[Coco] nitros9 proposal - cache sector 0?

[Gene Heskett]

On Saturday 25 January 2014 12:14:14 Aaron Wolfe did opine:

> Its often been noticed that sector 0 of an RBF filesystem gets
> read/written an awful lot when doing nearly any disk I/O.  I've been
> working on the dw server some this morning and am being reminded of
> just how much.
> 
> Would it be practical to cache this sector somewhere?  256 bytes is
> not tiny, but also not impossible to find in the typical system page.
> The logic for a simple write-through cache would not be very complex.
>  I guess I'm looking to the experts for reasons this can't work or
> should never be done before looking at how to do it :)  Any thoughts?
> 
> -Aaron

1. Unless we've a huge bug, it's for reading only.  Off hand, I can only 
think of 3 programs that should write to LSN0, they are format, os9gen, and 
now my bootlink, plus any utility that opens the descriptor in raw mode, 
like "ded /d1@".

2. Its for making sure the same disk a file was opened on, is still in the 
drive before allowing a write.  The disk changed IRQ was not to my 
knowledge, ever made part of rbf.mn.

3.  So its not a great idea to cache it.

So given that, do we still have a problem?

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Cheers, Gene
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