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I'm recovering data from old QIC backup tapes for an acquaintance, which I do by dumping the raw data in Linux, and decoding the files from it using my own scripts, which handle several standard backup formats.

These tapes, however, seem to be using a format I haven't seen before. It begins with a 512-byte header that just contains the following:

00000000  3F 54 58 56 65 72 2D 34 35 00 00 00 00 00 00 00  ?TXVer-45.......
00000010  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000020  2E 00 00 00 00 00 00 00 00 00 00 10 00 00 00 00  ................
00000030  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000040  00 00 94 81 45 B4 4E 45 43 20 4C 61 70 74 6F 70  ..”.E´NEC Laptop
00000050  20 53 79 73 74 65 6D 2C 20 6D 79 00 00 00 00 00   System, my.....
00000060  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000070  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000080  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000090  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000000A0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000000B0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000000C0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000000D0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000000E0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000000F0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000100  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000110  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000120  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000130  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000140  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000150  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000160  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000170  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000180  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
00000190  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000001A0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000001B0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000001C0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000001D0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000001E0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
000001F0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 8A A4  ..............Š¤

Pretty much the only metadata we get is a volume label, a checksum at the end of the sector, and a mysterious magic header ?TXVer-45. Does anyone have an idea what software might have written this backup?

This would be useful to know because the file contents that follow this header seem to be compressed, and knowing which software wrote the backup would be a hint about what compression scheme it's using.

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    Do you have an approximate age for these tapes? Knowing the age sometimes gives a good hint as to the compression format.
    – Mark
    Feb 2 at 4:31
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    @Mark The tapes are from around 1994, and they are QIC-150 tapes, implying that they were written with an early SCSI tape drive. (And needless to say, the original user doesn't recall what software was used.) I posted a question on Reverse Engineering SE about decoding the actual compression format, which seems to be a derivative of LZ77, but annoyingly dissimilar: reverseengineering.stackexchange.com/questions/31478/… Feb 2 at 15:31

1 Answer 1

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I ended up figuring out that this backup was made using an extremely obscure tool called TXPLUS, which was a proprietary backup utility shipped with TapeXchange tape drives, which were tape drives in a custom enclosure that connected over the parallel port.

The only mention of TXPLUS on the web is a clipping from a 1993 issue of InfoWorld magazine. Fortunately I was able to extract the TXPLUS tool itself from this tape backup after reverse-engineering the backup format.

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