diff --git a/src/ata.c b/src/ata.c
new file mode 100644
index 0000000..658b15c
--- /dev/null
+++ b/src/ata.c
@@ -0,0 +1,199 @@
+#include "ata.h"
+#include "ports.h"
+
+#define ataRegData      0x1F0
+#define ataRegError     0x1F1
+#define ataRegSectorCnt 0x1F2
+#define ataRegLbaLow    0x1F3
+#define ataRegLbaMid    0x1F4
+#define ataRegLbaHigh   0x1F5
+#define ataRegDriveHead 0x1F6
+#define ataRegStatus    0x1F7
+#define ataRegCommand   0x1F7
+#define ataRegControl   0x3F6
+
+#define ataStatusErr 0x01
+#define ataStatusDrq 0x08
+#define ataStatusDf  0x20
+#define ataStatusBsy 0x80
+
+#define ataCmdReadSectors  0x20
+#define ataCmdWriteSectors 0x30
+#define ataCmdCacheFlush   0xE7
+#define ataCmdIdentify     0xEC
+
+#define ataMaxSectorsPerCommand 255
+#define ataPollTimeout 1000000u
+
+static bool diskPresent;
+static uint64 totalSectors;
+static char modelBuffer[41];
+
+static void ataIoDelay(void)
+{
+    /* Selecting a drive needs ~400ns to settle; reading the alternate
+       status register is a documented no-op read that burns exactly that
+       long without disturbing the main status register. */
+    inb(ataRegControl);
+    inb(ataRegControl);
+    inb(ataRegControl);
+    inb(ataRegControl);
+}
+
+static bool ataWaitClear(uint8 mask)
+{
+    for (uint32 i = 0; i < ataPollTimeout; i++)
+        if (!(inb(ataRegStatus) & mask))
+            return true;
+    return false;
+}
+
+static bool ataWaitDrqOrErr(bool* err)
+{
+    for (uint32 i = 0; i < ataPollTimeout; i++) {
+        uint8 status = inb(ataRegStatus);
+        if (status & (ataStatusErr | ataStatusDf)) {
+            *err = true;
+            return true;
+        }
+        if (status & ataStatusDrq) {
+            *err = false;
+            return true;
+        }
+    }
+    return false;
+}
+
+static void ataSelect(uint64 lba, uint8 count)
+{
+    outb(ataRegDriveHead, (uint8)(0xE0 | ((lba >> 24) & 0x0F)));
+    ataIoDelay();
+    outb(ataRegSectorCnt, count);
+    outb(ataRegLbaLow, (uint8)(lba & 0xFF));
+    outb(ataRegLbaMid, (uint8)((lba >> 8) & 0xFF));
+    outb(ataRegLbaHigh, (uint8)((lba >> 16) & 0xFF));
+}
+
+bool ataInit(void)
+{
+    diskPresent = false;
+    totalSectors = 0;
+    modelBuffer[0] = 0;
+
+    outb(ataRegControl, 0x02); /* nIEN: this driver only ever polls */
+
+    outb(ataRegDriveHead, 0xA0); /* master, no chs/lba bits needed yet */
+    ataIoDelay();
+    outb(ataRegSectorCnt, 0);
+    outb(ataRegLbaLow, 0);
+    outb(ataRegLbaMid, 0);
+    outb(ataRegLbaHigh, 0);
+    outb(ataRegCommand, ataCmdIdentify);
+
+    if (inb(ataRegStatus) == 0)
+        return false; /* floating bus: no drive wired up on this channel */
+
+    if (!ataWaitClear(ataStatusBsy))
+        return false;
+
+    /* A plain PATA hard disk leaves LBA mid/high at 0 after IDENTIFY; an
+       ATAPI or SATA-bridge device stamps a signature there instead. This
+       driver only supports the former. */
+    if (inb(ataRegLbaMid) != 0 || inb(ataRegLbaHigh) != 0)
+        return false;
+
+    bool err = false;
+    if (!ataWaitDrqOrErr(&err) || err)
+        return false;
+
+    uint16 identifyWords[256];
+    for (int i = 0; i < 256; i++)
+        identifyWords[i] = inw(ataRegData);
+
+    totalSectors = (uint64)identifyWords[60] | ((uint64)identifyWords[61] << 16);
+
+    for (int i = 0; i < 20; i++) {
+        uint16 word = identifyWords[27 + i];
+        modelBuffer[i * 2] = (char)(word >> 8);
+        modelBuffer[i * 2 + 1] = (char)(word & 0xFF);
+    }
+    modelBuffer[40] = 0;
+    for (int i = 39; i >= 0 && modelBuffer[i] == ' '; i--)
+        modelBuffer[i] = 0;
+
+    diskPresent = totalSectors > 0;
+    return diskPresent;
+}
+
+bool ataPresent(void)
+{
+    return diskPresent;
+}
+
+uint64 ataSectorCount(void)
+{
+    return totalSectors;
+}
+
+const char* ataModelString(void)
+{
+    return modelBuffer;
+}
+
+bool ataReadSectors(uint64 lba, uint32 count, void* buffer)
+{
+    if (count == 0)
+        return true;
+    if (!diskPresent || count > ataMaxSectorsPerCommand || lba + count > totalSectors)
+        return false;
+
+    if (!ataWaitClear(ataStatusBsy))
+        return false;
+    ataSelect(lba, (uint8)count);
+    outb(ataRegCommand, ataCmdReadSectors);
+
+    uint16* dst = (uint16*)buffer;
+    for (uint32 s = 0; s < count; s++) {
+        if (!ataWaitClear(ataStatusBsy))
+            return false;
+        bool err = false;
+        if (!ataWaitDrqOrErr(&err) || err)
+            return false;
+        for (int w = 0; w < 256; w++)
+            dst[w] = inw(ataRegData);
+        dst += 256;
+    }
+    return true;
+}
+
+bool ataWriteSectors(uint64 lba, uint32 count, const void* buffer)
+{
+    if (count == 0)
+        return true;
+    if (!diskPresent || count > ataMaxSectorsPerCommand || lba + count > totalSectors)
+        return false;
+
+    if (!ataWaitClear(ataStatusBsy))
+        return false;
+    ataSelect(lba, (uint8)count);
+    outb(ataRegCommand, ataCmdWriteSectors);
+
+    const uint16* src = (const uint16*)buffer;
+    for (uint32 s = 0; s < count; s++) {
+        if (!ataWaitClear(ataStatusBsy))
+            return false;
+        bool err = false;
+        if (!ataWaitDrqOrErr(&err) || err)
+            return false;
+        for (int w = 0; w < 256; w++)
+            outw(ataRegData, src[w]);
+        src += 256;
+        ataIoDelay();
+    }
+
+    outb(ataRegCommand, ataCmdCacheFlush);
+    if (!ataWaitClear(ataStatusBsy))
+        return false;
+
+    return true;
+}