Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!wuarchive!udel!rochester!cornell!johnhlee From: johnhlee@piccolo.cs.cornell.edu (John H. Lee) Newsgroups: comp.sys.amiga.hardware Subject: Re: 2320 on an A500 and external drive port hardware interfacing Message-ID: <49649@cornell.UUCP> Date: 12 Dec 90 18:04:34 GMT References: <9012120327.AA16486@yoda.eecs.wsu.edu> Sender: nobody@cornell.UUCP Reply-To: johnhlee@cs.cornell.edu (John H. Lee) Organization: Cornell Univ. CS Dept, Ithaca NY Lines: 56 In article <9012120327.AA16486@yoda.eecs.wsu.edu> gheller@YODA.EECS.WSU.EDU (Geoffrey Heller - CS216) writes: >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 In theory, I believe it's possible. In practice, I doubt it. Either way, it's definately not easy. The 2320 hangs off the video slot and picks signals off the video subsystem, not the system bus. >Question #2: [...] >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? Yes. I believe the signal drivers will sustain a 150 ohm pullup no problem, so the resulting 250 ohms pullup is fine. >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? You should probably provide pullups if you're going to connect cable to the signal line just for noise suppression. >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? From my experience with V1.3, the system will not recognize a drive after checking at the beginning of a warm or cold boot. If you extend all drive signals and rotate the drive select signals as you are supposed to, the system will recognize the external drive just fine. >I really appreciate any help you can give. Thanks in advance! You're welcome. > >- Geoffrey Heller gheller@luke.eecs.wsu.edu ------------------------------------------------------------------------------- The DiskDoctor threatens the crew! Next time on AmigaDos: The Next Generation. John Lee Internet: johnhlee@cs.cornell.edu The above opinions of those of the user, and not of this machine.