[Info-vax] Exploring a hard drive on a new Vaxstation

[Johnny Billquist]

On 2018-02-01 09:42, Eberhard Heuser wrote:
> Am 01.02.2018 um 00:38 schrieb Steven Schweda via Info-vax:
>>> [...] Considered booting the 3100 over DECnet from my SIMH
>>> installation [...]
>>     A pedant might say that that's not actually DECnet, but
>> don't worry much about it.
>>
>>> [...] my SCSI CDROM [...]
>>     Not a very detailed description.  If it has a block-size
>> jumper, then you might need to set it to 512.  The right
>> cable is the real challenge.
>>
>>> My issue now is Windows (10, XP) doesn't see the VMS Iso as a
>>> proper file for burning so I'm planning a Linux setup just to
>>> burn the CD.
>>     Probably because it's an ODS2 image, not an ISO-9660
>> image.  I seldom need one, so I know nothing, but I'm
>> confident that there are (free) third-party programs out
>> there which run on Windows and don't care.  (Or get a Mac.)
>>
>>> Once I get the 3100 booted I'll check out the hard drive
>>> but I just imagine it'll need a fresh install.
>>     Plausible.  But an RZ23 is pretty tiny for VMS.  As I
>> recall, when I bought my VAXsta 3100 collection, most of the
>> RZ23 and RZ24 disks went into old Macs, where they looked
>> big.  I haven't tried shopping for a nice Seagate SCSI 1GB
>> disk lately, but I'd guess that they're either very cheap
>> (and/or dead) or very expensive.  ST11200N?
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> 
> It is possible to use a bigger SCSI-drive (used 4GB drives are still 
> available).
> I've modified a linux source code that modifies an entry in the drive
> in order to identify as a drive with a smaller capacity. So,  if you are 
> running a linux
> system with SCSI controller you are able to handle this problem.

??? There is absolutely no need. There is nothing that checks or 
complains if you use a larger disk. It's only a problem that the boot 
rom driver cannot access data on blocks beyond the 1G limit. Once the OS 
is up and running, that driver in rom isn't used anyway, and there is no 
limit at all. And if you can make sure that during the initial stages of 
the booting, no access is needed to a block beyond the 1G limit, then 
any disk works just fine.

It's not the actual capacity, or even the announced capacity that is the 
problem. It's just a simple case of the addressing of block numbers by 
the driver in the rom of those VS3100 machines just use a 21 bit value 
for the block number. Hence the 1G limit. So it's all just about the 
actual blocks accessed. If you use Linux, just have a first partition on 
the disk that isn't more than 1G, from which you boot, and the rest of 
the disk is a second partition, and everything will always work just fine.

   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