GMA85 - Revision history

Enigma at 22:12, 28 August 2026

2026-08-28T22:12:35Z

Enigma at 20:11, 28 August 2026

2026-08-28T20:11:26Z

Enigma at 00:43, 28 August 2026

2026-08-28T00:43:50Z

Enigma at 00:42, 28 August 2026

2026-08-28T00:42:38Z

Enigma at 00:36, 28 August 2026

2026-08-28T00:36:09Z

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Enigma at 00:21, 28 August 2026

2026-08-28T00:21:39Z

Enigma at 00:21, 28 August 2026

2026-08-28T00:21:17Z

Enigma at 00:17, 28 August 2026

2026-08-28T00:17:56Z

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Enigma at 00:14, 28 August 2026

2026-08-28T00:14:50Z

Enigma: Created page with "Descriptions needs to be done. ==== Pages that refer to this protection ==== {{Special:Whatlinkshere/GMA85}}"

2021-01-05T21:05:57Z

Created page with "Descriptions needs to be done. ==== Pages that refer to this protection ==== {{Special:Whatlinkshere/GMA85}}"

New page

Descriptions needs to be done.

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

{{Special:Whatlinkshere/GMA85}}

@@ Line 35: / Line 35: @@
 C64 — perform the check:
-# The drive seeks an out-of-range track — '''track 37''' in every GMA85
+# The drive seeks an out-of-range track — '''track 37''' in every GMA85 title found so far, one track short of GMA86/87's Cholo/Triaxos (38) and Eagles/Firelord/Uridium/Iridis Alpha (39).
-  title found so far, one track short of GMA86/87's Cholo/Triaxos (38) and
+# It searches for a short, deliberately non-standard byte marker (<code>$69</code> ... <code>$A9</code>, byte-aligned to the raw GCR shift register rather than the usual 5-bit nibble boundaries — the same marker convention used across the whole GMA family) with a 90-attempt retry budget.
-  Eagles/Firelord/Uridium/Iridis Alpha (39).
+# On a match, it reads two raw 256-byte blocks off the disk into its own RAM.
-# It searches for a short, deliberately non-standard byte marker
+# It reports success to the C64 unconditionally — the two blocks it just read are never folded into a value, compared against anything, or sent anywhere. They are simply discarded.
-  (<code>$69</code> ... <code>$A9</code>, byte-aligned to the raw GCR
+# The C64 continues loading regardless of what (if anything) was in those blocks. On a genuine failure — no out-of-range track, or no marker found on it — the drive instead hangs permanently, the same "fail by hanging, never by producing wrong output" behavior used throughout the GMA family.
 Because nothing downstream ever consumes the read data, a disk copy only

@@ Line 58: / Line 58: @@
 to pass — confirmed experimentally by corrupting the surrounding data on
 a real GMA85-derived disk and observing no change in behavior.
 == The drive-side program: annotated disassembly ==

← Older revision		Revision as of 00:43, 28 August 2026
Line 239:		Line 239:
	== See also ==		== See also ==

−	* [[GMA86]]
−	* [[GMA87]]
	* [[Robin of the Wood]]		* [[Robin of the Wood]]

@@ Line 178: / Line 178: @@
 </pre>
-This is a red herring, not a validation: <code>$02</code> is
+This is not a validation of anything disk-specific: <code>$02</code> is
 unconditionally set to <code>$97</code> by the shared "M-" command-channel
 opener every time it runs, regardless of anything measured on the disk -
 confirmed by reading that routine's own code, which contains a bare
-<code>LDA #$97 / STA $02</code> with no input dependency at all. The other
+<code>LDA #$97 / STA $02</code> with no input dependency at all. That
-four titles (Chimera, Willow Pattern, Booty, Cylu) skip this check
+doesn't make the check pointless, though: sitting where it does - buried
 entirely and simply discard the <code>JSR $C800</code> result, reaching
 the identical outcome by an even more direct route.

@@ Line 3: / Line 3: @@
 {{Special:Whatlinkshere/GMA85}}
-Notable [[Chimera/Willow Pattern]] uses $A3 as marker terminator instead of $A9.
+Notable [[Chimera / Willow Pattern (Firebird)]] uses $A3 as marker terminator instead of $A9.
 = Description =

← Older revision		Revision as of 00:21, 28 August 2026
Line 2:		Line 2:

	{{Special:Whatlinkshere/GMA85}}		{{Special:Whatlinkshere/GMA85}}
		+
		+	Notable [[Chimera/Willow Pattern]] uses $A3 as marker terminator instead of $A9.

	= Description =		= Description =

← Older revision		Revision as of 00:14, 28 August 2026
Line 1:		Line 1:
−	~~Descriptions needs to be done.~~
−
	==== Pages that refer to this protection ====		==== Pages that refer to this protection ====

	{{Special:Whatlinkshere/GMA85}}		{{Special:Whatlinkshere/GMA85}}
		+
		+	==== Description ====