| Boot block of prodos hard disk image [message #339042] |
Fri, 10 March 2017 21:48  |
zellyn
Messages: 173
Registered: April 2013
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Hi folks,
When CiderPress creates a prodos hard disk image, it uses a modified boot block - not the same one used on floppy disks. I can get a copy from the CiderPress source code but was curious: where does it actually come from?
Also, is there a description of how hard disks boot? Beneath Apple ProDOS describes the boot block loading and copying part of the disk card ROM into itself: is there a good description of how hard disk cards do it? Also, how to cffa does it (I assume it's the same from ProDOS's perspective?)
Zellyn
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| Re: Boot block of prodos hard disk image [message #339043 is a reply to message #339042] |
Fri, 10 March 2017 22:31  |
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Originally posted by: roger.shimada
On Friday, March 10, 2017 at 8:48:38 PM UTC-6, Zellyn wrote:
> When CiderPress creates a prodos hard disk image, it uses a modified boot block - not the same one used on floppy disks. I can get a copy from the CiderPress source code but was curious: where does it actually come from?
Apple released at least two versions of the ProDOS boot block. CiderPress looks to use the later version.
Shortly before John Brooks released ProDOS 2.4, I hacked the boot block to boot PRODOS when a 65C02 is found otherwise PRODOS1. The article is at http://roger-s-stuff.blogspot.com/2016/07/boot-block-for-pro dos-or-prodos1.html
> Also, is there a description of how hard disks boot? Beneath Apple ProDOS describes the boot block loading and copying part of the disk card ROM into itself: is there a good description of how hard disk cards do it? Also, how to cffa does it (I assume it's the same from ProDOS's perspective?)
This is really a comp.sys.apple2.programmer question, but since you asked.....
Actually, there isn't much a difference between a 5.25" boot and any other disk device. The only significant difference is that the the Disk II ROM only reads one sector, while all other devices read a block.
Typically a block device determines the number of drives attached when Cx00 is called and before reading and executing the boot block.
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| Re: Boot block of prodos hard disk image [message #339044 is a reply to message #339043] |
Fri, 10 March 2017 23:00 |
zellyn
Messages: 173
Registered: April 2013
Karma: 0
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Senior Member |
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On Friday, March 10, 2017 at 10:31:22 PM UTC-5, roger....@gmail.com wrote:
> On Friday, March 10, 2017 at 8:48:38 PM UTC-6, Zellyn wrote:
> Apple released at least two versions of the ProDOS boot block. CiderPress looks to use the later version.
According to the "Beneath Apple ProDOS" supplementary material, block zero (sectors 0 and 2) of the disk images didn't change between ProDOS 1.0.1 1.0.2, 1.1.1, 1.2, and 1.3. Indeed, they appear to be byte-identical on the ProDOS 2.4.1 disk image too.
When CiderPress creates 32 MB ProDOS volumes, it uses a different variation.
Zellyn
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| Re: Boot block of prodos hard disk image [message #339056 is a reply to message #339044] |
Sat, 11 March 2017 08:18 |
Tom Greene
Messages: 20
Registered: January 2013
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Junior Member |
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On Friday, March 10, 2017 at 11:00:37 PM UTC-5, Zellyn wrote:
> On Friday, March 10, 2017 at 10:31:22 PM UTC-5, roger....@gmail.com wrote:
>> On Friday, March 10, 2017 at 8:48:38 PM UTC-6, Zellyn wrote:
>> Apple released at least two versions of the ProDOS boot block. CiderPress looks to use the later version.
>
> According to the "Beneath Apple ProDOS" supplementary material, block zero (sectors 0 and 2) of the disk images didn't change between ProDOS 1.0.1 1..0.2, 1.1.1, 1.2, and 1.3. Indeed, they appear to be byte-identical on the ProDOS 2.4.1 disk image too.
>
> When CiderPress creates 32 MB ProDOS volumes, it uses a different variation.
>
> Zellyn
Interesting... did not realize Ciderpress was writing two different boot blocks. Both seem to work just fine for either floppies or hard disks from what I can tell.
I did a quick binary search through many of the files on Asimov. It looks like IIgs System 4.0 is probably the official origin for the newer version. The PRO.FST file contains a copy of that variant which I would expect it will use when formatting all disks. The 8-bit System Utilities uses the older block, as does Copy II+.
Tom
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| Re: Boot block of prodos hard disk image [message #339072 is a reply to message #339056] |
Sat, 11 March 2017 12:20 |
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Originally posted by: roger.shimada
On Saturday, March 11, 2017 at 7:18:06 AM UTC-6, Tom Greene wrote:
> Interesting... did not realize Ciderpress was writing two different boot blocks.
Ha...being more safe than sorry.
The only significant difference between the boot blocks in that the newer one supports a sparse PRODOS file.
> It looks like IIgs System 4.0 is probably the official origin for the newer version.
Thanks for tracking that down; I was wondering.
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| Re: Boot block of prodos hard disk image [message #339138 is a reply to message #339076] |
Sun, 12 March 2017 13:38 |
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Originally posted by: roger.shimada
On Saturday, March 11, 2017 at 12:11:38 PM UTC-6, Zellyn wrote:
> Kinda crazy to manage all that in 512 bytes... I should go read the code. :-)
You will find that a lot of the boot block is (unsurprisingly) about the Disk II block reader.
I described my findings at the previously mentioned blog link.
I was thinking of writing just about the ProDOS boot block, but I think it would have quite a small audience!
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