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Main Street Publishing.
Re-release of Tumble Bugs.
Two files included.
"A" is the unmodified / original disk and does not load through. Actually, either due to a bug or an error during the duplication process, it appears no working original ever surfaced! For preservation purposes, we are keeping this VAPI image in the archive.
"B" is a fully functional, fixed version by Fandal with just a single byte to the code changed. Presumably, the original should have looked like this.
Below is Fandal's explanation...
"If your ATX image is a copy of an original disk, there never was any chance it could boot. There is a bug in the code.
I'm attaching a fixed version of ATX image. I changed just one byte as I noticed that there is a lot of bad sectors on original ATX starting at sector $265. Please note that loader checks sector $16D using this construction in the code:
18BE LDA #$6D ; LO byte of sector
18C0 STA $030A ;DAUX1 -> SIO table
18C3 LDA #$01 ; HI byte of sector
18C5 STA $030B ;DAUX2 -> SIO table
18C8 JSR $E453 ;DSKINV -> read sector
18CB LDA $0303 ;DSTATS -> read error flag
So I said to myself: may be it should check sector $26D instead of $16D? I changed LDA #$01 to LDA #$02 and voila! It works now.
I'm not sure if it is a programming bug or the master disk of Magneto Bugs
was damaged somehow but I would say that this mystery is solved".