[Info-vax] VAX 6000 on Young Sheldon

[Johnny Billquist]

On 2023-02-12 01:28, Arne Vajhøj wrote:
> On 2/11/2023 7:02 PM, Johnny Billquist wrote:
>> On 2023-02-11 17:26, Arne Vajhøj wrote:
>>> On 2/11/2023 11:18 AM, Tony Priborsky wrote:
>>>> I'm pretty sure it didn't write a native VMS backup saveset -
>>>> remember the CPU on the HSC was a PDP-11.   Logically the backup was
>>>> the equivalent of VMS "BACKUP/PHYSICAL".  I seem to recall that at
>>>> some point the VMS backup could restore (read) a HSC backup.
>>>
>>> So no CRC and no redundancy groups?
>>
>> Depends on how you mean that. Tapes have CRC on the data unless I 
>> remember wrong. Just like disks have.
> 
> As I remember 9 track tapes then it was pure data blocks
> and tape marks - no CRC.

On a software level, you don't see this anymore than you see all the 
extra cruft on a disk.

> If mounted as labeled tape then some blocks were
> considered VOL and HDR blocks, but that was an OS
> feature not a drive feature.

Correct. From a hardware point of view, those are just blocks just like 
anything else. No difference at all.

However, the tape have blocks. You have the tape marks, blocking and 
other stuff going on, to try to ensure your data is safe and don't get 
corrupted. It's all down in the hardware, but that don't mean it work 
any worse/different.

   Johnny