38911 Bytes Free? Commodore 64's BASIC RAM

Published: 13 December 2023
on channel: 8-Bit Show And Tell

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The Commodore 64's famous blue-on-blue boot message says "38911 BASIC BYTES FREE". But it's supposedly a 64K RAM system, so where did the rest of the RAM go? Is it a scam? We go through the origin of the name Commodore 64, discuss how 64K of RAM was a pretty big deal in 1982, and then get into the details of the C64 memory map. Then we track down why we have 1 or 3 bytes less than a full 38K of RAM, depending on who you ask.

The books I show are "20 GOTO 10: 10101001 facts about retro computers" by Steven Goodwin, and "On The Edge: The Spectacular Rise and Fall of Commodore" by Brian Bagnall. The memory map inserts are from "The Commodore 64 Programmer's Reference Guide".

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Links:
VIC-30 Video:    • The VIC-10 & VIC-30: Commodore UK's C...

Index:
0:00 Questions about 38911 bytes free
1:57 How much RAM in 1982
5:05 Commodore 64 = 64 KB DRAM
7:37 C64 Memory map - where does it go?
11:11 16-bit addressing, bank switching
13:40 Plus/4 and MSX: Constraints common!
15:08 38K = 38912, not 38911! Location 2048
19:37 FRE(0)+2^16 = 38909 why??
23:18 Machine Language Monitor - Super Snappy time
26:57 Conclusion and thanks!

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