fseipel@hpuxa.ircc.ohio-state.edu (Frank E. Seipel) (12/08/90)
This is another text file I had laying around.. If you'd like to see more,
please E-Mail me. I think this file is formatted to be output to a printer.
ATARI---->PC Conversion Page 1
THE FOLLOWING INFORMATION IS PRESENTED TO ASSIST THOSE INTERESTED IN
CREATING A CUSTOM ATARI COMPUTER SYSTEM IN AN IBM 'PC' CASE. IT IS BY
NO MEANS MEANT TO SERVE AS A COMPLETE DESCRIPTION OR 'HOW-TO-BOOK' ON
THE SUBJECT AND IT IS ASSUMED THAT THE PERSON WHO UNDERTAKES THIS
PROJECT IS WELL VERSED IN BUILDING ELECTRONIC PROJECTS. THIS
INFORMATION IS PRESENTED BY MICRO SOLUTIONS FOR USE IN THE PUBLIC
DOMAIN.
>>>SPECIAL NOTE:MICRO SOLUTIONS WILL NOT BE HELD RESPONSIBLE FOR
SPONTANEOUS MELTDOWN OF YOUR COMPUTER OR PERIPHERAL EQUIPMENT DUE TO
THE UNDERTAKING THIS PROJECT.
So you want to put you're ATARI into a 'PC' CASE....
Basically what's needed is: A thorough understanding of basic
electrical circuits, soldering skills, some mechanical ability, and of
course an IBM style case to your liking. These cases have become quite
popular and are offered in numerous configurations. The main thing to
remember when selecting one of these is, will your motherboard fit
inside it without TOO MUCH modification? (Let's try to keep the SKIL
saw in the closet for this project.) Another consideration, is whether
or not you wish to have a HardDrive as part of this All-In-One system.
Choosing an XL or XE computer makes this a much more viable
possibility, because of the parallel expansion buss and the various
HardDrive interfaces designed for this buss. Last, but not least, is
the very likely addition of a TransKey board to enable the use of an
external IBM style keyboard (well.... you know I had to say something
about my product in this article).
Most of these 'PC' computer cases on the market also come with a
fairly beefy switching power supply capable of running the Computer,
extra RAM, Disk Drives, and various hardware enhancements. To fully
take advantage of this built-in power supply requires some rewiring of
many of the stock Atari power plugs and devices. To minimize some of
this and to better utilize your storage media, it is recommended that
XF551 drives be used in this project. The nice thing about these
drives is the fact that they are really IBM type drive mechanisms in
disguise, this allows for a simple bolt-in, no modification
installation. The power connection on these drives will readly accept
the supplied power connectors on the switching supply and the drives
will give you 360K storage per disk with a suitable DOS (ie: MYDOS or
SPARTADOS). The XF controller (the PCB included with the XF551 drive)
will need some slight modifications as follows:
1) After seperating the two halfs of the original XF551 plastic
enclosure, unscrew the 4 screws holding the drive in place.
2) Unplug both the 34pin and 4pin connectors from the drive, then
lift it out of the enclosure and set it to the side.
3) You will now find a couple of screws holding the PCB to the
bottom of the enclosure. Remove these and lift the PCB straight up and
ATARI---->PC Conversion Page 2
out.
4) Desolder the 34pin header (w/cable) from the PCB and replace
it with an IDC style male header.
5) Clip off the 4pin female molex type power plug while leaving
the connection wiring intact. Now replace this with a male 4pin IBM
floppy power connector, being sure to matchup the PCB silkscreen
designations with the proper pin numbers (pin1=+12vdc pin2=GND
pin3=GND pin4=+5vdc).
6) Use a standard IBM drive cable to connect the drive to the
controller card. These cables normally have two edge card connectors
on one end, the END one is the one to use.
7) Now plug in power connectors from the switching power supply
to the Disk Drive and also to the controller. The drive is now ready
to use (be sure to set the drive select switches on the controller to
the desired SIO #).
If you wish to use a 3.5" drive(s) in your system and wish to
have them be capable of 720K storage, a complete kit and instructions
are available from Innovative Concepts. If you don't require the full
capacity, but would still like to use one of these smaller drives then
the following instructions are for you.
3.5" Drive Conversion:
Using the controller as first modified, connect a 3.5" IBM drive
in place of the 5.25" drive (this will usually require adapter plugs
that normally come with the drive when purchased). No further
modifications required.
Dual Media Drives from one Controller:
1) After performing the controller modifications already listed,
turn over the PCB and locate pins 10&16 on the 34pin header. You will
notice a trace connecting these pins together and another trace
leading towards the center of the board from pin16. Cut the trace
between pins 10&16 with an XACTO knife or razor blade, being sure to
leave the other trace on pin16 intact (this is the drive select line
from the floppy controller chip).
2) Solder a wire from pin16 to the center of a SPDT toggle
switch.
