Path: utzoo!attcan!uunet!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.arch
Subject: Re: RAM Disks are obsolete
Message-ID: <5830@cbmvax.UUCP>
Date: 26 Jan 89 23:49:32 GMT
References: <1374@client2.dciem.dnd.ca>
Organization: Commodore Technology, West Chester, PA
Lines: 36

in article <1374@client2.dciem.dnd.ca>, king@client2.dciem.dnd.ca (Stephen King) says:

> In article <334@belltec.UUCP> jom@belltec.UUCP (Jerry Merlaine) writes:
>>With a RAM disk, you can't re-use the RAM for something else when the
>>file system (database or whatnot) is not using it.
>>With a RAM file system, however, you can allocate RAM when the user
>>wants to store data and throw it away when the user removes files.

> Not in the Amiga. The RAM disc software that comes with the machine
> supports a dynamically resizeable disc. Write to it, and the capacity gets
> bigger. Delete a file and the disc shrinks. It is volatile storage, and
> always appears full, but it works.

The Amiga's main ram disk, RAM:, is in fact based on a file system.  The
newer, recoverable ram disk, usually mounted as RAD:, is based on a device
driver.

But one really has to ask, "how do you define a RAM disk" vs. "how do you 
define a RAM filesystem".  Certainly on the Amiga, most existing RAM
based devices are based on just plain general memory, no special custom
hardware or anything.  In that system, such a device can always grow
dynamically, but a RAM disk implemented at the device driver level can't
safely shrink, while one at the filesystem level can.  

On other systems, you may define things differently.  I suspect the
original posting was talking about custom boards designed to give you 
a RAM disk, versus software that lets you use system memory as a filing
system device of some sort.  The results being, in the latter case, you're
just running software, while in the former case, you have this special 
hardware that can't be used to directly run programs.  

>   Stephen J King   =-=   DCIEM Human Factors Division   =-=   (416) 635-2149
-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
              Amiga -- It's not just a job, it's an obsession