Quick update. I'm sad to see that Andrew doesn't have much time to work on his successor board. There is certainly a lot of merit in a self-bootstrapping design. Any PLD design has a big draw-back in that respect. I'm also glad to see DP doing their thing too as their design addresses several things not on my radar. So not to cause any confusion with the XT-IDE name, I'm simply referring to my board as the JR-IDE/ISA since it is a cut down of the board that is currently in testing over on the JR forums.
I have to unexpectedly head to Texas for the weekend for work so I can't get the first ISA prototypes (and 2nd JR prototypes) ordered this weekend. However the ISA version is completely routed and coded. Since I'll have a few more days till the next group panel buy on Dorkbot, there's time for a little design review! The schematic, board files, and BOM
are available here. When I stop in at work tomorrow, I'll add the PLD code to that file list.
This is a less feature rich board than Andrew or Ian have in mind. The DP board is coming and will include all my features plus others and hopefully some lessons learned too. So if you don't like what you see, hang on for their version. It will be better and they already have an ISA variant in live-test. The timeline for this one is going to be a couple months out for mass available kits anyway. So don't send me any IMs asking for boards. The existing BIOS principles have offered to assist with coding differences in exchange for early copper. Personally I think they sold themselves short as I was about to put 'other favors' on the table too. Couple other notes:
- Single 40 pin .1" IDE header. No 44 pin board mount or CF.
- 4 pin .1" aux power header
- Memory mapped I/O (>300 KB/s @ 4.77 MHz)
- Optional one wait state operation
- Co-layed out for 28-pin JEDEC ROM up to 32 KB or 32-pin 39SF0x0 flash part up to 512 KB with extra capacity going to a ROM disk. Though I'm tempted to cut the 28-pin socket pads.
- 16 KB dip-switch mapped dedicated ROM BIOS and register window
- 8 KB dynamically mapped panning flash access window.
- In-circuit programming via relatively cheap eBay parallel cable & free software.
It's pretty no frills. However if there is enough interest from people once a final version is ready, I'll front a batch buy of PCBs, limited parts kits, and programming cables and you can buy ala cart. Even if you don't think you have anything to contribute to reviewing the board and (tomorrow) code, don't sell your self short. An extra pair of eyes following the logic path never hurts and always reduces bugs. And I'd thank you!
-Alan