Re: virtual memory, possible solution ?

[Stephan Haslbeck <haslbecs@informatik.tu-muenchen.de>]

On Sun, 18 Dec 1994, Theo Janssen wrote:

> Hi there !
> 
> A fews days ago i found a small lib called "VMEM" which includes
> "virtual memory stuff" for the ST. PERHAPS ?!?! this library COULD BE
> a temporary solution for the MiNT virtual memory Problem.
> I didn't tried it out or inspected the sources yet, because i am very busy
> at the moment. Maybe the "Kernel-professionals" should have a look at
> this stuff and it's possibilities. After a short look into the manual
> i can say the following:
> 
> advantages:
> 
> - does NOT need an MMU. So even 68000 machines should be able to use it.
> 
> disadvantages:
> 
> - Applications have to be recompiled, cause the lib uses sepcial
>   "VM_ALLOC, VM_LOAD, VM_FREE ...." calls
> 
> - Manuals and Descriptions only available in german language

That's not a problem for me... ;-)

> 
> But as i said, PERHAPS this is a solution. So please don't hit me
> if this stuff is not usable. ;-)

Even as a temporary solution it's not useful. You would have a dozen of
programs running with this pseudo virtual memory, und hundreds others which 
don't. You'll have to insert those VM_* calls, recompile everything, perhaps 
debug because of incompatabilities, ... much work! Would you do it?

The goal of virtual memory is that you don't have to change existing
software!
So it's the task of the kernel to implement this. Or do want every 
program to have its own receipt of swapping, perhaps with its own
hard disk driver? No, sorry. 

We need interrupt driven disk drivers and a kernel aware of virtual
memory. All or nothing. And not some incompatible hack. That's my
opinion. Very bad the 68000 having no MMU! :(

> 
> The archive is called VMEM.(ZIP, LZH, ZOO or whatever). At the moment i
> cannot remember where i found it, but should be available on some
> german FTP-Servers.

Perhaps it's useful for programs using VERY MUCH memory, such as graphics
programs.

> If it's necessary i could send the stuff here (apr. 70 kB).
> 
> 
>          cheerio Theo

Ciao,
Stephan


+------------------------------+-----------------------------+
|      Stephan Haslbeck	       |    Fachschaft Informatik    |
|       Agricolastr. 61	       |   Technische Universitaet   |
|      D-80686 Muenchen	       |      Muenchen, Bayern	     |
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