Speeding up Wren-V bandwidth

[Dirk Grunwald]

We just finished turning on the cache enable bit on a CDC Wren V
hooked up to a DECstation-3100. This speeds the bandwidth from
~350->400 Kb/s to about 1000 Kb/s.

To do this,

(1) make certain your disk lot number is 8920 or greater.

(2) hook your disk up to a Sun (I hope DEC is embarrased by this) and
reformat the drive using the disk name "CDC Wren V 94181-702". The
entry should look like:

disk_type = "CDC Wren V 94181-702" \
        : ctlr = MD21 : fmt_time = 4 \
        : cache = 0x11 : trks_zone = 15 : asect = 2 \
        : ncyl = 1543 : acyl = 2 : pcyl = 1545 : nhead = 15 : nsect = 48 \
        : rpm = 3592 : bpt = 33408

Note that this is the correct geometry. Earlier, someone had told me it
was ncyl = 1505 , nhead=15, nsect=52 which is wrong.

(3) Then, hook it back up to your DECstation, newfs everything again,
restore your disk and give it a whirl.


we ran /usr/field/dskx on it for about 5-10 minutes with no errors.

Even if you own a sun and bought a Wren V but didn't format it, this
might be a useful thing to do. Check out your bandwidth with 'dd' and
see if it's less than 750 - if it is, reformat the drive using sun 'format'.

Dirk Grunwald -- Univ. of Colorado at Boulder	(grunwald at foobar.colorado.edu)
						(grunwald at boulder.colorado.edu)