Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!YODA.EECS.WSU.EDU!gheller
From: gheller@YODA.EECS.WSU.EDU (Geoffrey Heller - CS216)
Newsgroups: comp.sys.amiga.hardware
Subject: 2320 on an A500 and external drive port hardware interfacing
Message-ID: <9012120327.AA16486@yoda.eecs.wsu.edu>
Date: 12 Dec 90 03:27:24 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 39

Hello C= and other hardware hackers out there!  Here are a few questions
which have been puzzling me for some time...

Question #1:
  I have an A500 with Trumpcard 500 on it.  I am very interested in the
2320 graphics board but I'm told it is only available for the A2000.  Now,
I do have a bit of experience at hardware hacking and I would like to know
if it would be easy to add a 2320 onto my A500 bus.  If not, would anyone
care to recommend a solution to the flicker problem on A500's?  I hear that
IDC has a $400 board for the A500 that solves the flicker problems, does
anyone know about how well it works?

Question #2:
  I am currently working on a device which will utilize the Amiga external
3.5" disk port.  In the AMIGA HARDWARE REFERENCE MANUAL (p311) it says,
"Each device must provide a 1000-Ohm pull-up resistor on those outputs
driven by open-collector devices on the Amiga."  This seems to indicate that
I need to use a 1K pull-up on all OC's I use.  But if you had four devices
daisy-chained in a row which used the same pin, that would mean that you 
would have four 1K pull-up resistors in parallel on that line.  Is this 
supposed to happen?

Question #3:
  If I choose not to use certain input and output lines on my device, can
I simply not connect those pins?  Specificly, do all OC lines need pull-
ups?  I plan to read and write all used disk port lines (including the MFM
read and write) through a 74HCT244 buffer -- is this ok?

Question #4:
  When the sytem checks the drives using the "identification mode," the
system will receive 0000 0000 0000 0000 "no drive present" from my device.
Will disk polling continue after the system detects "no drive present?"
Specificly, if my device is connected to the Amiga external disk port and 
a standard 3.5" drive is daisy-chained from it, will the Amiga automaticly
be able to use that external drive or not?

I really appreciate any help you can give.  Thanks in advance!

-  Geoffrey Heller  gheller@luke.eecs.wsu.edu