PC Historian Finds Puzzling Game Diskette Image

This past weekend, Trixter — a self-proclaimed IBM PC historian — picked up some old software for his archive. What he didn't count on was a couple of additional Avantage titles that had never been released into the wild. If this weren't enough of a find, one of these titles provided Trixter with an interesting puzzle: the diskette for Mental Blocks is apparently hand-formatted to work on both C64 and IBM (on a single side, not the "flippy disks" of old). Quite an interesting little piece of history.

Comments

Re:Hybrid disks - not a novel idea after all!

[Hatta]

Do those disks really use multiple formats, or do they just have Mac and PC binaries available on the same standard ISO file system?

The cool thing here is the media format itself is a hybrid. C64 disks in general are incompatible with DOS disks. But some clever hacker out there figured out a way to build a file system that's valid for both machines. A better analogy would be formatting a disk so that it's ext3 and NTFS *at the same time*.

Re:Hybrid disks - not a novel idea after all!

[banzaikai]

{Sigh}

Okay, folks, here's how you do it...

1) Format using 1541. This will put 174K of data on the bottom side of a DSDD floppy.
2) Manually edit the Block Allocation Map (BAM) to map out ALL tracks/sectors between 0 and 17, leaving track 18 (the BAM) and 19-35 for the 64 program and data (I figure about 82K will be free).
3) Write 64 stuff to disk.
4) Pop disk into PC drive, and either use a custom utility, or just use the FORMAT command specifying that only tracks out to 17 be formatted (FORMAT A: /T:17 /N:9). This allows BOTH sides of the disk to be formatted up to track 17, giving you about 180K to play with. Given the lousy graphics on PCs at the time, this is all you really need. This WILL NOT overwrite any 1541 formatting, since the BAM sits at track 18, and the FAT sits at track 0.
5) write PC stuff to disk.
6) PROFIT!

Another person above wondered if the 1541 had an auto-remap of bad sectors... NOPE. A bad disk/sector would trigger the "headbanger" routine, and the format would fail. In fact, the reason the 1541 was so slow at formatting (about 2 minutes for 174K) was that it would write the track, then read it back to verify, update the BAM, then go back to do the next track. Fastload cartridges bypassed the verify and BAM routines, and could do the same thing in under 30 seconds.

Seriously, am I the only one here who read "Inside 1541 DOS" by Immers and Neufeld?

banzai "Bam-Bam" kai