Windows BSOD Error 0x00000045 — What It Means & How to Fix It

What Does This Error Mean?

BSOD 0x00000045 (INSUFFICIENT_SYSTEM_MAP_REGS) means Windows ran out of map registers — small hardware resources that DMA (Direct Memory Access) devices use to transfer data directly to RAM. When too many devices try to map too much memory at once, and the hardware adapter runs out of map registers, this fatal error occurs. It is most often caused by a faulty or poorly written driver requesting far more map registers than it actually needs.

Affected Models

Windows 10
Windows 11
Windows 8.1
Windows 7

Common Causes

A device driver has a memory mapping bug — it requests far more DMA map registers than necessary
Multiple high-throughput devices (such as network adapters, storage controllers, and GPU) are competing for limited map register resources
An outdated driver is not efficiently managing DMA resources the way modern Windows versions expect
Faulty DMA-capable hardware is requesting excessive memory mappings due to an internal error
A 32-bit driver running on a 64-bit system is using legacy DMA addressing that wastes map register resources

How to Fix It

Update all device drivers — especially for network adapters, storage controllers, and graphics cards. Open Device Manager (right-click Start > Device Manager). Right-click each device under these categories and select 'Update driver.' Also visit your motherboard manufacturer's website for chipset driver updates.

DMA map register exhaustion is almost always a driver efficiency problem. Newer driver versions typically handle DMA resource allocation much more carefully.
Use WhoCrashed to identify the specific driver causing the problem. Download it free from resplendence.com. After the next crash, open WhoCrashed — it reads your C:\Windows\Minidump files and names the driver responsible. Focus your updates on that specific driver.

This error can be caused by any DMA-capable device's driver. Knowing exactly which one saves you from updating every driver on the system unnecessarily.
Remove recently added expansion cards or PCIe devices. If you recently installed a new network card, capture card, storage controller, or any other expansion card, try removing it and see if the crashes stop. The new device's driver may be the DMA resource hog.

New PCIe devices add DMA-capable hardware to your system. If the combined DMA demand from all devices exceeds the chipset's map register allocation, this crash occurs.
Update your system BIOS. Visit your motherboard manufacturer's website (ASUS, MSI, Gigabyte, ASRock, Dell, HP, etc.) and find your exact model. Download and apply the latest BIOS update. BIOS updates sometimes increase DMA resource allocation and fix chipset-level resource shortage bugs.

BIOS updates are more complex than regular software updates — follow the manufacturer's instructions exactly. Interrupting a BIOS update can damage your motherboard.
Check for 32-bit drivers on a 64-bit system. Open Device Manager, click View > Show hidden devices. Look for any devices showing a 32-bit or legacy driver warning. 32-bit DMA drivers on 64-bit Windows use older addressing models that consume more map registers. Replace or update these drivers with 64-bit versions.

Legacy 32-bit drivers are increasingly incompatible with modern Windows. If a device only has 32-bit drivers and the manufacturer has abandoned it, the device itself may need to be replaced.

When to Call a Professional

This is a rare and complex error. If updating drivers does not resolve it, a technician with kernel debugging capabilities can analyse DMA allocation logs to find the exact driver wasting map registers. In some cases, a hardware component needs to be replaced.

Frequently Asked Questions

What is DMA and why does it need map registers?

DMA (Direct Memory Access) lets hardware devices like network cards and storage controllers move data directly to your computer's RAM without involving the CPU. This is much faster than making the CPU handle every data transfer. Map registers are small hardware resources that help the DMA hardware translate between device memory addresses and system RAM addresses. When a driver requests too many of them at once, there are none left for other devices, causing this crash.

I have a lot of USB and PCIe devices. Is that the cause?

It can be. Each DMA-capable device needs map registers to operate. A system with many high-bandwidth devices (multiple storage controllers, fast network cards, capture cards, etc.) can exhaust the available pool. Try disabling or removing devices you do not use often and see if the crashes stop. Updating all drivers to the most efficient versions also reduces per-device map register consumption.

Could upgrading from Windows 10 to Windows 11 trigger this?

Yes — if any of your existing drivers were not updated for Windows 11 compatibility, they may use less efficient DMA resource management. Check that all drivers were updated after the upgrade. Also check the Windows 11 compatibility information for all your hardware — some older devices have known DMA issues under Windows 11 that require specific driver versions or have no fix available.