push(a); if (a) { push(a); }
+}
+static void DROP() { pop(); }
+static void SWAP() { // a b -- b a
+    word b = pop(); word a = pop();
+    push(b); push(a);
+}
+static void OVER() { // a b -- a b a
+    word b = pop(); word a = pop();
+    push(a); push(b); push(a);
+}
+static void PICK() {
+    word x = pop();
+    push(gw(vm.SP+x*2));
+}
+static void _roll_() { //   "1 2 3 4 4 (roll)" --> "1 3 4 4"
+    word x = pop();
+    while (x) { vm.mem[vm.SP+x+2] = vm.mem[vm.SP+x]; x--; }
+}
+static void DROP2() { pop(); pop(); }
+static void DUP2() { // a b -- a b a b
+    word b = pop(); word a = pop();
+    push(a); push(b); push(a); push(b);
+}
+static void S0() { push(SP_ADDR); }
+static void Saddr() { push(vm.SP); }
+static void AND() { push(pop() & pop()); }
+static void OR() { push(pop() | pop()); }
+static void XOR() { push(pop() ^ pop()); }
+static void NOT() { push(!pop()); }
+static void PLUS() { push(pop() + pop()); }
+static void MINUS() {
+    word b = pop(); word a = pop();
+    push(a - b);
+}
+static void MULT() { push(pop() * pop()); }
+static void DIVMOD() {
+    word b = pop(); word a = pop();
+    push(a % b); push(a / b);
+}
+static void STORE() {
+    word a = pop(); word val = pop();
+    sw(a, val);
+}
+static void FETCH() { push(gw(pop())); }
+static void CSTORE() {
+    word a = pop(); word val = pop();
+    vm.mem[a] = val;
+}
+static void CFETCH() { push(vm.mem[pop()]); }
+static void IO_OUT() {
+    word a = pop(); word val = pop();
+    io_write(a, val);
+}
+static void IO_IN() { push(io_read(pop())); }
+static void RI() { push(gw(vm.RS)); }
+static void RI_() { push(gw(vm.RS-2)); }
+static void RJ() { push(gw(vm.RS-4)); }
+static void BYE() { vm.running = false; }
+static void _resSP_() { vm.SP = SP_ADDR; }
+static void _resRS_() { vm.RS = RS_ADDR; }
+static void Seq() {
+    word s1 = pop(); word s2 = pop();
+    byte len = vm.mem[s1];
+    if (len == vm.mem[s2]) {
+        s1++; s2++;
+        push(strncmp(&vm.mem[s1], &vm.mem[s2], len) == 0);
+    } else {
+        push(0);
+    }
+}
+static void CMP() {
+    word b = pop(); word a = pop();
+    if (a == b) { push(0); } else if (a > b) { push(1); } else { push(-1); }
+}
+static void _find() {
+    word waddr = pop(); word daddr = pop();
+    daddr = find(daddr, waddr);
+    if (daddr) {
+        push(daddr); push(1);
+    } else {
+        push(waddr); push(0);
+    }
+}
+static void ZERO() { push(0); }
+static void ONE() { push(1); }
+static void MONE() { push(-1); }
+static void PLUS1() { push(pop()+1); }
+static void MINUS1() { push(pop()-1); }
+static void MINUS2() { push(pop()-2); }
+static void PLUS2() { push(pop()+2); }
+static void RSHIFT() { word u = pop(); push(pop()>>u); }
+static void LSHIFT() { word u = pop(); push(pop()<<u); }
+// create a native word with a specific target offset. target is addr of
+// wordref.
+static void create_native_t(word target, char *name, NativeWord func) {
+    int len = strlen(name);
+    strcpy(&vm.mem[target-len-3], name);
+    word prev_off = target - 3 - vm.xcurrent;
+    sw(target-3, prev_off);
+    vm.mem[target-1] = len;
+    vm.mem[target] = 0; // native word type
+    vm.mem[target+1] = vm.nativew_count;
+    vm.nativew[vm.nativew_count++] = func;
+    vm.xcurrent = target;
+}
+
+/* INITIAL BOOTSTRAP PLAN
+
+For the initial bootstrap of the C VM, we treat every native word as a stable
+word, giving it exactly the same memory offset as we have in the z80 forth.bin.
