[HECnet] installing LPs on RSX

[Johnny Billquist]

On 2015-04-28 01:41, Lee Gleason wrote:
>     It doesn't take much of a program/script to strip off headers and
> trailers, or add them if required. I've had to do it when service
> bureaus didn't follow my instructions when I've had them read old tapes
> onto files.
>
>   What does a dump of the first block look like?

Lee, the tapes are corrupted in a much more sophisticated way.

All tape blocks are there. However, occasionally, they have been reordered.
Assume you have all tape blocks numbered consecutively, including tape 
marks, which looks like zero length blocks.

In a corrupted tape, you might then see the blocks in the following order:

1,2,4,5,6,3,7,8,9,...

When a reordering happens, the number of blocks later the "correct" 
block appears seems to be anywhere from 1 to 4 blocks ahead. I have not 
been able to spot any patterns to when a block reordering have happened, 
and I have not been able to spot any pattern to how many blocks later 
the reordered block appears.

My only guess is that when Tim Shoppa did the original dumps he used a 
program that read multiple blocks in one operation. When a read error 
occurred, the program noted, and went back and re-read the bad block. 
However, the original read read multiple blocks and the ones following 
the read error still got read, and put in the buffer, causing the 
reorder to happen. But that is just my guess.

	Johnny


>
>
>
> --
> Lee K. Gleason N5ZMR
> Control-G Consultants
> lee.gleason at comcast.net
>
> -----Original Message----- From: Dave McGuire
> Sent: Monday, April 27, 2015 5:22 PM
> To: hecnet at Update.UU.SE
> Subject: Re: [HECnet] installing LPs on RSX
>
> On 04/27/2015 06:04 PM, Johnny Billquist wrote:
>>>    Uh-oh...That "HDR1" business looks like part of an ANSI tape label,
>>> not a filename.  What do you think?
>>
>> Definitely a corrupted tape.
>
>   Yup...After testing several other images from the trailing-edge
> archive, I'm finding the same sort of mess.  I knew the BP2 v2.7 image
> was trashed, but it looks like quite a few others are as well.  The
> f77_v5_4.tpc one is corrupt too.
>
>   What a mess.
>
>   Thanks for your help in diagnosing this.
>
>   At least some earlier releases are intact, but do you know if any of
> those newer ones have been archived intact anywhere?  Do you have them?
>
>                -Dave
>


-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol