Parity bits are far from useless. They are frequently used to
implement single-error correction, double-error detection per 8 bytes.
Why do you think this here Alpha has a 144-bit wide memory bus?
Gratuitous exciting extract from the doc:
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ECC Syndrome Codes (Sorted by Data Bits)
Data Bit/ Data Bit/ Data Bit/ Data Bit/ Check Bit/
Syn Code Syn Code Syn Code Syn Code Syn Code
0 / CE 16 / 0E 32 / 4F 48 / 8F 0 / 01
1 / CB 17 / 0B 33 / 4A 49 / 8A 1 / 02
2 / D3 18 / 13 34 / 52 50 / 92 2 / 04
3 / D5 19 / 15 35 / 54 51 / 94 3 / 08
4 / D6 20 / 16 36 / 57 52 / 97 4 / 10
5 / D9 21 / 19 37 / 58 53 / 98 5 / 20
6 / DA 22 / 1A 38 / 5B 54 / 9B 6 / 40
7 / DC 23 / 1C 39 / 5D 55 / 9D 7 / 80
8 / 23 24 / E3 40 / A2 56 / 62
9 / 25 25 / E5 41 / A4 57 / 64
10 / 26 26 / E6 42 / A7 58 / 67
11 / 29 27 / E9 43 / A8 59 / 68
12 / 2A 28 / EA 44 / AB 60 / 6B
13 / 2C 29 / EC 45 / AD 61 / 6D
14 / 31 30 / F1 46 / B0 62 / 70
15 / 34 31 / F4 47 / B5 63 / 75
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Rob.