# Two diagnostic ISOs — the two-flash clue narrowed it down

Your report: **blue flash, boot menu, blue flash, reboot** — and the first blue
flash (before the menu) is NEW since I added the graphics mode to GRUB. That
first flash is just GRUB switching into an 800x600 graphics screen to draw its
menu; it's harmless. The failure is still: after you pick an entry, the kernel
takes over and the machine reboots almost instantly.

Because the C64 face is ALSO blue, I can't tell from "blue flash" alone whether
the kernel is drawing the C64 or whether that's just leftover GRUB-blue while
the kernel crashes. These two ISOs settle it.

## Boot ISO #1 FIRST:  1-TEXTMODE-diagnostic.iso

This one keeps GRUB in TEXT mode. The kernel writes the words **"HDGL BOOT OK"**
to legacy VGA text memory (address 0xB8000) as the very first thing it does —
which CANNOT fault on any x86 PC.

- If you see **"HDGL BOOT OK"** (white text on blue, top-left): the kernel IS
  running. The crash is then specifically in the graphics-framebuffer path, and
  I know exactly where to fix. Tell me: did it stay on that text, freeze, or
  reboot after showing it?
- If you see **NO text at all**, just reboot: the kernel dies before its first
  instruction — a multiboot/GDT-level problem — and I fix that instead.

Either answer is decisive. This is the one that matters most.

## Boot ISO #2:  2-GRAPHICS-with-markers.iso

Graphics mode with the four colored boot-stage squares (GREEN/CYAN/YELLOW/WHITE)
along the top-left, plus the corner fault-color-code. Boot it second.

- Which colored squares (if any) do you see before the reboot?
- Any solid corner color (red/magenta/yellow/green)?

## What to tell me (one line is enough)

"ISO1: [saw HDGL text / saw nothing], then [froze / rebooted].
 ISO2: [last square color I saw], [corner color if any]."

That single report tells me whether the kernel runs, how far it gets, and what
faults — and I fix the actual cause instead of guessing.
