VMS5: Fatal disk error when mounting 4.5GB hard disk

[Brian Tillman]

>Why do all these disks work under VMS6 but
>only some under VMS5? I have seen various
>articles suggesting an 8.5GB limit, but
>this does not explain why the 4.5GB disks
>fail.

There were considerable device driver changes between V5.5 and V6 that would account for them working on the later version but not on the former.

[Stanley F Quayle]

> We have applications which use PSI and X25. I understand this has changed significantly under VMS6. We would probably need to modify and recompile a lot of Fortran and PERL apps. Initially I thought it would be easier to get the 4.5GB disk to work.

Yes, I've seen cases where "upgrading" breaks things. Support of X25 is a little spotty, at least in the US. Last time I spoke with HP (at the time, Compaq, about 2-3 years ago), I got the distinct impression that no one in the US knew anything about X.25.

The good news is that you can move to another VAX and keep 5.5-2. The version that CHARON-VAX supports requires 5.5-2H4, but that's a minor upgrade. No X25 stack changes are required, as I recall.