On May 20, 2014, at 8:33 AM, Cory Smelosky <b4 at gewt.net> wrote: So: Pack cluster size is not 1, 2, 4, 8, 16, 32 or 64. PC=120324 PS=030344 OV=000006 M5=004000 M6=004200 SP=041240 R0=000026 R1=143161 R2=143161 R3=000000 R4=000000 R5=041350 The disk should be around ~512M. I created a 500M disk. Disk? DU0 Pack ID? 0 Pack cluster size <16>? MFD cluster size <16>? SATT.SYS base <30530>? Pre-extend directories <NO>? PUB, PRI, or SYS <SYS>? [1,1] cluster size <16>? [1,2] cluster size <16>? [1,1] and [1,2] account base <30530>? Date last modified <YES>? New files first <NO>? Read-only <NO>? Patterns <3>? 0 Erase Disk <YES>? YES Proceed (Y or N)? Y Unless the partitioning is written to the first block and not done through controller NVRAM...I can't see the reasoning. Could you explain what you wanted to do, what steps you followed, and what exactly the trouble is? If you feed a disk to RSTS that doesn t have a RSTS file system on it, it will get confused/annoyed. The error message you quoted is an example of what you would see. Given an uninitialized disk, you use the disk initialization procedure (from INIT or online). The dialog you showed does that. After that procedure, you ll have a RSTS format disk. Partitioning? RSTS doesn t have partitions. The whole physical drive is a single file system. It also doesn t depend on NVRAM (PDP11s traditionally have none). Block 0 is the boot block (dummy not bootable boot block by default). Boot 1 is the superblock ( pack label ). For new (V9 or later) disks that points to the MFD (top level directory); for old disks (format 0.0) it is the first block of the [1,1] directory which doubles as MFD on that layout. paul