SD-Cart JR: An MMC/SD card reader cartridge

Hardware questions and modifications

Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby Trixter » Wed Dec 02, 2020 2:05 pm

I ordered a 2GB SD card, so I can't test until it arrives.

I don't want smaller sizes -- I want larger :-) My jrIDE has an 8GB DOM in it, divided into C:, D:, E:, and F:.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby bloguidice » Wed Dec 02, 2020 3:09 pm

raphnet wrote:Speaking bootstraping a PCjr using the cartridge, one thing I would like to offer is a bootable cartridge supplied with a memory card pre-loaded with a version of DOS... But I would need a version of DOS that is 1. OK to distribute and 2. Works on the PCjr..


I would hate for (1) to be an impediment to release of such a thing. Microsoft DID release the source code to MS-DOS 1.1 and 2.0 in 2014: https://computerhistory.org/blogs/micro ... -v1-1-v2-0

"You may use, copy, compile, and create Derivative Works of the software, and run the software and Derivative Works on simulators or hardware solely for non-commercial research, experimentation, and educational purposes. Examples of non-commercial uses are teaching, academic research, public demonstrations, and personal experimentation. “Derivative Works” means modifications to the software, in source code or object code form, made by you pursuant to this agreement."

I would say this falls under the threshold of commercial use into non-commercial use. This is small run stuff and no code is being modified. And you're not actually selling the software itself.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby Trixter » Wed Dec 02, 2020 4:17 pm

The only issue with DOS 2.0 is that it has limited support for hard drives; FAT12 limits the partition to 32MB. It's not the end of the world; without extended partition support, I believe you can use all four primary partitions to have c:, d:, e:, and f: existing, all 32mb. So 128MB total. But yes, I'd agree with the license that usage like this is allowed. However, it would have to be "extended" to include PC-DOS 2.1 instead of MS-DOS 2.0, since PC DOS 2.1 added support for running programs off of ROM carts -- so single-cart applications like Colorpaint could still run if PC-DOS 2.1 is used.

There's always the "economic recovery" rule: When a product is completely beyond economic recovery for a corporation, they lose all financial interest in it. Distributing free copies of a patched MS-DOS 6.22 on a bootable PCjr cartridge is extremely unlikely to get anyone's attention at Microsoft.

I wouldn't bother with FreeDOS at all. It was created primarily for 386+ systems and is extremely difficult to get running on 808x, and also quite slow.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby bloguidice » Wed Dec 02, 2020 9:40 pm

Trixter wrote:The only issue with DOS 2.0 is that it has limited support for hard drives; FAT12 limits the partition to 32MB. It's not the end of the world; without extended partition support, I believe you can use all four primary partitions to have c:, d:, e:, and f: existing, all 32mb. So 128MB total. But yes, I'd agree with the license that usage like this is allowed. However, it would have to be "extended" to include PC-DOS 2.1 instead of MS-DOS 2.0, since PC DOS 2.1 added support for running programs off of ROM carts -- so single-cart applications like Colorpaint could still run if PC-DOS 2.1 is used.

There's always the "economic recovery" rule: When a product is completely beyond economic recovery for a corporation, they lose all financial interest in it. Distributing free copies of a patched MS-DOS 6.22 on a bootable PCjr cartridge is extremely unlikely to get anyone's attention at Microsoft.

I wouldn't bother with FreeDOS at all. It was created primarily for 386+ systems and is extremely difficult to get running on 808x, and also quite slow.


I agree, and for that matter PC DOS 2.1 already came with drive-based PCjrs, right, so it's not like anything would be given that's not already there? I really don't see the harm or danger. It's very low scale and not profiting off of the software in any way.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby Fenyx4 » Mon Dec 07, 2020 9:29 pm

Got mine today! Updated config.sys, popped it in with an SD Card and worked great!

Updated my config.sys, inserted the SDCart, inserted the SD card and boom! All good!

This SD Card worked great!
https://www.amazon.com/gp/product/B000WHFMR2

This SD Card not so much.
https://www.amazon.com/gp/product/B00FYX1ABQ

I get a "No suitable partition found.Init failed" error.
I tried reformatting the SD card, tried wiping the partition and recreating it and it didn't work.

I also created an image of the working SanDisk SD Card with Win32 Disk Imager and writing it to the not working Transcend card. Doing so gave me some errors about the Transcend card not being big enough for the image but it worked well enough for me to get a dir. But it gave me a lot of random "Not ready reading drive" errors and I had to retry a lot.

Thanks this is really awesome. Nice to have something that I can pop in and out even more easily than the CF card in the jrIDE.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby Fenyx4 » Mon Dec 07, 2020 9:47 pm

P.S. Just for funzies I did try some SD Cards that are too big. They had a "Divide overflow" error.

Interestingly after trying those swapping to the working one didn't work anymore. It started having a "File allocation table bad, drive D". Had to reboot to get it working again.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby raphnet » Mon Dec 07, 2020 11:08 pm

Fenyx4 wrote:This SD Card not so much.
https://www.amazon.com/gp/product/B00FYX1ABQ

I get a "No suitable partition found.Init failed" error.
I tried reformatting the SD card, tried wiping the partition and recreating it and it didn't work.

Could you try running sdpart.com to see what kind of card it is, and what spec version it conforms to? Also please use the 'p' command to print what the partition table looks like.

I will release a new version soon, with support for large cards. Those already work now, but I just noticed a major problem. In sdpart.sys
reading/writing from sector 65536 and above does not work at the moment, and with a >32M partition, after you add over 32M of files, it becomes a problem!

This is because I implemented the driver using the documentation in the DOS 2.0 source code... :oops: Now I see the read/write requests were extended in later versions of DOS to use a 32 bit starting sector field, so it will be an easy fix.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby Fenyx4 » Mon Dec 07, 2020 11:25 pm

raphnet wrote:
Fenyx4 wrote:This SD Card not so much.
https://www.amazon.com/gp/product/B00FYX1ABQ

I get a "No suitable partition found.Init failed" error.
I tried reformatting the SD card, tried wiping the partition and recreating it and it didn't work.

Could you try running sdpart.com to see what kind of card it is, and what spec version it conforms to? Also please use the 'p' command to print what the partition table looks like.


I get this with sdpart.com;

Code: Select all
SDpart version 0.2
Partitioning tool for SD-Cart JR
Running on DOS 5.0

Initializing card... OK
Error reading boot secotr


So sadly I can't get to the 'p' command.
This is from a freshly opened one without me having messed around with it.
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby raphnet » Tue Dec 08, 2020 1:10 am

raphnet wrote:So sadly I can't get to the 'p' command.
This is from a freshly opened one without me having messed around with it.

Please try the new release (v03). I modified sdpart.com to display card information before attempting to read the MBR. Maybe it will show something that will help me understand how I could support it...
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Re: SD-Cart JR: An MMC/SD card reader cartridge

Postby raphnet » Tue Dec 08, 2020 1:13 am

Release v03 is now available. Large cards are now supported, and there is an important bugfix for partitions larger than 32M using sdcart.sys!

  • Add support for block-addressed cards (For cards >2GB)
  • Implement >32M partition support in sdcart.sys
  • Add a 'low memory' version of sdcart.sys (sdcartl.sys). Sacrifices speed for using only approx. 3kb of memory instead of approx. 9kb.
  • sdpart.com : Display card information before reading the MBR

Available here: https://www.raphnet.net/electronique/sd ... x_en.php#3
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