PDP-11 disk image question

[Charles Anthony]

On Mon, Feb 18, 2019 at 2:24 PM Bill Gunshannon via cctalk <
cctalk at classiccmp.org> wrote:

> On 2/18/19 4:35 PM, Paul Koning wrote:
>
> > It would be interesting if you can post the exact sizes in blocks of the
> SIMH image, and the real disk you copied it to.  That would help confirm my
> guess that it's a size issue.
>
> If it's a size issue then one of them is doing it wrong because the
> size of an RA81 constant.
>
>
Looking at the SIMH code:

/*
    type sec     surf    cyl     tpg     gpc     RCT     LBNs
    RA81 51(+1)  14      1258    14      1       2856    891072
*/

#define RA81_SECT       51                              /* +1 spare/track */
#define RA81_SURF       14
#define RA81_CYL        1258                            /* 0-1247 user */
#define RA81_TPG        RA81_SURF
#define RA81_GPC        1
#define RA81_XBN        2436                            /* cyl 1252-1254? */
#define RA81_DBN        2436                            /* cyl 1255-1256? */
#define RA81_LBN        891072                          /* 51*14*1248 */
#define RA81_RCTS       2856                            /* cyl 1248-1251? */
#define RA81_RCTC       1
#define RA81_RBN        17472                           /* 1 *14*1248 */

I am presuming that (without actually checking) that these are the numbers
returned to RSTS when it queries the disk; if these numbers are different
then the h/w, then that could be an issue. I am a bit curious about "+1
spare/track" - I wonder if the h/w reports 51 or 52?

-- Charles