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B65 BASIC v0.2: 5-6x faster than BASIC 65, and 1000 moving objects

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@beniacm beniacm released this 09 Nov 15:52
· 47 commits to master since this release
v0.2
46cf09e

B65 BASIC is a BBC BASIC (Z80 v5 derived) interpreter for the MEGA65, rewritten for the 45GS02.

What's new since v0.1-dev.1

  • Speed: 5-6 times faster than BASIC 65 on the board. Per statement:

    statement BASIC 65 B65 v0.2
    POKE 135 µs 24 µs
    integer add and IF 142 µs about 24 µs
    4-byte ! write 162 µs 40 µs
    MOD/AND expression 328 µs 62 µs

    How:

    • a compiler for numeric expressions, assignments and single-line IFs, with a cache of the compiled code;
    • integer constants encoded when the line is entered, integer FOR...NEXT, and the 45GS02 math unit for *, DIV and MOD;
    • cached GOTO/GOSUB targets and PROC/FN definitions.

  • Moving objects (list mode v3, K325T step-6 core): B65 keeps the table for up to 1024 objects and moves them in its frame interrupt; BASIC only starts and steers them. The statements:

    • OBJECT, OBJVEL, OBJMOVE (straight, turning, exact polar), OBJORBIT, OBJSPRING;
    • OBJLIFE, OBJLIMITS / OBJBOUNDS (wrap, bounce, kill), OBJKILL, OBJUPDATE;
    • ON OBJEVENT, OBJX/OBJY/OBJVX/OBJVY/OBJEVENT( );
    • HITPIX(a,b[,dx,dy]), a pixel-exact overlap test.

  • The K325T collision engine: ON COLLISION PROCname and COLLIDE(n) for objects 0..1023.

  • Diagnostics: *INFO (version, machine, ROM, RAM, K325T feature level) and SELFTEST (one PASS/FAIL line per subsystem).

  • Other changes:

    • whole-array AND, plus a tight integer loop for whole-array + and -;
    • WAIT on the VIC-IV frame counter;
    • *DELETE keeps both FAT copies and the free count right;
    • the packed PRG starts in 0.78 s.

  • New examples: bounce (64 balls), swarm (255 objects), swarm2 (1000 bullets), jumper (pixel-accurate platforms) and selftest. The first line of every example says which core it needs.

On the K325T rig with the step-6 core, jumper, bounce and parallax run at 50 frames per second, and swarm2 at 49 with 1000 bullets.

Flag day: the step-6 core (mega65-core 0209a1c57) uses 32-byte object table entries. The object examples in this release need it, so do not run them on older K325T bitstreams (feature levels 1-2). Programs that build a 16-byte table by hand move entry n from base+16n to base+32n. Tokenised programs SAVEd by v0.2 do not run in v0.1-dev.1; keep text copies.

Downloads:

  • b65.d81: the interpreter as B65 plus the examples as text files. Mount it, then DLOAD "B65", RUN; in B65, LOAD "JUMPER", RUN.
  • b65.prg: the interpreter alone, load address $2001.

Verified:

  • K325T rig with the step-6 core: smoke 33/33, the v3 object board test 20/20, SELFTEST 14/14, and the demo timings above.
  • Xemu: smoke, check scripts, the object and HITPIX models, and the card tests (fsck clean).

A standard MEGA65 has not been tested yet. B65 is written to run on one: everything works there except drawing the list-mode objects, which still move logically. Nobody has tried it on a stock machine yet. If you have one, please type *INFO, run SELFTEST (LOAD "SELFTEST", RUN) and paste both into an issue at https://github.com/beniacm/b65-basic/issues. Reports of any kind are welcome.

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