Re: Update IDEJD6
Date: 2008-04-15 10:59:36

On 2008-04-14, at 19:14, Jim Brain wrote:

> I stil think 256 byte sectors are the most compatible (How do you  
> reference loading from the 257th byte of a sector using B-R or U*  
> commands?).  Yes, you can ignore such things, but I think it's  
> trivial to handle 256 byte logical sectors in a 512 byte physical  
> sector environment.  uIEC and sd2iec do it and it does not take lots  
> of extra RAM. 1581 did it as well.

256 bytes _is_ the most compatible but is it the best? This very much  
reminds me of the similar discussion in the 8 bit Atari circles. And  
it ended up with various projects using three different approaches:

1. mapping directly 1:1 the 512B hardware blocks into 256B filesystem  
+ very fast
+ compatible
- 50% waste of storage

2. using full 512B blocks of the hardware medium directly in the  
+ even faster
+ efficient medium usage
- incompatible

3. emulating 256B blocks with two halves of 512B hardware blocks
+ compatible
+ efficient storage utilisation
- longer TTM
- slow

Now, having look at the above and keeping in mind what are the goals  
of this project (efficiency and compatibility - to my understanding)  
while not aiming at breaking speed records (for that there is IDE64  
and here we are limited with the connection method anyway) it seems  
almost obvious which approach suits the purpose best (have both on  
plus side). There is - however - a need for extra buffer if we want to  
keep the compatibility plus more extensive development and testing for  
various test cases required.


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