Computer Fundamentals on Chen Kai Blog

Computer Fundamentals: Deep Dive and System Integration

Sat, 14 Jan 2023 09:00:00 +0000

We’ve spent five chapters opening one box at a time — the CPU, the cache hierarchy, storage, the motherboard and GPU, the network and power supply. Each part is interesting on its own, but a computer is not its components. A computer is what happens when those components have to agree, every nanosecond, on what to do next.

This finale is about that conversation. We’ll wire everything together into a single picture, look at the system through the eyes of a profiler, revisit the 80-year-old design tension that still shapes every chip you buy, and end by looking forward — chiplets, photonic interconnects, and the quietly arriving quantum era.

Computer Fundamentals: Network, Power, and Troubleshooting

Sat, 24 Dec 2022 09:00:00 +0000

Why does the gigabit NIC on your motherboard sometimes negotiate down to 100 Mbps? Why does a brand-new build with a 650 W “Gold” PSU randomly reboot under heavy GPU load? Why does the room next to the server rack always feel warm? These are the everyday consequences of two systems that most people never look at: the network I/O pipeline and the power-and-cooling chain that keeps the silicon alive.

Computer Fundamentals: Motherboard, Graphics, and Expansion

Sat, 03 Dec 2022 09:00:00 +0000

A modern desktop motherboard is an unusually honest object. Every important design decision — how many PCIe lanes the CPU exposes, which slots are wired straight to the CPU and which tunnel through the chipset, how the VRM is sized to feed a 250 W processor, why the second long PCIe slot only runs at ×4 — is laid out in plain copper on the PCB. If you can read the board, you can predict almost every performance cliff a user will hit. This fourth instalment of the Computer Fundamentals Deep Dive Series teaches that reading skill, then turns it inward to the GPU, where the same lesson applies in miniature: a GPU is a chip whose entire architecture exists to keep thousands of arithmetic lanes fed with data, and almost everything else — caches, schedulers, tensor cores, HBM stacks — is in service of that goal.

Computer Fundamentals: Storage Systems (HDD vs SSD)

Sat, 12 Nov 2022 09:00:00 +0000

Why can a single SSD swap “resurrect” a five-year-old laptop? Why does a TLC drive rated for only 1 000 P/E cycles still last more than a decade for normal users? Why does a brand-new SSD that benchmarks at 3 500 MB/s sometimes collapse to 50 MB/s after a few weeks? This third instalment of the Computer Fundamentals Deep Dive Series answers those questions from first principles. We will look at how rotating magnetic platters compare with charge-trap NAND cells, how the bandwidth of an interface (SATA, PCIe Gen 3/4/5) interacts with the parallelism of a protocol (AHCI vs NVMe), how RAID levels trade capacity for fault tolerance, how a file system organises bytes on a raw block device, and how to keep all of this fast and safe in production.

Computer Fundamentals: Memory and Cache Systems

Sat, 22 Oct 2022 09:00:00 +0000

A CPU core can complete a multiplication in roughly 0.3 ns. A spinning hard disk needs 10 ms to seat its head over a sector. Between those two numbers sits a factor of about 30 million. Every line of memory engineering — caches, DRAM cells, page tables, TLBs, ECC, NUMA, channels — is a coordinated answer to that single, brutal asymmetry.

This is part 2 of the Computer Fundamentals Deep Dive. We will not stop at “DDR is fast and RAM is volatile”. We will trace a single load instruction from the CPU pipeline through the L1, L2, L3 caches, the TLB, the page table, the memory controller, the channels, and finally the DRAM cells themselves — and look at what each layer is actually doing, and why.

Computer Fundamentals: CPU and the Computing Core

Sat, 01 Oct 2022 09:00:00 +0000

Why does your 100 Mbps internet only download at about 12 MB/s? Why does a “1 TB” hard drive show only 931 GB in Windows? Why does a 32-bit system top out around 3.2 GB of usable RAM? And what actually happens, cycle by cycle, when the CPU runs your code?

This is part 1 of the Computer Fundamentals series. We start from bits and bytes, then go down into the CPU itself: pipelines, caches, branch prediction, out-of-order execution, multiple cores, and SMT. By the end you should be able to read a CPU spec sheet — or a perf profile — and know what each number is paying for.