diff --git a/src/ataTest.c b/src/ataTest.c
new file mode 100644
index 0000000..b8156e7
--- /dev/null
+++ b/src/ataTest.c
@@ -0,0 +1,122 @@
+#include "ktest.h"
+#include "ata.h"
+#include "string.h"
+
+/*
+ * Real hardware coverage for the ATA PIO driver: these tests run against
+ * whatever drive QEMU actually attaches on the primary IDE bus (see
+ * tools/ci-test.sh / Makefile for the -drive flag), so a wiring mistake in
+ * ata.c (wrong port, wrong status bit, off-by-one in the LBA registers)
+ * shows up as a real read/write mismatch here, not as a mocked assertion.
+ */
+
+static void fillPattern(uint8* buf, uint64 seed)
+{
+    for (int i = 0; i < ataSectorSize; i++)
+        buf[i] = (uint8)((seed * 7 + (uint64)i * 13) & 0xFF);
+}
+
+KTEST(ataDrivePresent)
+{
+    KT_TRUE(t, ataPresent());
+    KT_GT(t, ataSectorCount(), 0);
+
+    const char* model = ataModelString();
+    KT_NOTNULL(t, model);
+    KT_TRUE(t, strlen(model) > 0);
+}
+
+KTEST(ataSingleSectorRoundTrip)
+{
+    uint8 out[ataSectorSize];
+    uint8 in[ataSectorSize];
+    fillPattern(out, 0xA5);
+
+    KT_TRUE(t, ataWriteSectors(10, 1, out));
+    memset(in, 0, sizeof(in));
+    KT_TRUE(t, ataReadSectors(10, 1, in));
+    KT_EQ(t, memcmp(in, out, ataSectorSize), 0);
+}
+
+KTEST(ataOverwriteReflectsLatestData)
+{
+    uint8 first[ataSectorSize];
+    uint8 second[ataSectorSize];
+    uint8 back[ataSectorSize];
+    fillPattern(first, 0x11);
+    fillPattern(second, 0x99);
+
+    KT_TRUE(t, ataWriteSectors(11, 1, first));
+    KT_TRUE(t, ataWriteSectors(11, 1, second));
+    KT_TRUE(t, ataReadSectors(11, 1, back));
+    KT_EQ(t, memcmp(back, second, ataSectorSize), 0);
+    KT_NE(t, memcmp(back, first, ataSectorSize), 0);
+}
+
+KTEST(ataAdjacentSectorsDoNotCrossTalk)
+{
+    uint8 a[ataSectorSize];
+    uint8 b[ataSectorSize];
+    uint8 backA[ataSectorSize];
+    uint8 backB[ataSectorSize];
+    fillPattern(a, 0x30);
+    fillPattern(b, 0x77);
+
+    KT_TRUE(t, ataWriteSectors(20, 1, a));
+    KT_TRUE(t, ataWriteSectors(21, 1, b));
+    KT_TRUE(t, ataReadSectors(20, 1, backA));
+    KT_TRUE(t, ataReadSectors(21, 1, backB));
+    KT_EQ(t, memcmp(backA, a, ataSectorSize), 0);
+    KT_EQ(t, memcmp(backB, b, ataSectorSize), 0);
+    KT_NE(t, memcmp(backA, backB, ataSectorSize), 0);
+}
+
+KTEST(ataMultiSectorRoundTrip)
+{
+    #define ataTestSectors 4
+    uint8 out[ataTestSectors * ataSectorSize];
+    uint8 in[ataTestSectors * ataSectorSize];
+
+    for (int s = 0; s < ataTestSectors; s++)
+        fillPattern(out + s * ataSectorSize, (uint64)(0x40 + s));
+
+    KT_TRUE(t, ataWriteSectors(30, ataTestSectors, out));
+    memset(in, 0, sizeof(in));
+    KT_TRUE(t, ataReadSectors(30, ataTestSectors, in));
+
+    for (int s = 0; s < ataTestSectors; s++)
+        KT_EQ(t, memcmp(in + s * ataSectorSize, out + s * ataSectorSize, ataSectorSize), 0);
+    #undef ataTestSectors
+}
+
+KTEST(ataLastSectorIsAddressable)
+{
+    uint64 last = ataSectorCount() - 1;
+    uint8 out[ataSectorSize];
+    uint8 in[ataSectorSize];
+    fillPattern(out, 0xEE);
+
+    KT_TRUE(t, ataWriteSectors(last, 1, out));
+    KT_TRUE(t, ataReadSectors(last, 1, in));
+    KT_EQ(t, memcmp(in, out, ataSectorSize), 0);
+}
+
+KTEST(ataOutOfRangeRequestsAreRejected)
+{
+    uint8 buf[ataSectorSize];
+    KT_FALSE(t, ataReadSectors(ataSectorCount(), 1, buf));
+    KT_FALSE(t, ataWriteSectors(ataSectorCount(), 1, buf));
+
+    /* Buffer is sized for 2 sectors: if the bounds check were buggy and let
+       this through, it would prove itself by corrupting the canary sector
+       instead of silently passing. */
+    uint8 twoSectors[2 * ataSectorSize];
+    KT_FALSE(t, ataReadSectors(ataSectorCount() - 1, 2, twoSectors));
+}
+
+KTEST(ataZeroLengthRequestIsNoop)
+{
+    uint8 buf[ataSectorSize];
+    KT_TRUE(t, ataReadSectors(0, 0, buf));
+    KT_TRUE(t, ataWriteSectors(0, 0, buf));
+}