Graffity [Zorro II]/[Zorro III] model

Ateo Concepts’ Graffity boards reuse the same CL-GD5428 core as Picasso II+ (CirrusGd5426::new_gd5428), so their register, VRAM, and BitBLT behaviour is identical to that model. What differs is the autoconfig identity and window layout -- Graffity has its own registered manufacturer ID (2092) and wires the switch-strobe and VGA-register ranges differently from Picasso II. See Writing Zorro board plugins for the autoconfig chain and The video pipeline for presentation.

Zorro II layout¶

Like Picasso II, the physical board exposes two chained Zorro II identities: a linear VRAM aperture (product 34, window 1) and a register aperture (product 33, window 0). Graffity’s register aperture is 128 KB rather than Picasso II’s 64 KB, though only the low VGA port range within it is live.

Unlike Picasso II, Graffity’s register window addresses VGA ports directly at the window offset (no odd/even port-mirroring quirk): offset $3B0-$3DF reaches the corresponding VGA port 1:1. Any write with offset bit 15 set ($8000+) is a monitor-switch strobe decoded from address bits 6:5: 11 (+$60) shows the RTG screen, 10 (+$40) restores the native Amiga display, and other patterns are ignored. This is a different encoding from Picasso II, which decodes the switch from address bit 12 of an even-address write.

Zorro III layout¶

The Zorro III board is a single 16 MB autoconfig window (product 33, no window tag) with three fixed sub-apertures:

• +$400000, 64 KB: pure monitor-switch strobe trap. Writes here never reach the VGA core; only the $60/$40 address pattern toggles the switch.

• +$800000, 64 KB: the real VGA-register window, same direct port addressing as the Zorro II variant.

• +$C00000: linear VRAM, sized to the configured 1 or 2 MB.

Everything else in the window reads as open bus and ignores writes.

INT2 wiring¶

Graffity has no board-level interrupt-enable latch of its own (unlike Picasso II+'s register-window $1000/$1001 gate). INT2 follows the CL-GD5428 core’s own vertical-blank state directly (CirrusGd5426::vblank_pending), which latches only when the guest has enabled the vertical interrupt through VGA CRTC $11; writing CRTC $11 with bit 4 clear acknowledges it.

Presentation and diagnostics¶

As on Picasso II, the board presents its own frame only while the monitor switch selects RTG and the programmed mode is valid. COPPERLINE_DIAG_PICASSO=1 enables the same diagnostic logging as on Picasso II, including monitor-switch changes.

Reference¶

Board-level facts (autoconfig IDs, window layout, no-ROM autoconfig synthesis) were taken from amiberry’s src/gfxboard.cpp GFXBOARD_ID_GRAFFITY_Z2/ GFXBOARD_ID_GRAFFITY_Z3 board table entries and their init_board/ special_pcem_get/special_pcem_put handlers, cross-checked against the classic Aminet Picasso96Install package, which ships Graffity.card as a first-class Picasso96 board driver. The chip register model itself is unchanged from Picasso II/II+.