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RAM Doubler is a replacement for Apple Virtual
Memory.
From the viewpoint of "memory", Connectix RAM
Doubler VM provides the same features as Apple VM, and thus the
advice on our page "Should I use VM?" applies
to RAM Doubler as well.
This explains why you find comments like
this slip into the few RAM Doubler docs that exist:
TESTING
WITH APPLE'S VIRTUAL MEMORY
Next, try turning on Apple's Virtual Memory in the Memory Control and
restart the Macintosh. If the same problem occurs with Apple's Virtual
Memory, it is also very likely to have the problem with RAM Doubler since
each employs a form of extended memory. It would then be necessary in
this case to determine which software is not working properly with extended
memory in use.
And comments like
this:
INCOMPATIBILITIES
WITH EXTENDED MEMORY
If RAM Doubler is installed, there are a few programs (usually old ones)
that might see "extended memory" and assume that Apple's Virtual Memory
is in use, even if it is actually RAM Doubler that is providing the extended
memory. If a program is not designed to work with extended memory in use
and RAM Doubler is installed, it may display a message that says "Virtual
Memory is on" and that it should be turned off. If this occurs, there is
a
simple alternative. Restart the Macintosh and disable RAM Doubler
temporarily by holding down the tilde (~) key or the escape (esc) key during
startup. This will disable RAM Doubler for that session. RAM Doubler will
reload on the next restart.
Connectix would lead you to believe that these comments are coincidental,
when in fact RAM Doubler's "extended memory" is simply virtual memory -
and thus the common problems are not coincidental. Like all virtual memory,
RAM Doubler employs the processor's Memory Management Unit to provide a
virtual memory address space, handling interrupts to service memory needs
using real memory and backing store. Call it "roses", but it is still VM
(which is a valuable item in its own right), and it is not RAM Charger.
(Humor: perhaps you will find it
as ironically amusing as we do that our artificial arch competitor now
seems to be the only virtual memory solution that allows users to use VM
and RAM Charger under OS 8.5.1 and 8.6! Ha! Ha! - read more here)
However, there are a few issues that might make you choose either Apple
or Connectix over the other. If yo are so inclined, a somewhat less technical
approach to this topic is taken on the web page "How
does RAM Charger compare to RAM Doubler (virtual memory)?". But, since
Connectix is never up front about the technical issues, here is the real
stuff so you can make an informed choice.
Despite all other claims about "how" RAM Doubler does what it does (claims
that are unimportant to the end user, and claims that are often contorted
and/or misrepresented to make it sound impressive), and Connectix's attempts
to coin the term "extended memory", RAM Doubler VM has only four significant
differences from Apple VM:
In Favor of RAM Doubler
1) RAM Doubler VM doesn't reserve disk space, and is less likely
to spin your disk.
2) RAM Doubler VM claims to be faster than Apple VM.
** It may be the only way to run VM and RAM Charger under OS 8.5/6 (read
here)
Against RAM Doubler
3) RAM Doubler (2) VM provides five VM sizes, Apple VM sizes
are unlimited.
4) RAM Doubler costs money, Apple VM comes free with your system.
Details
1) If you do not care about hard disk space, #1 is unimportant
- unless you are running a notebook and may care about battery life. Apple
reserves a portion of your hard disk eqaul to the amount of virtual memory
set in the "memory" control panel. And, because of the techniques it uses,
apple is more likely to spin your disk more often. RAM Doubler can go much
farther before needing to use any disk space, and it does not reserve the
disk space in advance.
2) We have never seen any benchmarks on #2. Personally, I run
Apple VM on my 7.6.1 machine and do not notice a significant slowdown,
but then I do not push it very hard very often. This is very subjective,
and I do not have a rock solid opinion. In the early days of RAM Doubler
is was painfully obvious the RD outperformed old Apple VM, but we do not
see the obvious glaring discrepancy these days. In support of RD claims,
theoretically a slow disk may slow down Apple more than RD - but again
this is how, not what, and all that is important is the question "is it
faster on your machine", not "why is it faster"? Since no RD demo is provided,
nor are any benchmarks made available, we have no idea how you can evaluate
the performance.
3) Apple lets you set any value starting at 1 meg over real RAM
(the "1 meg over" limitation is arbitrary as far as we can tell), whereas
RAM Doubler 2 limits you to five fixed levels for absolutely no good reason.
RAM Doubler does allow you to set your memory to "File Mapping" which a
misleading label for "your real RAM amount", 1 meg less than Apple VM allows.
4) Cost. Free vs. Fee, you choose.
We run RAM Doubler on a Powerbook since it has a lot of RAM and limited
disk space, and since we care about battery life. We also run it on a few
other machines which are low on disk space, and on which we do testing,
but we don't know that we can tell the difference in performance between
RAM Doubler and Apple VM on these other machines.
But doesn't RAM Doubler add the new File Mapping functionality?
