[Coco] OS-9 RAM disk with "rdisk" command? And /md descriptor?

[Allen Huffman]

> On Jan 31, 2015, at 9:39 PM, Gene Heskett <gheskett at wdtv.com> wrote:
> 
> Probably because you were out of the os9 neighborhood when I wrote that.  
> md is the descriptor that goes with myram, an automatic ramdisk I wrote 
> quite a while back.

Nope, this is the one Curtis is talking about. It allows you to dEd through memory. As soon as he said that, I remembered it. I don’t remember where it came from, though.

>  If it (md.dd) and myram (myram.dr) are in your 
> bootfile, and you issue a dir /md, there will be a slight pause, 200 
> milliseconds maybe, while it allocates the ram it needs and formats (does 
> not use the format command for this) a ramdisk whose size is determined by 
> one var in the descriptor, cyl. The dir command is held in sleep till this 
> is done, and then it wakes and dutifully reports an empty disk. The number 
> of cyl's is the number of 8192 byte blocks of ram it allocates.  None of 
> the other placeholder vars in the descriptor are used.

Clever — that’s a nice improvement over the “iniz / format” approach of most others.

> Any access, even it the first access is a write, is held until the 
> automatic formatting has been done, and then the write will be done as you 
> requested.

That’s cool The Microware official RAM disk (non-6809) was like that… iniz would set it up. In fact, format wouldn’t even work on that.

I didn’t like RBF devices that didn’t act like normal RBF devices, so while I was working for Microware, I actually wrote my own RAM disk driver called VDISK. It honored ALL the settings in the descriptor (not just the ones Microware’s did) so I could dmode it to match a floppy disk and to a “backup /d0 /r0” — something most RAM disks didn’t allow.

> The myram.README on my web page uses /r0 for the descriptors name, but 
> that clashed with the rammer/ro kit, so when it was added to the repo, the 
> descriptor was renamed to make it distinct from rammer.  Tested at up to 
> about 1.7 megabytes of usable ramdisk on my 2 meg machine.  I intended for 
> it to Just Work(TM) and I believe it does.
> 
> And when you are done, a simple deiniz /md returns every byte it used to 
> the free memory pool.  Restarting it after changing the cyl to some other 
> value does not recover what was there when it was deiniz’d.

I would expect no less from any RAM disk. Was this a problem with others? I noticed some devices I have under my NitrOS-9 boot disk CRASH if you deiniz them. That sounds like a poorly written driver to me, since you’d think the driver would just return an error in the deinit routine if it couldn’t do that.

> Enjoy Allen, I think you will like it.

I may look in to it if the one I am used to won’t work under current NitrOS-9. I liked being able to change the size with one command. I suppose if I booted with yours, and it was set to some size, in order to change it I would have to:

deiniz /md
dmode /md new settings

…then the first use would set it back up. I guess that’s not too much more than the rdisk approach but man, rdisk spoiled me.
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