🚀 go-pugleaf

Subject: low cost HARDDISK interface

In his article (9 Aug 88 15:07:47 GMT) icc!jlong@blackbird.afit.af.mil
  (Jeffrey K. Long) asked:
>Could someone please post more info on the article in the German magazine that
>told how to hook up a standard XT drive and controller to the ST!  Several
>people in my user's group are very interested in this prospect.  I understand
> that a circuit board and some driver software are all that is needed.  I also
>heard that with some patches the system could now autoboot also.  So what's the
>catch other than the fact that you don't have access to your DMA port?
>Is this thing slower than using a Berkley board and Adaptec controller?
>What magazine did it appear in (Name and Issue) and would anyone who reads
>German be willing to translate the article to English?  Help!!!!!

The low cost solution mentioned was published in the German magazine "c't"
(Verlag Heinz Heise GmbH & CoKG, D-3000 Hannover, W-Germany)
issue 2/88 p126ff . It uses an OMTI 55xx controller and a small interface
build up of 5 `standard' 74xx ICs. This solution occupies the whole DMA port -
so you have no further access to the DMA port. In issue 5/88 p122ff a ROM
patch was published which allows an autoboot.

Based on the idea of using an OMTI controller I developed another small
interface (9 `standard' 74xx ICs) which does not block the DMA port but
provides drivers for all important DMA port signals. It uses also the OMTI
controller 55xx and I have tested it with two controllers each supporting an
OMTI 5527a with 2 ST277R drives (240 MB in total !). But I haven't tested
the controller with Atari or foreign DMA port devices - in fact I don't
believe that it will work with the Atari laser printer (I have heard that
many other DMA port devices have difficulties with this printer or the
software). But I wanted to keep the port clean for further self build
hardware extentions and not for obscure foreign products.
The controller works with no problems since April 88 - the software (not
identical to that published in c't) consists of a GEMDOS driver,formatter &
utilities, an OS9 driver (real multitasking) & software to access GEMDOS
partitions from OS9 and vice versa. 8 partitions per Harddisk, 2 drives per
controller (up to 8 controllers,...) are supported. The speed is primarily
limited by the operating system (even with Fatspeed) - data transfer rate
with an OMTI 5527a : Interleave 1, 512 Bytes/sector, 26 sectors/track,
60 rpm = 800 kByte/s (There is no hardware to slow down the data transfer
rate !). My favorite solution consits of an OMTI 5527a and 1 or 2 ST277R
(each 65 MB), but I have also used an ST238R (32MB) and an ST251 (40 MB)
with an OMTI 5520a.
So the costs for a 60 MB harddisk are:
  selfbuild controller + cabels   c  50 DM
  OMTI 5527a                      c 170 DM
  Seagate ST277R                  c 850 DM
                                  ---------
                                 c 1070 DM c $580
  + Power supply

If there exits an real interest (several requests) I would try to explain
my own solution in detail and to post the sources (c200 k), but I won't
translate the c't solution (I don't know whether they would agree,...)

In a limited amount I would also be able to produce and send boards for
about 20 DM + postage. If there is a real great request I will perhaps
snake mail a copy of the layout (2 sided) to a few persons who oblige to
distribute this copy to all persons interested in it in their region.




Bitnet:  V61@DHDURZ1                               Ronald Lamprecht
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