Another hardware Q

[Glenn Alexander]

On Saturday 29 March 2003 23:20, Lee Salzman wrote: 
>     SIMD would largely be a waste. However, how much does SIMD even 
> really help anything but scientific applications or the very occasional 
> 3D game? I think maybe SIMD is a little overhyped, especially if you're 
> talking about a PDA. :) 
 
That's what I was thinking. I'm likely looking at a MIPS32 chip like the  
AMD/Alchemy then. They even have a PDA reference platform that can likely be  
beaten to fit what I want. 
 
>     VLIW or superscalarness on the other hand is a lot more useful. 
 
I like the idea of just adding more CPUs for SMP. Especially if they CPUs are  
simple. That's one area Intel talks of taking the PXA chips, rather than  
to 64-bit. ARM is a bit light on registers, tho. 
 
I like the physical specs on the Crusoe and it is VLIW, but the VLIW part is  
hidden and I'm not sure if it can be brought out in any useful way. 
 
>     The trouble is that Smalltalks don't work like your average Unix. 
> You can't just swap out whole programs if you want to because there 
> really isn't such a clean notion of processes. All data is likely to be 
> strewn around the whole heap, so it can be anyone's guess where data is. 
 
I was thinking more on a per-object basis. Any object that has been unused for  
several minutes is serialised out to flash if memory is needed for something  
else. I only refered to applications out of (bad) habit and as a convenient  
term for a group of objects that work closely together to achieve a  
particular user task (and hence would likely be serialised out together as a  
matter of course, but not by explicit design). 
 
>     You'd have to fit the whole system in 16 MB, and rather than swap 
> stuff just save it to the flash mem occasionally. If the flash mem 
> wasn't flash mem, you could do a lot more, by treating the 16 MB as a 
> real cache on the 128 MB, but since you're trying to minimize writes, 
> that doesn't leave a lot of options. 
 
It's the big problem for me. I might have to use a battery-backed DRAM, though  
I prefer the simplicity of a Flash-based storage system. 
 
>     And since the implementation is not quite done yet, I'm not entirely 
> sure what you can fit in 16 MB, although certainly enough to be useable. 
 
I had assumed that might be the case since Squeak can run on PDAs with about  
that amount of DRAM. And I am hoping for a Squeak-like system as far as UI,  
functionality, etc. goes. 
 
- Glenn Alexander