XT-IDE on PCjr

Hardware questions and modifications

Re: XT-IDE on PCjr

Postby Tempest » Sat Nov 03, 2012 1:51 pm

Quick question. How do you boot from a cartridge with the jrIDE attached? Is it even possible?
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Re: XT-IDE on PCjr

Postby Tempest » Wed Nov 07, 2012 7:08 am

I tried everything I could think of, and I couldn't get any cartridge to boot with the jrIDE attached. I'm now assuming something is being overridden and can't be undone. Is there anywhere I can get good working file versions of the PCjr cartridge games (Crossfire, Mine Shaft, Mouser, etc.)? I've found one or two but they either crashed or were really glitchy (bad sound, etc.).
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Re: XT-IDE on PCjr

Postby Brutman » Wed Nov 07, 2012 7:13 am

There is a bug in the BIOS that I inherited - even if only one hard drive is detected it is still allowing operations to the second hard drive, which of course is not there and that causes problems. Hargle confirmed the problem for me about 2 months ago.

If you disconnect the hard drive I think it will get through the boot process and go to a cartridge. I know about the bug but it wasn't a quick 2 line fix so I want to spend some time on it before releasing a fix. I'll put more priority on it though ..


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Re: XT-IDE on PCjr

Postby Tempest » Wed Nov 07, 2012 8:38 am

Oh so it's a BIOS bug? Take your time then, it's not like I'm just dying to play Mouser or anything. :)

Does anyone actually use two hard drives with the jr? Maybe we can turn that second hard drive option into 'Boot from cartridge'?
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Re: XT-IDE on PCjr

Postby Brutman » Wed Nov 07, 2012 12:37 pm

Yes - it is definitely a BIOS bug. When I put in some debug code to find it it started working, so I know it is specifically related to leaving a flag on after reading the parameter table when searching for a device to boot from.

You do bring up an interesting point - the menu option for BASIC says to boot ROM BASIC. That does not cover booting directly from a cartridge. The cartridge space starts higher in memory than the IDE option ROM so there does not seem to be a way to boot to something else besides ROM Basic. In theory the ROM BIOS area scan should continue and find any cartridges up there, but if they are hooking INT19 (the BASIC interrupt) that is not going to work - your hard drive will be found first and it will boot from that instead. (Which is why disconnecting the hard drive makes it work ... the INT13 boot fails and then it goes to ROM BASIC.)

I'll dig ...
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Re: XT-IDE on PCjr

Postby Tempest » Wed Nov 07, 2012 6:07 pm

I tried booting a cartridge by disconnecting the hard drive and it didn't work. It just went to the disk drive and eventually timed out. The cartridge was never booted.
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Re: XT-IDE on PCjr

Postby Brutman » Mon Nov 12, 2012 10:08 pm

It is fixed - see the newest post in the BIOS updates thread.

Some cartridges will run without waiting for the machine to complete the scan of the ROM areas and go through the Int 19 bootstrap routine. Demon Attack is one of those, and those would not have been affected by the bug.

Other cartridges (MineShaft, Cartridge BASIC, etc.) can be selected now through the boot menu. The machine will try to boot from the floppy drive, then the hard drive if it is found. If neither are found it goes to BASIC ROM, or to whatever cartridge is in place. If the hard drive is found and bootable you will have to use the boot menu to skip booting from it to go to the cartridge.


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Re: XT-IDE on PCjr

Postby Trixter » Wed Apr 17, 2013 9:22 pm

jmetal88 wrote:
alanh wrote:I did get a valid signed quote back from State Electronics for AMP 532773-2 (60 pin stacked box connector) $8.90 and AMP 532771-2 (60 pin shroud) $0.75. I think I might order 25 of each to have on-hand. I have another request for quote out. Going to wait for it first. Would save tearing up side-cars.


I'm afraid I need a pair of these -- In trying to take one of my jrIDEs off, I noticed the connector was very loose; in trying to push it back together and also trying to get it back onto a PCjr, I have just about mangled many of the female sockets and I am deeming it useless. I went to State Electronics' website but searching for those part numbers doesn't turn up anything (I was visiting http://www.state-elec.com/). Is there another way to source these, or am I going to have to try desoldering them off of other sidecars?

This was for packing up my PCjr for the talk I'm giving on Saturday, but thankfully I have a second jrIDE and was able to put that into a shell, move the DOM over to it, flash the BIOS up, and I'm back in business for my talk. But I still want to repair the other one.

Also, I'm pimping the jrIDE in my talk on Saturday -- are there many kits/boards left? I don't think my talk will cause hundreds to rush out here, but there could certainly be single- or double-digit interest.
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Re: XT-IDE on PCjr

Postby Brutman » Thu Apr 18, 2013 6:14 am

Being a paranoid hoarder I tried State to get a few connectors after Alan did. They charged my card, and then a month later I had to ask them where the parts where. They could not find them so they refunded the money, but I was slightly irritated that a month had to pass and I had to go hunting first.

State might still have them, but they might be lost in their warehouse. Or their inventory control was wrong and they are gone ...

They are not soldered - it is all friction fit. It takes a while to pry a set apart; I used an old parallel sidecar that was dead as a donor board.

Another thing to keep in mind is that the pin spacing is standard IDC, like that used on IDE cables. You don't get the nice box and socket of the AMP pair, but IDC connectors can be made to work.
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Re: XT-IDE on PCjr

Postby alanh » Thu Apr 18, 2013 7:24 am

BTW, to get those connectors together, I found the best way is to put them together around the board like they are intended to work, place the female side down on a flat surface while supporting the rest of the board with your hand, leave the shrouded male side pointed up in the air, then take a rubber mallet to the male shroud. It's all friction lock. They will come together.
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