The DoC problem

[Bari Ari]

Bari Ari wrote:

> A flash adapter of this type is only economical is high volume. The 
> BOM and assembly costs in low volumes are higher than the cost of a 
> off the shelf motherboard unless you plan on building them yourself 
> and your time is of no or little value.
>
> A design to page out flash memory into a small space in memory is done 
> the way Expanded Memory was done for the old IBM-PC via page frames.
>
> Here's an example of how it could map into system memory:
>
> PC MAIN MEMORY LIM EXPANDED MEMORY -------------- -------------------
>
> +-------------+ | | . Extended . . Memory . . up to . /+-------------+ 
> 32M . 16M on the . // | | . '286, . / / | | . 4096M on . / / | 
> Expanded | . the '386 . / / | Memory | | | / / | | 1M +-------------+ 
> / / | Divided | | | / / | into 16K | 960K +-------------+ / | logical 
> | | Page Frame | / | pages | | 12*16K | / | | | Physical | / | | | 
> Pages | / | | 768K +-------------+\ / . . | | / . . 640K 
> +-------------+/ \ . . | Page Frame | \ . . | 24*16K | \ | | | 
> Physical | \ | | | Pages | \ | | | | \ | | 256K +-------------+ \ | | 
> | | \ \ | | | | \ \ | | | | \ \ | | 0 +-------------+ \ \ | | \ \ | | 
> \ \ | | \ \| | \+-------------+ 0
>
Sorry, the ascii drawing didn't format right, so here's a link for a 
drawing and an article on expanded memory:

http://www.eeng.brad.ac.uk/help/.dos/.expextmem.html

Bari