+This will greatly simplify the initial bootstrap because we'll be able to
+directly plug the "core words" part of forth.bin into our C VM and run it.
+Once we have that, we can de-stabilize the native words that aren't part of the
+stable ABI and bootstrap ourselves from ourselves. Good plan, right?
+*/
+VM* VM_init() {
+    fprintf(stderr, "Using blkfs %s\n", BLKFS_PATH);
+    blkfp = fopen(BLKFS_PATH, "r+");
+    if (!blkfp) {
+        fprintf(stderr, "Can't open\n");
+        return NULL;
+    }
+    fseek(blkfp, 0, SEEK_END);
+    if (ftell(blkfp) < 100 * 1024) {
+        fclose(blkfp);
+        fprintf(stderr, "emul/blkfs too small, something's wrong, aborting.\n");
+        return NULL;
+    }
+    fseek(blkfp, 0, SEEK_SET);
+    // initialize memory
+    memset(vm.mem, 0, 0x10000);
+    FILE *bfp = fopen(FBIN_PATH, "r");
+    if (!bfp) {
+        fprintf(stderr, "Can't open forth.bin\n");
+        return NULL;
+    }
+    int i = 0;
+    int c = getc(bfp);
+    while (c != EOF) {
+        vm.mem[i++] = c;
+        c = getc(bfp);
+    }
+    fclose(bfp);
+    vm.SP = SP_ADDR;
+    vm.RS = RS_ADDR;
+    vm.minSP = SP_ADDR;
+    vm.maxRS = RS_ADDR;
+    vm.nativew_count = 0;
+    for (int i=0; i<0x100; i++) {
+        vm.iord[i] = NULL;
+        vm.iowr[i] = NULL;
+    }
+    vm.iowr[BLK_PORT] = iowr_blk;
+    vm.xcurrent = 0x3f; // make EXIT's prev field 0
+    create_native_t(0x42, "EXIT", EXIT);
+    create_native_t(0x53, "(br)", _br_);
+    create_native_t(0x67, "(?br)", _cbr_);
+    create_native_t(0x80, "(loop)", _loop_);
+    create_native_t(0xa9, "2>R", SP_to_R_2);
+    create_native_t(0xbf, "(n)", nlit);
+    create_native_t(0xd4, "(s)", slit);
+    // End of stable ABI
+    create_native_t(0xe7, ">R", SP_to_R);
+    create_native_t(0xf4, "R>", R_to_SP);
+    create_native_t(0x102, "2R>", R_to_SP_2);
+    create_native_t(0x1d4, "EXECUTE", EXECUTE);
+    create_native_t(0x1e1, "ROT", ROT);
+    create_native_t(0x1f4, "DUP", DUP);
+    create_native_t(0x205, "?DUP", CDUP);
+    create_native_t(0x21a, "DROP", DROP);
+    create_native_t(0x226, "SWAP", SWAP);
+    create_native_t(0x238, "OVER", OVER);
+    create_native_t(0x24b, "PICK", PICK);
+    create_native_t(0x26c, "(roll)", _roll_);
+    create_native_t(0x283, "2DROP", DROP2);
+    create_native_t(0x290, "2DUP", DUP2);
+    create_native_t(0x2a2, "S0", S0);
+    create_native_t(0x2af, "'S", Saddr);
+    create_native_t(0x2be, "AND", AND);
+    create_native_t(0x2d3, "OR", OR);
+    create_native_t(0x2e9, "XOR", XOR);
+    create_native_t(0x2ff, "NOT", NOT);
+    create_native_t(0x314, "+", PLUS);
+    create_native_t(0x323, "-", MINUS);
+    create_native_t(0x334, "*", MULT);
+    create_native_t(0x358, "/MOD", DIVMOD);
+    create_native_t(0x37c, "!", STORE);
+    create_native_t(0x389, "@", FETCH);
+    create_native_t(0x39a, "C!", CSTORE);
+    create_native_t(0x3a6, "C@", CFETCH);
+    create_native_t(0x3b8, "PC!", IO_OUT);
+    create_native_t(0x3c6, "PC@", IO_IN);
+    create_native_t(0x3d7, "I", RI);
+    create_native_t(0x3e7, "I'", RI_);
+    create_native_t(0x3f6, "J", RJ);
