XT-IDE on PCjr

Hardware questions and modifications

Re: XT-IDE on PCjr

Postby Brutman » Thu Apr 07, 2011 11:44 am

I don't have too many dead (or alive) sidecars that I want to sacrifice for a project like this. I'd really like to find a source for the connectors, but in a pinch a standard IDC connector seems to work. (Standard spacing, but 60 pins.) The original AMP connectors are available from parts dealers, but they are like $30 for a set. They are not worth their weight in gold no matter what the resellers think.

Besides, we have other things to consider. Should we stick an SRAM on it and get to 512KB? How about another 96 (128KB) to do the 736K modification? (Both would have to be options, as people might have HotShots.) What about putting the 2nd drive extra logic on the board too, kind of the way the Racores and the Creative Firmware Drive II do it? Ethernet? :-)

Do we do a sidecar, or do we just do another ISA bus adapter with a few extras on that and keep some ISA slots that we can put existing XT-IDEs on? Keeping the hardware the same as the main project might prevent headaches down the road.

Looking for input ...

Mike
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Re: XT-IDE on PCjr

Postby jmetal88 » Thu Apr 07, 2011 1:00 pm

512k should be pretty easy to add. I can give it a shot with the PCB design I'm working on.
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Re: XT-IDE on PCjr

Postby jmetal88 » Thu Apr 07, 2011 2:48 pm

I think the ISA adapter would probably be the most cost-effective approach, though. The only problem I have with it is that I'd have to leave the side plastic off my PCjr to be able to use it, unless we get creative with how it's hooked up.
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Re: XT-IDE on PCjr

Postby Spankmd » Thu Apr 07, 2011 4:55 pm

I would gladly donate a parallel port sidecar if we are looking at the multi-function board (HD, Memory, 2nd drive, ethernet?). Let me know if you would like to experiment (all I ask in return is a working sidecar once the design is done, and of course I would pay for any required parts)
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Re: XT-IDE on PCjr

Postby jmetal88 » Thu Apr 07, 2011 5:29 pm

Well, so far all I'm looking at is HD and memory (and that has the board pretty full, at least if it's to be contained entirely in the sidecar). I'm not really interested in adding second drive logic, although ethernet would be pretty sweet, so I might look into that.

EDIT: Well, a quick search didn't really reveal anything that would be easy for me to implement. I found an integrated chip with an ISA bus interface, but it needs DMA. Other chips need additional support.
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Re: XT-IDE on PCjr

Postby jmetal88 » Thu Apr 07, 2011 8:04 pm

Woah, I just found a website that has the 532771-2 connectors in stock for $1.71 apiece!

It's too bad they don't have the 532773-2 connectors. But that's half of what we would need anyway. Not sure how many they have, though, but I might try putting in a small order (5-10 or so).

EDIT: Well, I can't find the 532773-2 connectors from anyone who has a shopping cart, so I submitted a few RFQs for small quantity orders to see if I can get any at all.
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Re: XT-IDE on PCjr

Postby jmetal88 » Sat Apr 09, 2011 12:56 pm

Alright, nobody wants to sell me any of the other connectors, so a sidecar is probably out (unless people want to do them individually).

The next option would seem to be some kind of ISA box that one could attach to the PCjr via a 60-conductor ribbon cable. Then the regular XT-IDE could be used.
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Re: XT-IDE on PCjr

Postby Brutman » Sat Apr 09, 2011 1:10 pm

I'd like to get some consensus on what we're going to build, but people are being strangely quiet.

If there are others of you with opinions on what we should be thinking of, or are interesting in participating in the actual design, procurement of parts, assembly of prototypes, and testing, please speak up and make yourself known ..
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Re: XT-IDE on PCjr

Postby MattCarp » Sat Apr 09, 2011 8:03 pm

Cough, cough..... sorry, I need to subscribe to this thread!

I think your objective is not to get an ISA bus, but rather get a sidecar that has the XT-IDE controller and other things? I think that would be great. We had a little of this discussion under the "Miracle Sidecar" thread.

A single sidecar that handles all of the usual, required enhancements that minimizes the need for multiple, unsightly, power gobbling sidecars.

It would start with an IDE controller: XT-IDE electrically the same, but layout modified to fit the board, of course. If lower power part substitutes for the chips are an option, we should consider that, to minimize the power consumption and avoid pushing the internal power supply too far and eliminating the power sidecar.

512K SRAM: gotta have RAM. Just need to make sure it can hang with an 8MHz jr.

736K RAM? only mild interest from me. I can't argue against it, but I've never felt a big need to have it. I see the benefit when you allocate all of the lower 128K of memory, but I'm just not worried about it. I'd take it if it were easy/free. Maybe see if you could get it on the board, then leave it unpopulated and let the individual decide whether or not they want it.

EPP parallel port. I think this is a rather large omission in the original PCjr. With all of the built-in ports, there should have been a parallel port. So, I'd try to get this on the board. I can't believe that would be hard. That being said, I've never done it! But the cards have perhaps 8-10 logic chips that I'd think you could get on 1-2 programmable chips. A complete guess on that.

Clock calendar. If we're consolidating things, how about putting the Dallas chip here? I'd do this over the 736K mod.

Second floppy? This wouldn't be something I'd want to do. Once you get a hard disk, second floppies are just less necessary. If you really absolutely gotta have a second floppy, maybe the approach should be that you start with the Racore package and add the IDE to it? The Racore enclosure was really very well done.

Ethernet controller. This is where it's at. The Cirrus controller wouldn't be that hard to do. Mike, you're a certified BIOS programmer now? Actually, I'm not sure how much BIOS is really needed.

Hard disk. Oh yes. How about allowing someone to plug in a laptop (2.5") PATA drive right inside the sidecar? How about that? With any luck there's enough room to allow it to fit over the circuit, so we preserve the board space.


So, I guess in terms of priorities, I'd do:

1. IDE
2. Memory
3. Ethernet
4. Clock
5. Parallel port (if we ran out of room, well, one more sidecar for this doesn't completely kill me)

-Matt
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Re: XT-IDE on PCjr

Postby Vorticon » Tue Apr 12, 2011 4:12 am

Brutman wrote:I'd like to get some consensus on what we're going to build, but people are being strangely quiet.

If there are others of you with opinions on what we should be thinking of, or are interesting in participating in the actual design, procurement of parts, assembly of prototypes, and testing, please speak up and make yourself known ..

Mike, are we looking at some form of group buy here? My priority clearly is an IDE drive in any configuration. I'm afraid I have very little to contribute to the technical discussions given my lack of knowledge in this regard...
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