XT-IDE on PCjr

Hardware questions and modifications

Re: XT-IDE on PCjr

Postby alanh » Sun Sep 09, 2012 4:19 pm

Might be next weekend, but I'll get you the exact model numbers of everything I've tested. I'm on a business trip from early Monday morning till late Thursday.
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Re: XT-IDE on PCjr

Postby jmetal88 » Sun Sep 09, 2012 5:47 pm

IBM-DBOA-2540. 2.5" laptop hard drive. 540MB. Works perfectly.

I had an 80MB hard drive out of a Zeos laptop that I tried to use earlier, and that didn't work. The JR-IDE BIOS gave a message about the drive being too old (I think it meant it couldn't detect the geometry of the drive, since it was designed for a computer that used hard drive 'type' numbers).
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Re: XT-IDE on PCjr

Postby Brutman » Sun Sep 09, 2012 6:03 pm

Yeah, don't do that. :-(

The BIOS is designed with newer drives in mind - it is using LBA addressing on the drives. Going back to a pre-historic IDE drive that only understands CHS kind of defeats the purpose, which is to get to use newer/modern drives that might last a little longer.

I'm running with a Maxtor 20GB and a Maxtor 30GB drive. I've also used a Hyperdisk 512MB Disk On Module. And I know that Jeff uses an 8GB KingSpec DOM.


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Re: XT-IDE on PCjr

Postby Vorticon » Sun Sep 09, 2012 6:14 pm

I'm just using a 250meg CF card. I know that it has a limited life depending on the amount of write cycles, but it is compact and quiet. Besides, after the initial transfer of files to the CF, most of what I do on the Jr requires reads only, so it should last me a good while.
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Re: XT-IDE on PCjr

Postby Brutman » Sun Sep 09, 2012 6:51 pm

I just did a little digging around and tried a 6GB Western Digital drive on the jrIDE. Needless to say I was annoyed when it told me that the drive was too old and crappy to be used. ;-0

The ATA-2 specification (1996) recommends that all drives over 528MB implement LBA addressing, but it is optional. Apparently it is not required until ATA-3 or your drive is above 8GB in capacity. If LBA addressing is not supported in the drive then the host has to use CHS addressing. The CHS addressing can be mapped to something that can use the entire drive, but it is still CHS addressing.

Unfortunately, the BIOS only uses LBA addressing. It's not impossible to modify the BIOS to handle CHS addressing if LBA addressing is not available, but it requires a bunch of new code and a lot of testing. Nobody wants their data scrambled ...

So for now, use a drive from a reputable vendor. ;-0
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Re: XT-IDE on PCjr

Postby Eric » Mon Sep 10, 2012 3:13 pm

Brutman wrote:I just did a little digging around and tried a 6GB Western Digital drive on the jrIDE. Needless to say I was annoyed when it told me that the drive was too old and crappy to be used. ;-0

/this

XD
PCjr:
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Re: XT-IDE on PCjr

Postby Hargle » Mon Sep 17, 2012 7:05 am

three solutions for the lack of CHS support:

1) add CHS support to the BIOS. Lots of work for Mike and/or me. Lots of bugs, corrupt drives, time taken up that could be used for other things.
2) port a version of the XTIDE universal BIOS over to the jr. Only slightly less work for Mike, Me, and/or Tomi, but would be awesome to have this platform supported in that code base. Would make for the highest compatibility of drives on this platform. The XTIDE universal BIOS is way overkill for this platform.
3) use a modern drive/CF/DOM. No work at all, and if you really can't find a modern drive to use, you are not looking very hard. you should be able to 8 gig drives on craigslist at 50 cents per bushel!
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Re: XT-IDE on PCjr

Postby jmetal88 » Mon Sep 17, 2012 8:43 am

Hargle wrote:three solutions for the lack of CHS support:

1) add CHS support to the BIOS. Lots of work for Mike and/or me. Lots of bugs, corrupt drives, time taken up that could be used for other things.
2) port a version of the XTIDE universal BIOS over to the jr. Only slightly less work for Mike, Me, and/or Tomi, but would be awesome to have this platform supported in that code base. Would make for the highest compatibility of drives on this platform. The XTIDE universal BIOS is way overkill for this platform.
3) use a modern drive/CF/DOM. No work at all, and if you really can't find a modern drive to use, you are not looking very hard. you should be able to 8 gig drives on craigslist at 50 cents per bushel!


I like option #2. Option #3 works as well, but having the two projects tied together would be pretty neat.
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Re: XT-IDE on PCjr

Postby dan2304k » Mon Sep 17, 2012 9:52 am

Image

:mrgreen:

I see value in #2, however, I agree completely that with the variety of options for obtaining drives that work with the current implementation, there are very likely other tasks which would be a better use of limited time!

I am using a CF card with CF to IDE adapter, and this works wonderfully. Given the frequency of writes for me, I am not concerned about flash lifefime. For anyone who is concerned, it's a simple task to occasionally pull the CF card and create a back-up!
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Re: XT-IDE on PCjr

Postby Trixter » Mon Sep 17, 2012 11:46 am

Hargle wrote:3) use a modern drive/CF/DOM. No work at all, and if you really can't find a modern drive to use, you are not looking very hard. you should be able to 8 gig drives on craigslist at 50 cents per bushel!


This. It's the least amount of effort for all parties involved for the most amount of gain.

Forget 8gig drives, you can use anything -- 20 gig, 160gig. Yes, the extra space will go unused, but you weren't using the drive for anything anyway, right?
You're all insane and trying to steal my magic bag!
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