4 files changed, 27 insertions, 0 deletions

diff --git a/isa/checker.cpp b/isa/checker.cpp
index 05b59a9..1919bd1 100644
--- a/isa/checker.cpp
+++ b/isa/checker.cpp
@@ -28,6 +28,8 @@ void checker::execute() {
         inst.acc = acc;
     if (inst.need_read_link)
         inst.link = link;
+    if (inst.need_read_mq)
+        inst.mq = mq;
     if (inst.read_ctlreg.has_value())
         inst.ctlval = ctlregs[*inst.read_ctlreg];
     inst.execute();
@@ -35,6 +37,8 @@ void checker::execute() {
         acc = inst.acc.value();
     if (inst.need_write_link)
         link = inst.link.value();
+    if (inst.need_write_mq)
+        mq = inst.mq.value();
     if (inst.write_ctlreg.has_value())
         ctlregs[*inst.write_ctlreg] = inst.ctlval.value();
     if (inst.need_exec_store)
diff --git a/isa/checker.h b/isa/checker.h
index 1ea572b..d70997f 100644
--- a/isa/checker.h
+++ b/isa/checker.h
@@ -38,6 +38,7 @@ struct funcmem {
 struct checker {
     unsigned int acc = 0;
     unsigned int link = 0;
+    unsigned int mq = 0;
     unsigned int pc = 00200;
     std::array<unsigned int, NUM_CTLREGS> ctlregs;
     instruction_context inst;
diff --git a/isa/decode.cpp b/isa/decode.cpp
index 1d46375..1979982 100644
--- a/isa/decode.cpp
+++ b/isa/decode.cpp
@@ -155,6 +155,25 @@ instruction_context decode(unsigned int dfifb, unsigned int pc, unsigned int bit
                     if (skip)
                         ctx.next_pc = (ctx.next_pc & 070000) | ((ctx.next_pc + 1) & 007777);
                 };
+            } else if ((bits & 0401) == 0401) {
+                bool cla = bits & 0200;
+                bool mqa = bits & 0100;
+                bool mql = bits & 0020;
+                bool extended_arith = bits & 0056;
+                inst.need_read_acc = mqa || mql;
+                inst.need_read_mq = mqa;
+                inst.need_write_acc = cla || mqa;
+                inst.need_write_mq = mql;
+                inst.ef = [cla, mqa, mql, extended_arith](auto &ctx) {
+                    assert(!extended_arith);
+                    if (cla) ctx.acc = 0;
+                    auto new_acc = ctx.acc;
+                    auto new_mq = ctx.mq;
+                    if (mqa) new_acc = ctx.acc.value() | ctx.mq.value();
+                    if (mql) new_mq = ctx.acc.value();
+                    ctx.acc = new_acc;
+                    ctx.mq = new_mq;
+                };
             } else {
                 assert(false);
             }
diff --git a/isa/isa.h b/isa/isa.h
index 3b8220e..11a8db2 100644
--- a/isa/isa.h
+++ b/isa/isa.h
@@ -22,9 +22,11 @@ struct instruction_context {
     bool need_exec_load = false;        // data = mem[final_address]
     bool need_read_acc = false;         // acc = %acc
     bool need_read_link = false;        // link = %link
+    bool need_read_mq = false;          // mq = %mq
     std::optional<ctlreg> read_ctlreg;  // ctlval = %[read_ctlreg]
     bool need_write_acc = false;        // %acc = acc
     bool need_write_link = false;       // %link = link
+    bool need_write_mq = false;         // %mq = mq
     std::optional<ctlreg> write_ctlreg; // %[write_ctlreg] = ctlval
     bool need_exec_store = false;       // mem[final_address] = data
     bool possibly_redirects = false;    // %pc = next_pc
@@ -40,6 +42,7 @@ struct instruction_context {
     std::optional<unsigned int> data;
     std::optional<unsigned int> acc;
     std::optional<bool> link;
+    std::optional<unsigned int> mq;
     bool halt = false;
 };