Fm: Jim Unger 72747,1217 To: Wayne Day 76703,376 Wayne, I took your advice of a couple days ago and checked the DIP switches in my SX. They were all up (on), swith #2 therefore indicating my internal HD is using IRQ 2. I decided to call Aerocomp to find out how to change the controller to use IRQ 5 like an IBM. But first, I flipped DIP #2 down (off) just to see what would happen. Well, nothing happened--the computer booted and ran fine! Surprised the *!#@! outta me! So I left the DIP down/off. Does this now mean I can just plug in an EGA card that uses IRQ 2? And how come the controller still works? Jim (boy am I confused) Unger >>Fm: Wayne Day 76703,376 Hmmm... interesting. Don't know what kinda setup they're using on the Aerocomp system, but my Adaptec/Seagate definitely wouldn't work that way. Sounds like you got lucky! I'd guess the next thing is to try the EGA card to see whether your luck holds! Wayne who knows that there are SOME questions that just don't have answers! >>Fm: Jim Unger 72747,1217 Wayne, I spoke to a technician at WD today, who told me that since my controller was configured to use IRQ 2, it didn't matter at all whether IRQ 5 was enabled/disabled. He said that I was confused (mildly put). Turning DIP #2 (IRQ 5) OFF does NOT disable 5, it merely enables an external device to use that interrupt with no interference from another device. I also spoke to a tech at Aerocomp who informed me that the WD1002-27x controller is easily changed to use IRQ 5; this I did, and flipping DIP #2 to OFF (DISabling IRQ 5) enabled the controller to work, using IRQ 5. Therefore, I can now use an EGA/VGA board that uses IRQ 2. BTW, the Everex Micro-Enhancer #657 or 659 is switchable between IRQ 2 or 3. One major note: The Tandy EGA board (25-3048) uses IRQ 5, so if you've got a standard PC hard drive in your SX/TX, beware! (A std PC drive uses IRQ 5, also). The worst part is I think I'm beginning to comprehend this modern Sanskrit...anyway, the Everex Micro-Enhancer works on the SX or TX because it's jumper-configurable to use IRQ 2 or 3. So no conflicts should arise regardless of your hard drive type. Jim Fm: Richard W. Doig 73767,32 Jim, you are going through the same thing I did about 10 months ago. I'm a mechanical engineer, not an electrical, but here is what I've learned in reading through the 1000SX tech manual and experimenting. 1. An 8-bit machine also appears to have 8 input paths available. In mechanical terms, 8 wires connecting into the circuitry. 2. For whatever reason, these are called Interrupt Request Lines or IRQ's for short. They are numbered 0 through 7. 3. On a 1000SX or TX , they are connected as follows: #0 Software Timer #1 Keyboard #2 Connected to the bus #3 Connected to the bus #4 Connected to the bus #5 Connected to the bus and internal video circuitry #6 Connected to the bus and internal floppy drive controller #7 Connected to the bus and internal printer port circuitry 4. What they call the bus is a series of 5 expansion slots all connected in parallel. The six available interrupts are actually six specific pins in each slot. So if you have a device that can't be jumpered, you can tell what interrupt it uses by looking at the card edge connections on the board if need be. 5. The switch block in the SX and TX is one on-off switch and three jumper switches. Switch #1 turns off the on-board video circuitry. Switch #2 normally jumpers IRQ5 back into the internal circuitry. Switch #3 jumpers IRQ6 back into the internal circuitry. And switch #4 jumpers IRQ7 back into the internal circuitry. 6. The net result is that switches #1, #3, and #4 act like on-off switches for the internal video, internal floppy drive controller, and internal printer port respectively. The oddball is switch #2. 7. It appears that switch #2 shorts the IRQ5 connection in the expansion slots. If you turn it to off, it severs this short. It further appears that the system only actively uses this connection when using the expanded video modes available on the 1000 series. 