Resource Cheatsheet
A+ Core 1 3.5: CPU Features
A+ Core 1 3.5 — 32-bit vs 64-bit (x86/x64), ARM architecture, and multi-core CPUs.
- Updated
- Reading time
- 3 min read
- Detail
- A+ Core 1
- Detail
- CPU Features
On this page
In one line: 64-bit CPUs (x64) address far more memory than 32-bit (x86) and run 32-bit apps too; ARM is the efficient licensed architecture behind phones and more PCs; and one CPU holds many parallel cores.
Companion to: Professor Messer A+ Core 1 (220-1201), Section 3, objective 3.5. The full version is the CPU Features class notes; the section overview is the Section 3 sheet.
32-bit vs 64-bit
| 32-bit (x86) | 64-bit (x64) | |
|---|---|---|
| Address space | 2^32 | 2^64 |
| Memory reach | ~4 GB (Windows: ~3.25 GB usable) | ~17 billion GB (16 EB) |
| Also called | x86 (from the 8086) | x86-64 / AMD64 |
| Drivers | 32-bit drivers | 64-bit drivers |
| Apps | Can’t run 64-bit apps | Can run 32-bit apps |
| Windows folder | Program Files (x86) | Program Files |
- One-way rule: 64-bit runs 32-bit, but 32-bit can’t run 64-bit.
- Check it:
$env:PROCESSOR_ARCHITECTURE(PS) ·uname -m(Bash) ·echo %PROCESSOR_ARCHITECTURE%(CMD) → AMD64 / x86 / ARM64.
ARM
| Aspect | Detail |
|---|---|
| Name | Advanced RISC Machine (RISC = Reduced Instruction Set Computing) |
| Model | ARM Limited designs the spec and licenses it to third parties |
| Strengths | Less power, less heat, fast |
| Where | ~99% of phones; growing in laptops/desktops (Apple Silicon, Windows on ARM) |
CPU cores
- One CPU package holds multiple cores; each core has its own logic + cache.
- Multiple cores = instructions run in parallel → more throughput. Rated by count (8-core, 16-core).
- Beyond scope: L1/L2 per core, L3 shared; threads (SMT/Hyper-Threading) show one core as two logical CPUs.
🔐 Security notes
- 64-bit is better defended, not just bigger: 64-bit Windows enforces driver signing, kernel patch protection (PatchGuard), and stronger DEP/ASLR. A 32-bit OS is usually older and missing these — a larger attack surface.
- Architecture decides what runs — malware built for x86/x64/ARM only runs there; emulation layers (Windows on ARM, Rosetta) are an extra layer to account for.
- Shared core caches enable side channels (Spectre/Meltdown family) — keep CPU microcode/firmware and the OS patched.
Practice drills
1. How much memory can 32-bit vs 64-bit address?
32-bit ≈ 4 GB (2^32); 64-bit ≈ 17 billion GB (2^64 = 16 EB).
2. What do x86 and x64 mean?
x86 = 32-bit (from the 8086); x64 = 64-bit (also x86-64 / AMD64).
3. State the app compatibility rule.
A 64-bit OS can run 32-bit apps; a 32-bit OS cannot run 64-bit apps.
4. Where do 32-bit vs 64-bit apps install in Windows?
32-bit → Program Files (x86); 64-bit → Program Files.
5. What does ARM stand for, and what does ARM Limited do?
Advanced RISC Machine; ARM Limited designs the spec and licenses it to third parties.
6. Why are ARM chips popular in phones?
They’re efficient — less power and heat, fast — so ~99% of phones use them.
7. What does each CPU core contain, and why do more cores help?
Its own processing logic and cache; multiple cores execute instructions simultaneously.
Key takeaways
- 64-bit (x64) addresses ~17 billion GB vs 32-bit (x86) ~4 GB; drivers must match the OS.
- 64-bit runs 32-bit apps; 32-bit can’t run 64-bit. Program Files vs Program Files (x86).
- ARM = Advanced RISC Machine (licensed by ARM Limited) — efficient, ~99% of phones, growing in PCs.
- Cores = independent processors in one package with their own cache → parallel execution.
- Security: 64-bit adds enforced driver signing, PatchGuard and stronger DEP/ASLR — moving off 32-bit is a security win.