Date   : Mon, 10 Jun 1985 16:02:50 EDT
From   : David Towson (SECAD) <towson@AMSAA.ARPA>
Subject: OMTI disk controller query - summary of replies.

Fellow CP/Mers and other Micronauts - A while ago, I posted to info-cpm and
info-micro a request for information on the OMTI 20C winchester disk controller
now being sold by the John Meshna surplus house for $150.  The response was
really super, and I'd like to thank all of you who provided information.  For
the benefit of anyone looking for a cheap mini-winchester controller, here is
a summary of the information I received:

     The OMTI controller is being offered for $150 by John Meshna in Lynn
Massachucetts, (617)595-2275.  They have had it in their catalog for quite
a while at $250, but they have just lowered the price.  I guess the boards
weren't moving.  Here is what the ad says:

     "The OMTI 20C board we offer is unused, late style surplus and will handle
two (2) 5-1/4" Winchester type drives.  Some features of the controllers are:
single +5VDC and +12VDC supplies, buffered slew/seek modes, overlapped seeks,
auto seek and verify, extensive fault detection, auto head and cylinder switch-
ing, full sector buffering 256/512 bytes/sector, 33 or 18 sectors/track (jumper
selectable), programmable disc parameters and much more.  Price is for the
controller card only ... does not include the disc drives or the host adapter
for your particular system.  We include data on using these boards with Seagate
ST506 disc drive in TRS model III & IV, plus a copy of the factory manual."


OMTI is very much in business and offers excellent SCSIbus controllers in their
5xxx series.  [We] were certainly pleased and pleasantly surprised at the
quality of their design (allows many parameters to be set by user thus accom-
modating field installation of unanticipated drives etc.) The 20C is an earlier
unit from the period when they were principally a second source for DTC
controllers.


Omti was purchased by Scientific Micro Systems (SMS), and they now make 
the 5{1,2,3,4}00 series which have 1-1 interleave & write pre-comp for the
floppy.  The original 20c (which I was using at my house for a few years),
works with winchesters fine, but does not have write pre-comp for floppies.
A new Omti 5300 is $269.


  I am responding to your message about the omti controllers.  You are
probably referring to the ones from Meshna.  I have one working one.   The
other is not known to work, yet.  The OMTI's are SASI and the manual that
you get will not have enough info on how to program them.  There is a 
well defined protocol that all OMTI controllers use.  I am told that the
protocol works on these controllers, and it seems to in the system that
we have.  The price of $150 each makes them very attractive.  There are
several things that you must be aware of, though.  These boards will not
support write precompensation at all.  Many drives work OK without it, though.
The controllers are "high performance" and are reputed to read a track in
two revolutions.  Presumably write one, also.  The one that we have works
well with a Maxtor drive (which needs no write precomp.)  If you are 
thinking of using a Maxtor, note that only the "little" drive (65 meg)
can be used.  The controller will not select enough heads for the bigger
ones.  It is a microcoded controller using a 2910.  It can address 8 heads.
By the way, Meshna was very prompt.  It took about a week to get the boards.
They do run very warm (due to the 2910 and proms,) though.


The OMTI controller you mentioned is used in an Alcyon 68K unix box which I
have had the pleasure to use for the past year and a half.  We have had no
problems at all with the controller or disks.  The controller has some special
features which can come in very handy:  

  Support for DMA 5/5 (5 M fixed, 5 M removable) disk drive

  fully programmable step rate selection

I am considering buying some to replace the western digital controllers
which hang occasionally.


A friend and I recently bought several surplus OMTI 20D's (same as the 20C
except for an added floppy controller chip).  We've been running them for >6
months now, and both of us have been quite satisfied with them, as far as they
go (they're a bit out-of-date by today's standards).  We've written drivers
for V7, BSD2.9, and RT11 with no problems (the SASI interface is very similar
to the better-known XEBEC controller).  They interface with 2 standard ST412
drives and a SASI host adapter, do 256 and 512-byte sectors, up to 2-to-1
interleave, automatic ECC check and correct, etc, etc.  They do bad-track
replacement in the usual way by marking an alternate track in the bad track's
headers - slow, but software-transparent.  The various drive-specific delay
parameters are all programmable, so it should work with almost any ST412-type
drive.  Also, the 20C's microcode supports some of the earlier cartridge wini
drives (IOMEGA Beta and DMA Systems 5/5) which have been showing up as surplus
lately.

OMTI still exists - they've been bought by SMS (Scientific Microsystems),
although they still use their old name as a trade name.  They now have a
newer, higher-performance line of controllers - check their ads in recent
issues of Electronics Week and other such journals.


     The bottom line (as they say in the parlance):  I ordered one.  Thanks
again to all who provided the above information.


Dave
towson@amsaa.arpa