The computer gods are pleased with your work, and rewarded you with a working power supply.
That's about the only explanation that makes any sense!
Bunsen wrote:What an epic adventure - and by the sound of it, this is just the beginning. dougg3, and everyone involved, take a bow.
Thank Bunsen! I still appreciate all the info/feedback/help everyone has given me on this project, it has been a TON of fun even through the few minor roadblocks I keep running into! It's also helping me get into hardware stuff which has always been fascinating to me.
Bunsen wrote:I gather that the barrier to using the ROM slot as storage or general-purpose expansion is the absence of any write lines?
Exactly -- I suppose we could tie into a write enable line somewhere (maybe?) and get read/write capabilities, but I don't know where to look for that or if it's even feasible -- maybe someone with more hardware knowledge would know?
Bunsen wrote: PowerPup wrote:
How the Classic's ROM disk image is implemented
gary wrote:and ROM Disk driver.
Sure, still read-only, but perhaps a convenient, OS-friendly way of making use of spare ROM capacity?
*cough* SD card?
As long as a microcontroller/FPGA or something could translate between ROM requests and SD card accesses, but the fast timing there would probably cause problems. BMOW probably knows more about this stuff and I'm suspecting that the image of what's stored on the SD card would have to be loaded into RAM that's connected to the IIci's SIMM pins--I don't think it could read off the SD card in real time fast enough (at least that's my first guess).
One small suggestion for the programming board- USB to RS232 or TTL cables are readily available, cheap, and infinitely useful for further hackery, so, in order to keep the custom board as simple (ergo, cheap) as possible, why not have TTL or serial headers on the board, and let the end user buy a USB converter? Some of us will no doubt have one lying about, and others (like me) have been meaning to get one anyway.
That also leaves the door open for maniacs who might want to program their ROM from a Mac serial port
Good idea! It also makes the board design easier for me
Since I'm going to be using a 5V microcontroller, it would be easier if I use a 5V serial port instead of 3.3V. Is that going to cause a problem? I think a lot of those types of cables are designed for 3.3V if I'm not mistaken.
Dennis Nedry wrote:I'm glad to hear that your power supply is working. Have you tested the voltages on the logic board with this power supply running? You can test +5 and +12 easily in the hard drive power connector. I'm a little bit concerned that the voltages were unstable.
I just did that...thanks for the idea.
+5V reads as 5.10 V
+12V reads as 11.89 V
-12V reads as -12.18 V
Those seem ok...maybe the IIci power supply doesn't like to be started without a load connected to it?
techknight wrote:Well if your voltages are "bouncing" that means the power supply is cycling, which means there is an overload on one of the rails somewhere. Unplug the power supply from the mainboard, measure each rail point to ground in ohms. take a note of the measurements. Go to a good board, do the same thing. what you will likely find is one or more of the rails is reading lower resistance = leakage/short somewhere. have to track it down.
Thanks for the info techknight! The weird thing is that the power supply was doing that outside of the computer with no motherboard connected to it. With a motherboard connected to it, it behaves fine. Could starting the power supply with no load cause it to choke like that and keep cycling?SIMM Update:
The second SIMM I have been having trouble with is now functional. It had nothing to do with the solder paste -- again, it was a case of nearby SIMM contacts getting shorted to each other. Possibly this time by me scraping the contacts with my probe as I was testing continuity. Something is different about the SIMM contacts than last time -- maybe they didn't coat them with solder in the revision 1 SIMMs? I'm thinking I can solve a lot of this by sucking off the solder with my desoldering gun and maybe some wick (although the wick is expensive!) Anyway, like I said earlier, I still think I will switch back to using ordinary solder and cutting out the bottoms of the sockets just to be safe. So anyway, it's coming along and I will soon be able to start selling them once I'm comfortable with them! (With the problems I've been having I want to make sure they will be reliable before I sell to anyone).