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Notes on w11 systems: w11a for Basys 3


The sys_w11a_b3 system is a w11a implementation for the Digilent Basys 3 board. The w11 memory is based on BRAMs only because the board doesn't feature any memory outside the FPGA.

For complete configuration, see sys_conf.vhd. The most important features are:

Property Value
CPU options FPP: no; Cache: 8 kB
Memory 176 kB from BRAMs via pdp11_bram_memctl
Devices DL11:2; DZ11, PC11, LP11, DEUNA, RK11, RL11, RHRP, TM11, IIST, KW11P, M9312: yes
Diagnostics rbmon: no; ibmon: no; dmpcnt: yes; dmhbpt: 2; dmcmon: no
Rlink 12 Mbps via FT2232HQ based serial link


The board has 16 LEDs and allows a nice console light emulation. The memory size of 176 kB allows starting a few oskits. u5ed works fine. XXDP, RT11 and RSX-11M should work. 211bsd will not boot, neither most RSX-11M+ systems.

For complete instructions on how to run operating system images, see w11a_os_guide. The default setup is:

  SWI = 00000000 00101000   (gives console light display on LEDS)
  ti_w11 -tuD,12M,break,xon  @<oskit-name>_boot.tcl

Status & History

The Basys 3 board is one of the w11 development platforms. The sys_w11a_b3 design is regularly FPGA tested with ostest against the oskits running with 176 kB memory.

  • 2015-02-08: initial version.