Re: writing cdhdtape to CD

["Michael L. Hitch" <mhitch%lightning.msu.montana.edu@localhost>]

On Fri, 5 Jun 2009, Ray Phillips wrote:

> > A quick test would be to pad the cdhdtape image to a multiple of 18K, burn 
> > that adjusted image, and see if it works:
> >
> > dd if=cdhdtape of=/tmp/cdhdtape bs=18k conv=sync
>
> That was a promising idea Michael.  Executing that command produced a file 
> 3778560 bytes in size.  I burnt it to CD and tried to boot the PWS but the 
> "block size is not 512 bytes" error occurred and the boot failed the same as 
> usual.

  That sounds like the problem of your CD drive using 2048 byte blocks, 
and the SRM on the PWS probably has to have 512 byte blocks.

  I think the SRM on my CS20 can deal with the CD drive having 2048 byte 
blocks, and will do the buffering and addressing of 512 bytes when using 
the SRM read routine.  I just successfully booted my CD created as above 
on my CS20.

> % dd if=/dev/zero of=2048b bs=512 count=4
> 4+0 records in
> 4+0 records out
> 2048 bytes transferred in 0.001 secs (2048000 bytes/sec)
> % ls -l 2048b
> -rw-------  1 ray  wheel  2048 Jun  5 10:18 2048b
> % cat 2048b >> cdhdtape
> % ls -l cdhdtape
> -rw-------  1 ray  wheel  3778560 Jun  5 10:19 cdhdtape
> %
>
> but apparently that idea was way off track.  When I tried to boot the PWS 
> using it the screen went blank and the machine rebooted as though it had been 
> power-cycled.

  Hmm, that should have created the same image as my dd command - you 
could compare the two files to see if there was any difference.

> Fortunately I've been able to use CD-R/W media to minimize wastage. I've just 
> used a couple of CD-Rs to ensure that wasn't a factor.

  I'm not sure the CD drive in my CS20 would work with a CD-R/W.  I know 
the old DEC drives that came with the vax, decstatsion, and early alphas 
didn't seem capable of reading CD-R/W media.

> That's scary.  Do you think booting with cdhdtape has affected your alpha 
> somehow?

  No, the machine has been rather tempermental before.  After I upgraded 
to a 140GB drive on both my CS20 machines, it seems like they will boot up 
in some strange condition where the disk read speed is only 3-4 
Mbytes/sec, and seems to corrupt the data while reading it off the disk. 
I first noticed it when fsck found lots of problems with the file system. 
After several different attempts at booting using different kernels, I can 
finally get it in a state where the disk speed is normal and reading 
doesn't corrupt the data and it will run fine.  Then I tried running a 5.0 
kernel on both CS20 systems, and they seemed to run fine until one of them 
crashed.  After rebooting it, I had severe problems getting ntpd to sync 
and finally fingured out that the PCC source for the timecounter was 
getting configured with 1249660000 Hz instead of 833091856 Hz.  If I boot 
with an old 4.0 kernel, or the 5.0 GENERIC.MP [which does not work with > 
1 cpu currently], then my 5.0 GENERIC kernel gets the right frequency. 
Very weird.  And yet another problem is that the CD drive seems to get in 
a state where it won't read anything until I eject and reload it [I ran 
into that last night when trying to test my lastes cdhdtape image, and had 
to wait until I got into my office to eject the CD].

--
Michael L. Hitch                        mhitch%montana.edu@localhost
Computer Consultant
Information Technology Center
Montana State University        Bozeman, MT     USA