GMA86 - Revision history

Enigma at 22:15, 28 August 2026

2026-08-28T22:15:43Z

Enigma at 20:07, 28 August 2026

2026-08-28T20:07:49Z

Enigma at 00:52, 28 August 2026

2026-08-28T00:52:55Z

Enigma at 00:51, 28 August 2026

2026-08-28T00:51:09Z

Show changes

Enigma at 00:19, 28 August 2026

2026-08-28T00:19:35Z

Enigma at 23:14, 27 August 2026

2026-08-27T23:14:32Z

Enigma: Created page with "Descriptions needs to be done. ==== Pages that refer to this protection ==== {{Special:Whatlinkshere/GMA86}}"

2019-10-27T18:16:35Z

Created page with "Descriptions needs to be done. ==== Pages that refer to this protection ==== {{Special:Whatlinkshere/GMA86}}"

New page

Descriptions needs to be done.

==== Pages that refer to this protection ====

{{Special:Whatlinkshere/GMA86}}

@@ Line 39: / Line 39: @@
 title uses:
-# '''Track 38''' (<code>$26</code>) — '''C64-side bulk decrypt.'''
+# '''Track 38''' (<code>$26</code>) — '''C64-side bulk decrypt.''' The measured byte is sent to the C64 over a raster-synced <code>$DD00</code> handshake and used as a single repeating-byte XOR key over almost the entire game, decrypted in place in one pass before jumping straight into the result. Seven of eleven surveyed titles: Sanxion, Split Personalities, Cyrus II Chess, The Sentry, Filemaster 64, Pub Games, and The Graphic Adventure Creator.
-  The measured byte is sent to the C64 over a raster-synced <code>$DD00</code>
+# '''Track 39''' (<code>$27</code>) — '''drive-side per-sector decrypt.''' The measured byte is instead baked as a literal <code>EOR #imm</code> operand into a second, freshly-uploaded drive-resident program, and the 1541's own 6502 decrypts every subsequent sector before it ever reaches the C64, streaming the result out over a bit-banged serial link one byte at a time. Three of eleven surveyed titles, all Hewson-published: Firelord, Uridium, and Iridis Alpha — matching GMA87's Eagles almost byte-for-byte, including the identical <code>$035C</code>/<code>$035D</code> key-injection address.
-  handshake and used as a single repeating-byte XOR key over almost the
+# '''Track 37''' (<code>$25</code>) — '''presence-only, no key.''' The drive reads two raw 256-byte blocks off the track and reports success unconditionally; nothing is ever folded, compared, or sent. This is the ancestral [[GMA85]] mechanism, carried forward unmodified. One of eleven surveyed titles: Robin of the Wood, whose disk-label date (<code>gma140486</code>) places it firmly within the GMA86 era despite running GMA85-generation drive code.
 On any genuine failure — marker not found within the retry budget, or a

@@ Line 55: / Line 55: @@
    including the identical <code>$035C</code>/<code>$035D</code>
    key-injection address.
-# '''Track 37''' (<code>$25</code>) — '''presence-only, no key.''' The
+# '''Track 37''' (<code>$25</code>) — '''presence-only, no key.'''
-   drive reads two raw 256-byte blocks off the track and reports success
+   The drive reads two raw 256-byte blocks off the track and reports success
    unconditionally; nothing is ever folded, compared, or sent. This is the
    ancestral [[GMA85]] mechanism, carried forward unmodified. One of eleven
@@ Line 67: / Line 67: @@
 rather than reporting an error the C64 could act on, the same "hang, never
 produce wrong output" convention used throughout the whole GMA family.
 == Signature measurement: the shared drive-side routine ==

@@ Line 39: / Line 39: @@
 title uses:
-# '''Track 38''' (<code>$26</code>) — '''C64-side bulk decrypt.''' The
+# '''Track 38''' (<code>$26</code>) — '''C64-side bulk decrypt.'''
-   measured byte is sent to the C64 over a raster-synced <code>$DD00</code>
+   The measured byte is sent to the C64 over a raster-synced <code>$DD00</code>
    handshake and used as a single repeating-byte XOR key over almost the
    entire game, decrypted in place in one pass before jumping straight into

@@ Line 1: / Line 1: @@
-[[GMA86 Robin of the Wood]]
+= Pages that refer to this protection =
-==== Pages that refer to this protection ====
+= Description =
+An exception is [[Robin of the Wood]], that shows GMA86, but uses the same protection code as GMA85.