+    create_native_t(0x407, "BYE", BYE);
+    create_native_t(0x416, "(resSP)", _resSP_);
+    create_native_t(0x427, "(resRS)", _resRS_);
+    create_native_t(0x434, "S=", Seq);
+    create_native_t(0x457, "CMP", CMP);
+    create_native_t(0x476, "_find", _find);
+    create_native_t(0x4a4, "0", ZERO);
+    create_native_t(0x4b0, "1", ONE);
+    create_native_t(0x4bd, "-1", MONE);
+    create_native_t(0x4ca, "1+", PLUS1);
+    create_native_t(0x4d9, "1-", MINUS1);
+    create_native_t(0x4e8, "2+", PLUS2);
+    create_native_t(0x4f8, "2-", MINUS2);
+    create_native_t(0x50c, "RSHIFT", RSHIFT);
+    create_native_t(0x52a, "LSHIFT", LSHIFT);
+    vm.IP = gw(0x04) + 1; // BOOT
+    sw(SYSVARS+0x02, gw(0x08)); // CURRENT
+    sw(SYSVARS+0x04, gw(0x08)); // HERE
+    vm.running = true;
+    return &vm;
+}
+
+void VM_deinit()
+{
+    fclose(blkfp);
+}
+
+bool VM_steps(int n) {
+    if (!vm.running) {
+        fprintf(stderr, "machine halted!\n");
+        return false;
+    }
+    while (n && vm.running) {
+        word wordref = gw(vm.IP);
+        vm.IP += 2;
+        execute(wordref);
+        n--;
+    }
+    return vm.running;
+}
+
+void VM_memdump() {
+    fprintf(stderr, "Dumping memory to memdump. IP %04x\n", vm.IP);
+    FILE *fp = fopen("memdump", "w");
+    fwrite(vm.mem, 0x10000, 1, fp);
+    fclose(fp);
+}
+
+void VM_debugstr(char *s) {
+    sprintf(s, "SP %04x (%04x) RS %04x (%04x)",
+        vm.SP, vm.minSP, vm.RS, vm.maxRS);
+}
+
+void VM_printdbg() {
+    char buf[0x100];
+    VM_debugstr(buf);
+    fprintf(stderr, "%s\n", buf);
+}
diff --git a/cvm/vm.h b/cvm/vm.h
new file mode 100644
index 0000000..5d80abc
--- /dev/null
+++ b/cvm/vm.h
@@ -0,0 +1,46 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+#define SP_ADDR 0xffff
+#define RS_ADDR 0xff00
+#define SYSVARS 0xe800
+
+typedef uint8_t byte;
+typedef uint16_t word;
+// Native words in this C Forth VMs are indexed in an array. The word in memory
+// is the typical 0x00 to indicate native, followed by an index byte. The
+// Execute routine will then know which native word to execute.
+typedef void (*NativeWord) ();
+typedef byte (*IORD) ();
+typedef void (*IOWR) (byte data);
+
+/* Native word placement
+    Being a C VM, all actual native code is outside the VM's memory. However,
+    we have a stable ABI to conform to. VM_init() configures the memory by
+    placing references to stable words at proper offsets, and then add all other
+    native words next to it. This will result in a "boot binary" that is much
+    more compact than a real Collapse OS memory layout.
+*/
+typedef struct {
+    byte mem[0x10000];
+    word SP;
+    word RS;
+    word IP;
+    NativeWord nativew[0x100];
+    byte nativew_count;
+    // Array of 0x100 function pointers to IO read and write routines. Leave to
+    // NULL when IO port is unhandled.
+    IORD iord[0x100];
+    IOWR iowr[0x100];
+    word xcurrent; // only used during native bootstrap
+    word maxRS;
+    word minSP;
+    bool running;
+} VM;
+
+VM* VM_init();
+void VM_deinit();
+bool VM_steps(int n);
+void VM_memdump();
+void VM_debugstr(char *s);
+void VM_printdbg();