Suggestions for VT103?

Jerome H. Fine jhfinedp3k at compsys.to
Sun Dec 28 20:38:02 CST 2008


 >Josh Dersch wrote:

> I have a number of RQDX3's, but I'll probably go with the Emulex QD21 
> ESDI controller that I have.  It has an auto-boot option, which will 
> be useful since the 11/23 board I have just has the ODT ROMs...

Jerome Fine replies:

I use a Sigma RQD11-EC quad ESDI controller which can run 4 ESDI drives.
What I like best is that 3 drives are VERY easily (just ground the 
correct line)
made WRITE  PROTECTED.  Not having a proper panel, I just use a 10 pin
cable and alligator clips to ground the line.

The Hitachi DK515 with about 600 MBytes each work well.  I modified the
RT-11 MSCP device driver to allow me to boot any of the 60 partitions on the
3 drives.  Normally, I use 3 drives with 2 being backups and only drive 
0 with
20 RT-11 partitions being modified at any time.  All drives are usually 
WRITE
PROTECTED most of the time since I normally fix bugs in the RT-11 operating
system and the device drivers.  Since any mistakes in my code modifications
could corrupt the hard drive, having them hardware WRITE  PROTECTED
prevents that until I have checked out the code.  After I have made the 
changes
to the backup drives, I boot the backup drive and copy the changes to 
drive 0
which is now just a data drive.

I have 2 command files which compare all 20 partitions on drive 0 to each of
the 20 partitions on drive 1 or drive 2.  That takes about 4 minutes for 
each
pair of RT-11 partitions of 32 MBytes each or about 80 minutes in total.

Under Ersatz-11 with a core 2 duo, it takes about 1.7 seconds per pair of
RT-11 partitions of 32 MBytes or about 30 seconds for all 20 pair of RT-11
partitions - not even time to get a drink.  I am working on enhancing 
the HD:
device driver under Ersatz-11.  It is twice as fast as the MSCP device 
driver.

For raw throughput, if I bypass the HD: device driver code and use a user
subroutine without interrupts (hardly necessary when things are this fast),
making a copy of an RT-11 partition of 32 MBytes is twice as fast again.
A straight copy is about 0.2 seconds for all 32 MBytes as opposed to
about 240 seconds the copy an RT-11 partition on those very fast (for
a real DEC PDP-11/83 system) ESDI hard drives.

Sincerely yours,

Jerome Fine



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