[Simh] Disk sizing

[Johnny Billquist]

On 2017-02-06 01:11, Johnny Billquist wrote:
> On 2017-02-06 00:40, Mark Pizzolato wrote:
>> Now that Johnny pointed me to the ODS1 spec, I'm adding the
>> appropriate file
>> system structure definitions right now.   I have enough to solve this
>> case.
>
> Mark, I found a slightly revised ODS-1 spec that gives an alternative
> interpretation of the SCB block in BITMAP.SYS on ODS-1 for large disks.
> DEC did a revision.
> Putting that up as well, as http://mim.update.uu.se/ods1-1
>
> And the size limit mentioned is not correct. I seem to remember there is
> also a file level 403, and the limit of ODS-1 with 3+1 retrieval
> pointers are in fact 8G. I don't think that file level changes anything
> on how you find the disk size, though.

I'll try to find if I have any documentation for really large ODS-1 
volumes. But for now, I can report this:

They seem to still use 402 of H.VLEV
In the SCB of BITMAP.SYS, all four initial bytes (number of storage 
bitmap blocks) are 0. And then comes disk size. And then the number of 
blocks for the bitmaps comes after the disk size instead.

I can provide example dumps of the SCB if you need any.

	Johnny

-- 
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