The hard disk capacity in a CPU refers to the amount of data that can be stored on the hard disk drive that is integrated into the central processing unit. The CPU is the main component that processes instructions and performs calculations in a computer. Modern CPUs often contain a small hard disk drive built right onto the main circuit board.
Why Do CPUs Have a Hard Disk?
There are a few key reasons why hard disks are included on the CPU itself:
- Cache data – The hard disk can act as a data cache to store frequently used data and instructions closer to the CPU for faster access.
- Boot drive – Many CPUs use their integrated hard disk as the primary boot drive to load the operating system.
- Configuration data – Settings, firmware, and other low-level data can be stored on the CPU’s hard disk.
Integrating some hard disk capacity directly into the CPU can improve performance compared to relying solely on external hard disks or solid state drives. The key advantage is the close proximity to the CPU cores, allowing very rapid access to cached data.
Typical Capacities
Most modern CPUs include relatively small hard drives, typically in the range of 16 GB to 128 GB. For example, Intel’s Skylake and Kaby Lake CPUs include options for 16 GB, 32 GB, 64 GB, and 128 GB drives. AMD’s Ryzen Embedded V1000 models can be configured with 32 GB to 128 GB of onboard eMMC drive storage.
The capacities used are a tradeoff between cost, size, and performance. Even a drive as small as 16 GB is sufficient for caching boot data sets, firmware, and other low-level CPU functionality. Larger capacities in the 64 GB to 128 GB range allow extensive caching of programs and data for much faster access.
Access Speed Advantages
The close integration of a hard disk drive directly into the CPU packaging provides very fast access speeds. This allows data to be streamed into the CPU cores at near memory-like speeds. Approximately 250 – 500 MB/s read speeds are common for SATA-based CPUs hard drives communicating over the internal bus interfaces.
In comparison, a traditional external hard drive using SATA 3 or USB 3.0 interfaces will be limited to approximately 550 MB/s for sequential reads. So an internal CPU hard disk can match and even exceed the speeds of external drives.
Reliability Considerations
Reliability is a key consideration for CPU integrated hard disks, since a failure could cripple the system. However, CPU hard drives typically use high-reliability flash memory-based disks rather than mechanical platters. Flash drives have far better shock resistance, lower failure rates, and reduced heat output compared to traditional hard disk drives.
The onboard CPU hard disk is typically treated as an ancillary drive, with critical data still stored on external SSDs or RAID arrays for redundancy. The CPU drive stores expendable cached data and low-level boot and firmware information.
Intel CPUs With Hard Drives
Here are some examples of Intel CPUs that include onboard hard disk capacities:
| CPU Model | Capacity |
| Intel Core i3-8121U | 64 GB eMMC |
| Intel Atom x5-E3940 | 32 GB eMMC |
| Intel Core i5-7360U | 16 GB SSD |
AMD CPUs With Hard Drives
Here are some AMD CPUs with integrated hard drives:
| CPU Model | Capacity |
| AMD Ryzen V1605B | 128 GB SSD |
| AMD Ryzen V1202B | 64 GB eMMC |
| AMD GX-412HC SOC | 32 GB eMMC |
Benchmarks
One of the key performance advantages of an internal CPU hard disk is the very fast access for random I/O operations. Typical benchmarks for 4k random read speed can be:
- CPU internal HD: 1500 IOPS
- External SSD over SATA 3: 100 IOPS
- External HDD over USB 3.0: 10-20 IOPS
So the CPU’s hard disk is 10-15x faster compared to an external SSD and up to 100x faster than an external hard disk drive. This speed advantage is very significant for small I/O operations used in caching and boot scenarios.
Size and Form Factors
CPU hard drives use compact form factors designed specifically for integration into the restricted space of the CPU package. Common types of drives used include:
- mSATA – mini-SATA SSD drives in a compact rectangular form factor.
- M.2 – M.2 SSD module in a thin, long stick layout.
- eMMC – embedded MMC flash drive with a ball grid array interface.
These tiny drive form factors allow capacities ranging from 8 GB up to 512 GB to be fitted onto the CPU motherboard. The compact footprint is a key advantage compared to standard 2.5″ or 3.5″ hard drives.
Conclusion
In summary, the hard disk capacity integrated directly into modern CPUs provides three key advantages:
- Faster access speeds – Up to 500 MB/s bandwidth and over 100x faster random I/O compared to external drives.
- Hardware integration – The drive is packaged directly with the CPU cores for close data proximity.
- Compact footprint – Small drive form factors like mSATA allow high capacities despite tight space constraints.
CPU hard drives are optimized for caching frequently used data sets, storing firmware and boot data, and other tasks benefiting from very fast storage access. Typical capacities range from 16 GB to 128 GB.