gheller@YODA.EECS.WSU.EDU (Geoffrey Heller - CS216) (12/12/90)
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
daveh@cbmvax.commodore.com (Dave Haynie) (12/13/90)
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. The A2320 (or any such device) doesn't sit on the system bus, it glomps on to the video bus generated by Agnus and Denise. To physically hook this to your A500, you would have to find a way to run the 12 digital video pixel bits from Denise, the syncs from Agnus, and a couple of power supply lines up to the A2320. Assuming it doesn't use -5V (which isn't on the A500), it might work, though it would be a rather ugly mess of wires, and you would have to figure out how to internally mount the thing. And you may very likely get into power supply loading problems on the A500. Scott Hood could tell you more about that. >If not, would anyone care to recommend a solution to the flicker problem on >A500's? The main problem with frame converting an A500 display is that you can't easily get to all 12 bits of digital video. An internal device can jumper over to them somehow, but anything external would have to use the analog RBG lines and run them through video ADCs before frame buffering. That's going to cost more than the digital solutions used in the A2000 and A3000. >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? With four devices, that's 250 ohms per line. Not a big problem for your typical open collector buffer. They would probably work, like SCSI, if you only terminated the endpoints of the floppy lines, but I imagine the 1K value was chosen to handle 1 to 4 devices, each with their own termination/ pullup resistors. >Question #3: > If I choose not to use certain input and output lines on my device, can >I simply not connect those pins? If you're not providing passthrough, and your lines aren't too long, it'll probably work OK. It wouldn't hurt at all to provide pullups, though, for the shared lines you're not using. >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 can buffer inputs to your device with a 74HCT244, but you can't drive the floppy bus with that one, it's not an open collector or open drain device. A common 7407 chip gives you 6 non-inverting open collector buffers in a 14 pin package, a bargain at twice the price. >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? The Amiga will look at each of the four floppy channels independently, so if your device doesn't identify itself as a floppy, but the next one does, the next one will get added automatically. Much like what normally happens in the A2000 with one internal and one external floppy -- unit 0 is automatic, unit 1 (second internal drive) isn't there, but unit 2 gets added as an external anyway. >- Geoffrey Heller gheller@luke.eecs.wsu.edu -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "I can't drive 55" -Sammy Hagar
johnhlee@piccolo.cs.cornell.edu (John H. Lee) (12/13/90)
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.
vincelee@tornado.Berkeley.EDU (Vincent H. Lee) (12/20/90)
In article <49649@cornell.UUCP> johnhlee@cs.cornell.edu (John H. Lee) writes: >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. Don't listen to my brother. I'm planning the same modification. Issue 1.5 of AmigoTimes showed how to connect a MicroWay Flickerfixer to a 500. My guess is that connecting a 2320 should be similar, but I will have to see if it needs any additional signals. The flickerfixer just needed the 12 digital color signals (available on buffer chips U40 and U41), horizontal and vertical sync (RP 403), a clock signal (RP103), +5, and ground. The 2320's mileage may vary. > John Lee Internet: johnhlee@cs.cornell.edu >The above opinions of those of the user, and not of this machine. -Vince Lee
hood@cbmvax.commodore.com (Scott Hood) (12/21/90)
In article <1990Dec20.082254.16766@agate.berkeley.edu> vincelee@tornado.Berkeley.EDU (Vincent H. Lee) writes: >In article <49649@cornell.UUCP> johnhlee@cs.cornell.edu (John H. Lee) writes: >>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. > >Don't listen to my brother. >I'm planning the same modification. Issue 1.5 of AmigoTimes showed how to >connect a MicroWay Flickerfixer to a 500. My guess is that connecting a >2320 should be similar, but I will have to see if it needs any additional >signals. > >The flickerfixer just needed the 12 digital color signals (available on >buffer chips U40 and U41), horizontal and vertical sync (RP 403), a >clock signal (RP103), +5, and ground. The 2320's mileage may vary. > >> John Lee Internet: johnhlee@cs.cornell.edu >>The above opinions of those of the user, and not of this machine. > >-Vince Lee Add Csync to that list as well and that should be it! Have fun and Happy Holidays, Scott Hood -- -- Scott Hood, Hardware Design Engineer (A3000 Crew), Commodore-Amiga, Inc. {uunet|pyramid|rutgers}!cbmvax!hood hood@cbmvax.cbm.commodore.com "The views expressed here are not necessarily those of my employer!"