3) Solder a wire from pin10 to one side of the switch and solder
a wire from pin12 to the other side of this same switch.
4) Plug the other unused 34pin edge card connector on the floppy
drive cable into the 3.5" IBM drive (this may require an adapter).
ATARI---->PC Conversion Page 3
Also, plug in a power connector from the switching power supply (this
may require an adapter as well).
5) The SPDT toggle switch will now select which drive will
respond off of this controller (either the 5.25" or the 3.5").
Pin10=Drive 1 Select, Pin12=Drive 2 Select, 34pin edge card END
connector=Drive 1, middle connector=Drive 2.
With this setup you will be able to use either the 5.25" or 3.5"
drive with but one controller. Both drives will be capable of 360K of
storage. Only one drive is usable at any given time from the one
controller (Disk duplication and/or copying between the two drives is
not possible). A second controller and drive will still be needed for
disk duplication and/or copying.
Computer Power Connection:
For simplicity, a 600/800XL or XE are the computers of choice in
this situation. The reason; only a single +5vdc supply is needed,
where as the earlier 400/800 models and the 1200XL required either
9vac or if bypassed; +5vdc, +12vdc, -5vdc. The +5 and +12vdc is readly
available off of the IBM switching supply, but the -5vdc or 9vac
isn't. You could of course kludge up some sort of supply to handle
this, but in the long run, the XL/XE's are better for other reasons as
well (parallel buss & built-in BASIC to name a few).
The 600/800XL and XE's use the same power connection plug, this
is a 7pin DIN (an 8pin DIN can be subsituted by removing it's center
pin). On this plug pins 1,4,6=+5vdc and pins 2,3,5,7=GND. Either cut
off one of the provided power connectors on the switching power supply
and subsitute a DIN plug or better yet, make up a 4 pin male floppy
power pigtail with a DIN on the other end. Only +5vdc and GND are
required on this connection.
Hard Drive Installation:
To install a HardDrive with high speed access will require an XL
or XE computer having the External Parallel Buss (often times called
PBI or ECI). It is through this parallel buss that a special drive
controller will be connected, offering an industry standard HardDrive
interface referred to as SASI or SCSI. To the best of my knowledge
there are currently three such devices available, the CSS Black Box,
ICD's MIO, and Supra's Hard Disk Interface. Any of these is suitable
for putting a HardDrive in your system, merely requiring the
appropriate SASI or SCSI controller and drive.
If you're willing to sacrifice speed and if you can find it,
there is an SIO connectable device that will give you HardDrive
interfacing. It was called the ATR8000, actually a complete computer
on it's own, which used the Atari as a terminal link. With the right
ATARI---->PC Conversion Page 4
options, this Co-Processor board was capable of accessing HardDrives.
Even without extra options, the ATR8000 would allow for connection of
up to 4 IBM style Floppy disk drives, looking for the most part, as 4
Atari drives on the SIO port. It is also my understanding that higher
capacity drives were possible through special configuration, allowing
up to 1.2 MEG with the proper drive and DOS. There will be some
problems with this interface, such as not 100% compatibility with all
Boot Disks and/or DOS'es and very slow HardDrive access, otherwise it
is a good alternative for 400/800 users especially.
Some of the other advantages to the parallel buss devices, is
that they usually do more than just allow for HardDrive connection. To
name a few; extra expansion RAM usable as a RAMDISK, RAM for Print
Spooling, RS232 Port, Parallel Printer Port, and built-in Machine
Language Monitor. Not all features are offered or are all available
from any one device. The CSS Black Box is slated for a floppy drive
interface enhancement, possibly similar in nature to the ATR8000,s
floppy interface. This would give you an all in one drive controller
that's also fast.
Most of the parallel interfaces will require some relocation in
order to fit inside your 'PC' case. This amounts to fabrication of
ribbon cable extensions in some cases, which may be as simple as using
crimp-on connectors or as difficult as point-to-point wiring depending
on the interface and computer choosen. My actual experience was with a
Black Box and a 800XL computer. This was relatively simple, amounting
to building a cable from one 50pin edgecard connector, one 50pin
female IDC plug, and about 12" of ribbon cable. Both connectors were
of the crimp-on variety, making for a no solder installation. When
making your own cables, be sure to always line-up the pin#1's on both
sides.
With the flexability of the interconnecting ribbon cable, you
should be able to fit both the computer motherboard and the parallel
interface board into most any 'PC' case. A little imagination is most
useful in this task and good mechanical know how is imperative. Boards
can be stood on end or stacked, just depends on the particular
situation and alot on what you perfer to do. Find yourself a good
supplier of mechanical spacers, fasteners, and PCB guides, because
you'll be knee deep in them before your'e done with this project.
Power for your parallel interface can most likely be derived from
one of the floppy power connectors on your 'PC' switching power
supply. Once again it will require some rewiring of connectors and
some good electrical sense. Power for the HardDrive and it's
associated SASI/SCSI controller, will normally be as simple as
plugging straight into one or two of the leftover floppy power
connectors (by this time we may have exhausted all the available
connectors, have no fear there are 'Y' adapters available).