8. Further, they have arranged it so that a hard drive controller and the on-board video can co-exist using the same interrupt. You actually replace the straight-through connection in the switch with the hard drive controller. 9. Tandy's hardcard can be set for IRQ5 or IRQ2. I've used mine set for IRQ5 for about 10 months now with no problems at all. I just parked the drive, took it out of the case, changed the jumpers and re-installed it. I turned switch #2 to off while I had the case open. I booted up and ran normally. All the video modes work as well. 10. Incidentally, I thought that Tandy had dropped the list price on the 20 meg Hardcard to $599.00 last fall. Merrymac (GO MM) sells this same card for $459.00 the last time I looked. I hope this helps. Rich >>Fm: Tom Baden 74646,676 Jim, The way I read the Everex manual I can use any IRQ. The picture on page 32 shows EXamples of the setup for IRQ2 and IRQ3. I just got my TX today so I'm going to try using IRQ5 so that my Zuckerboard hardcard can work on IRQ2 and mey Microsoft Mouse will work on IRQ3. Wish me luck. Tom >>Fm: Jim Unger 72747,1217 Tom, As I understand it, you should have no problem with that configuration. That is as long as no EXTERNAL device attempts to use the same IRQ as some other device. Put simply, if some un-named device (software or hardware) needs to use IRQ 5, for example, and your HD or software requires the same interrupt, then there's gonna be a conflict. Fortunately, in the PC world, some of these things are standardized...a standard PC uses IRQ 5 for it's Hard Disk; most video cards use IRQ 2. The only reason the question arose at all (for me) was that I have one of the more PC-compatible 1000s from Tandy. The original T1k & T1ka used IRQ 2 for hard drive; so it required a drive controller specifically setup for that computer. If you stuck a standard PC HD/Controller in the T1k/A, it bombed 'cause it wants IRQ 5, and there's no way to disable IRQ 5 on the original T1ks. On the SX/TX, you just flip motherboard switch #2 to OFF; Bingo, IRQ 5 is now disabled for all inputs EXCEPT the external device. Since the Everex Micro-Enhancer can be configured to IRQ2 OR IRQ 3, it should present no insurmountable problem, regardless of hard drive IRQ 2 or 5. I have the jumper changes necessary to convert a WD1002-27x controller from T1k to PC/XT compatible, if anyone's interested. Jim PS: Since my info is based solely on an intense study and telephone conversations with engineers/techs, I'd welcome comments from some of the hard/soft wizards lurking around here. Like Ray and Mike and Horace and Wayne and -jjkd- , etc. >> Fm: Tom Baden 74646,676 Jim, Add IRQ5 to the list, last night I booted off of my ex-T1KA harddrive (I (IRQ2) and ran GEM using my Microsoft Mouse (IRQ3) and the Everex driving a CGA monitor (IRQ5). No problems, except that Starflight wouldn't use the card and monitor. I've pulled the card until I get a Multi frequency Monitor to use the extended EGA capabilities. All I need to do now is install the 5 1/4 drive sitting here on the desk and wait until the local electronics store gets some 256k drams. Tom Fm: Jim Unger 72747,1217 Wayne, The reason your Seagate/Adaptec combo WON'T work in both DIP #2 positions is that your Adaptec controller is factory-set to use IRQ 5. Therefore, that motherboard switch Enables/Disables the interrupt your controller needs. Had you bought a HD/Controller combo already configured to use IRQ 2 (Tandy 1000 standard), that IRQ 5 switch would have no effect since your controller doesn't need or use it all. Hey Wayne--I'm no hardware wizard, but I've made an intense effort to get the true grit on this stuff the last couple o' days, talking to all species of deranged hardware types. I've actually reached the stage where I recognize a semi-literate tech on the phone who knows even less than I do...and they usually say "Lemmee connect you with an engineer..".... Well, nothin's really new uder the ol' sun...I s'pose that if you wanted to run around in one of them there horseless carriages long about 1903, you had to be a machinist, a mechanic, or just a masochist!! No normal person would be seen dead in a contraption like that. Jim