19 Sep
2023
19 Sep
'23
6:02 a.m.
Any suggestions as to why the on-the-fly algorithm did
not catch on more in the 1980’s? Maybe it was simply less well known than I think?
The CRC algorithm I'm familiar with shows up in Dragon Quest for the Famicom in
1986[1], written in 6502 assembly. Admittedly though I only recognized it due to the EOR
with 0x1021 on lines 318-323. That I then only know from a quick and dirty CRC I threw in
an XMODEM-CRC client [2] I did to accommodate for a bug in the JH7100 RISC-V board's
recovery ROM implementation. Not sure if this is along the lines of the approach
you're talking about, admittedly these two instances are literally all I know about
CRC, just enough to be dangerous :)
Still, a concrete example of ChunSoft's 6502 CRC calculation in the mid 80s, if that
helps with the assessment of the time period/flow of ideas in the industry.
- Matt G.
[1] - https://gitlab.com/segaloco/dq1disasm/-/blob/master/src/chr3/start_pw.s
[2] - https://gitlab.com/segaloco/riscv-bits/-/blob/master/util/sxj.c