cheap =!cheap

[Eugen Leitl <ui22204@xxxxxxxxxxxxxxxxxxxxxxx>]

On Sat, 13 May 1995, Raul Miller wrote:

> Alternatively, even a small amount of "expensive" ram might be cheaper,
> in some circumstances, than external ram.

Exactly. Consider using 1-2 kByte fast on-chip SRAM to hold the
kernel VM. All the rest of the code sticks out into DRAM.
It would be addressed just like external DRAM, but
it would be 5-12 ns fast. Much faster than tops 60 ns external
DRAM. Effectively, we are reducing bottlenecking hot-spots.

Especially, holding data and address stack (and hell, 
why not caching code pages) in small (16-128 Byte)
SRAM segments/windows (with internal looping for code 
segments), to be swapped out at under/overflow to 
their original DRAM locations. If this introduces
additional complexity and some delay, so what. 

Software (OS) can keep page faults down. Just 
keep code page-aligned. I could live with that.

 
> [Also, I'm wondering if the desire for speed isn't obscuring what
> might be some useful techniques for implementing bulk storage.]

There is no thing like a cheap fast bulk storage. We might
get fast big optical storage with non-linear optics 
holography in 5-10 years, but currently this is SciFi.

> Raul D. Miller
> 
> 
Eugene.