[Simh] TOPS-20 4.1 BUGHLT

[Timothe Litt]

On 11-May-15 13:33, Cory Smelosky wrote:

> I repeated the install, fresh structures, repeated TSU install.  No
> issues this time.
>
Glad you succeeded.
>
> Sounds like just a corrupted disk.
>
That really shouldn't happen, barring a crash of the host hardware, or
an unclean shutdown of the OS.  Don't do that.
>
>> Disk space is now so cheap that the easiest way to backup these
>> systems is
>> to simply copy the SIMH disk images (with the simulator stopped after a
>> clean
>> OS shutdown.)  That's my recommendation for all SimH machines...
>> These disks
>> are smaller than your typical video (or a couple of hundred photos).
>>
>
> How well do they compress?
>
Depends on data.  Try it and see.
Since 36 bits are stored in 64, there's an automatic inflation of 1.8x
of zeros.

After that, depends on your data & the compression.  Since most text files
aren't byte-aligned (7-bit bytes), you should use/set your compressor to
allow fairly wide codes (if it's variable width). 

For common sofware: on a random disk, I've seen  7-zip compress a fairly
full
disk to 15%, zip to 30% (that's compressed size/input size, so smaller
is better.) 

But it really doesn't matter.  The capacity of an RP06 is ~177MB;
notebook PCs
these days come with 500GB-2TB drives.  So you can fit 2,800 RP06s on the
 'small' drive; 11,000 on the large ones.  OK, divide by 1.8 for 1,500
/6,300.
Desktops, network storage tend to be bigger.  So a few backup copies of
your
RP06s really isn't a big deal, even uncompressed. 

YMWV.


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