z486 XL 20260906 — experimental KV260 release

z486 XL brings the z486 DOS PC core and experimental Voodoo 1-compatible
zSST acceleration to the AMD/Xilinx Kria KV260.
It is for people who already own a KV260 and is separate from z486_MiSTer; it
does not run on MiSTer.

The PC runs at 100 MHz with a 512KB write-back L2 cache in UltraRAM, VGA output,
VHD disk support, Sound Blaster 16 audio, and USB keyboard and mouse input. It
ships as a bootable microSD image with a minimal Linux command line; use
z486-run to launch a VHD. Board testing covers Doom, Quake 1.0.6 (not
GLQuake), and other DOS software.

All you need is a KV260, microSD card, HDMI display, and USB keyboard and mouse.
No external SDRAM module or FPGA add-on board is needed.

Performance

These board measurements compare z486 XL at 100 MHz with the regular
z486_MiSTer 20260831 release on the DE10-Nano at 85 MHz.

Benchmark	z486 XL KV260	z486 MiSTer DE10-Nano	Platform uplift
3DBench	65.1	53.1	22.6%
Doom, maximum detail	38.5 FPS	31.3 FPS	23.0%
Quake 1.06	8.1 FPS	6.8 FPS	19.1%

The L2 cache offsets the KV260 DDR's higher access latency; without it, this
design benchmarks below the DE10-Nano despite running at 100 MHz.

zSST Voodoo 1 implementation

zSST is a new SystemVerilog implementation of the 3dfx Voodoo Graphics chipset
by nand2mario. A direct reproduction of the original architecture would be a
poor fit for a modern FPGA board. The KV260's four DDR chips provide much more
bandwidth than the original eight EDO DRAM chips, but also have higher latency.
To suit this memory system, zSST schedules memory traffic and the rasterization
pipeline differently.

The implementation works but is still early. Tomb Raider is the only 3dfx game
tested so far and currently runs at about 12 FPS in Level 2. The
microarchitecture has substantial optimization headroom, and zSST is open
source.

Installation

Download z486_XL-sd-kv260-20260906.wic.xz, write it directly to a microSD
card with Balena Etcher, and boot the KV260 from that card.

Log in as root with password 1, then use passwd to secure the board.

The image includes boot0.rom and boot1.rom. Copy VHDs to /root/games over
SFTP/SCP, or plug in a USB drive; USB filesystems appear under /media. For
example:

z486-run /media/<usb_drive>/game.vhd

Use z486-run --help for RAM and audio-gain options.

Discussion and feedback

Use the z486 XL for Xilinx KV260 discussion
category
on GitHub for setup questions, test results, compatibility reports, and
development.

Download verification

SHA-256 for z486_XL-sd-kv260-20260906.wic.xz:

c7c5ad80b8b0f2ff283b54e412f04e87439ef73fa9ddd5560205f84fa246e6d7