Now comes a problem, most HardDrives need a few seconds to rev-up
to full speed when first powered up. During this time they are not
accesable from the controller and many times this can result in bootup
ATARI---->PC Conversion Page 5
errors. One possible solution would be to provide a seperate power
switch on the front panel for the Atari computer, switching it on
after the HardDrive was up to speed. Another solution is something I
came up with on my system, a computer power delay timer. This
consisted of a 555 timer with it's trigger line tied to it's timing
capacitors positive side, a 5vdc SPST relay on the output of the 555
with the common of it's coil and switch going to +5vdc, and the entire
affair wired in series with the computer power line. Basically what
happens is, that upon power-up, the timer's output will immediately go
positive, thereby causing the relay to do absolutely nothing. After
the timer times out (depends on the RC network used), the output will
drop to GND causing power to flow through the relay's coil, pulling
the switch closed, and allow power to go to the computer.
555
pin #s
+5VDC---[:::]--2-6--+)(---GND
220 47uf
K
1--------GND
+5VDC----------4
" ----------8
*RELAY*
+5VDC--[COIL]--3
*RELAY*
*SWITCH*
+5VDC----o/o-----[ATARI]--GND
+5VDC----[<]---3
1N4004
The idea is to pick an RC network that gives sufficient time for
the HardDrive to rev-up, I found 220K for the timing resister and 47uf
for the timing capacitor to be quite good for my Seagate drive (this
gives about a 15 second delay). Increasing the resister's value will
result in a longer time delay and decreasing it, will produce a
shorter delay. It is also advisable to use a relay who's contacts are
rated for 1.5 amps, and for protection against arcing, solder a .01uf
capacitor across the contact connections. Also, to protect the 555
timer from high EMF voltages that may be generated by the relay's
coil, solder a 1N4004 diode across the coil with it's cathode (marked
with a line) going to the +5vdc side.
Another rather nifty feature of this power-up delay timer, is
that it offers an easy way to perform a ColdStart Reset for owners of
the TransKey board (there I go again). To do this, take the Gray wire
from the TransKey board, and instead of attaching it as suggested in
it's original instructions, solder it to pin2 of the 555 timer
instead. Now everytime you do a RESET from the IBM keyboard (attached
to TransKey), you will shutdown the power to the Atari computer for
ATARI---->PC Conversion Page 6
the duration of the time delay. This will of course result in a
ColdStart Reset, just as if you had reached around back and shut off
the computer's power switch and then turned it back on again. The main
advantage is that you don't need a special O.S. or software routine to
provide this keyboard coldstart reset.
Cartridge Port:
This is where things get alittle tricky....
How do you get access to the Cartridge Port once your Atari is
tucked inside the 'PC' case? Well the best solution I have seen, is
something that Bob Woolley from San Leandro Computer Club (SLCC) came
up with.
Essentially what he did was to take one of those 34pin IDC edge
card connectors (yes, the same one used for the IBM floppy drive
cables) and with a little filing on the ends, he was able to insert
this inside the plastic cartridge shrouding that came with the Atari
motherboard (that's right you have to remove it from the board first).
He then had a ribbon cable extending from this connector about 10-12
inches connecting to the Atari motherboard via a 34pin connector (this
required desoldering the original cartridge socket & replacing it with
wirewrap pins extending out the backside of the board). The completed
assembly was then meant to be mounted behind a 3.5" drive bezel for
insertion of the cartridge from the frontside of the 'PC' case. For
more complete information with pictures on this modification, consult
the May 1990 issue of the SLCC Journal. ***HINT: keep the ribbon as
short as possible for reliable cartridge operation***
Conclusion:
There are of course many other things that can be put inside your
new 'PC' case, but only you can decide what's best for you. Most
importantly, plan out this project carefully before you purchase your
'PC' case and be sure to leave yourself sufficient room for future
additions. (This will keep you from having to start all over again...
Yuck!) Most of all, have fun with your new ATARI PC and enjoy the
looks of approval you'll get from those unsuspecting IBM'ers out
there.
Sources for Items Mentioned:
BLACK BOX
Computer Software Services
P.O. Box 17660
Rochester,NY 14617
(716)586-5545
MULTI-IO (MIO)
ATARI---->PC Conversion Page 7
ICD
1220 Rock Street
Rockford,IL 61101
(815)968-2228
SUPRA HARDDRIVE INTERFACE
BEST Electronics
2021 The Alameda STE 290
San Jose, CA 95126
(408) 243-6950
XF35 KIT
Innovative Concepts
31172 Shawn Drive
Warren,MI 48093
(313) 293-0730
TRANSKEY (IBM keyboard interface)
Micro Solutions
P.O. Box 750396
Petaluma,CA 94975
Genie M.ST.PIERRE1