vault backup: 2024-01-22 12:22:45

Semester 2/Computer Systems Internals & Linux/Week 1/Week 2 Computer Systems Internals.md

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+# Clock Drift
+
+Recalibrate clocks when out of sync:
+
+- Async Transmission
+	- Send a small amount of data, then 1, then 0, then some more data.
+- Manchester Encoding
+	- Send each bit as 2 values
+	- Original 10MBase-T uses this
+- HDB3 encoding
+	- 3 logic levels to ensure no static sequences
+	- Used for long distance cables
+- 4B5B encoding
+	- Transmit 5 bits of signalling to represent 4 bits of data
+	- 100MBase-T uses this.
+
+# Quantities in Digital Communication
+
+## Bit
+
+- Short for "binary digit". Byte = 8 bits
+
+## Data Rate
+
+- Bits per second
+
+## Baud Rate
+
+- Times per second the transmitted signal changes.
+
+### Examples
+
+- A modem used for dialup will encode at least six bits of data for each unit of signalling.
+- Ethernet uses between 1.2 and 2 units of signalling per bit of data.
+
+# Text Encoding Communication
+
+- The word "Up" -> ASCII is 85, 112
+- Binary stream -> 010101010110000
+This demonstrates the worst case scenario for 4B5B, and 4 zeros to demonstrate HDB3.