File Mapping is in no way a product of Connectix RD, nor a concept introduced
by RD, nor a feature exclusively available in RD. File mapping is an _aspect_
of virtual memory, provided on the Mac by both Apple and RAM Doubler (also
provided in Unix and probably most Window OS implementations). File mapping
provides "read-only" virtual memory, efficient since it never has to be
"swapped out" since it has backing store already on the disk (the mapped
file).
By our best guess, File Mapping was introduced in Mac OS approximately
OS 7.1.2, and may have always been supported by RAM Doubler - since it
arrived later. But hey, VM is not our domain so we are not absolutely sure
on the tame frame.
Running approximately OS 7.1.2 on a PowerMac, File Mapping is ONLY active
and is ALWAYS active when VM is enabled (Apple VM or RD VM) - regardless
of the "multiplier/amount" setting selected. (As far as we know File Mapping
is only available when running PowerPC - though it seems logical that a
68K code fragment could exist in the data fork of a file and be "File Mapped",
we have seen no proof that a 68K implementation of File Mapping was developed).
Connectix has taken great liberty with its labels and descriptions in
an effort to confuse the VM issue, and has obviously succeeded in this
case - leading some users to believe that File Mapping is a "Connectix"
product by using the "File Mapping Only" label in their control panel.
The "multiplier-slider" setting in RAM Doubler 2 is the direct equivalent
of the amount of memory you can set in the Memory Control panel under Virtual
Memory when virtual memory is "on" - though Apple provides more versatile
control, rather than a limited set of predefined "multipliers".
With "File Mapping Only" selected in RAM Doubler, RD doesn't multiply
the "total memory" amount, it just turns on [it's one and only form of]
VM. Thus, "File Mapping Only" is the logical equivalent of enabling Apple
VM with lowest possible multiplier/amount (1 meg over real RAM). The label
"File Mapping Only" does not mean VM is disabled, despite the literal interpretation.
VM is fully active. "File Mapping Only" is a misleading label whose real
meaning is better conveyed by the labels "Single", "None", or "no multiplier",
and running under the settings is functionally equivalent to running with
Apple VM enabled to the lowest possible amount.
Isn't RAM Doubler the same thing as RAM Charger?
No. RAM Doubler is virtual memory. Virtual Memory increases your memory,
but does not change the way it is distributed to applications. RAM Charger,
on the other hand, changes the way your memory is distributed to to applicitions,
but does not increase it. Details on the differences between RAM Charger
and vitutal memory are discussed on the page " What
REALLY different between RC & VM?", and the basics about VM are
covered on the page " Apple VM & RAM Doubler
VM (virtual memory)...".
Both RAM Charger and virtual memory (including RAM Doubler virtual memory)
may be used together on the same machine, and usually compliment each other.
Why is RAM Charger more complex the RAM Doubler?
This is a direct reflection of the unprecedented enhanced functionality
added by RAM Charger, and its inherent complexity. Since RAM Doubler does
the same thing as Apple Virtual Memory, which is intended to be a transparent
"memory substitute" for users, very little user interaction is required.
For marketing purposes, which proved successful, RAM Doubler added the
least possible new functionality beyond Apple VM (new features described
above). However, RAM Charger adds extensive control and feedback that was
previously unavailable for other aspects of application memory usage.
Compatibility with applications was also relatively assured for RAM
Doubler, while it was not for RAM Charger. Since virtual memory already
existed before RAM Doubler, most all applications were tested with VM and
related bugs were worked out - thus RD had very little trouble. The popularity
of RD encouraged any rogue applications to come in line with VM. Again,
note the Connectix comment here:
INCOMPATIBILITIES
WITH EXTENDED MEMORY
If RAM Doubler is installed, there are a few programs (usually
old ones)
that might see "extended memory" and assume that Apple's Virtual Memory
is in use, even if it is actually RAM Doubler that is providing the extended
memory.
If RAM Charger had been better understood, accepted and used in the
industry (or adopted by apple and integrated into the system by Apple)
then application developers would have been encouraged to test with it
and work out relevant bugs (which would just mean adhering to programming
standards documented by Apple). Moreover, we would have had greater revenue
to simplify our interface and would have had enough clout to encourage
developers to work with us (rather than the we don't care attitude of some
developers). As it was, RAM Doubler got a free ride on Apple VM's history,
and RAM Charger is on its own as a whole new thing.
It is also interesting to note the with Mac OS X, which now implements
the logical next step "RAM Charger style" dynamic memory model (already
commin on other OSes like Uinx and Windows), applications will have to
be re-written to take advantage of this new model - RAM Charger might have
helped prepare some application developers for this step.
Conclusion
We use RAM Doubler on some of our machines, and are pleased with the
results in many cases. However, Apple VM provides the same functionality
and it is only reasonable that people understand this. The only functional
differences between Apple VM and RD VM are reserved disk space usage, alleged
speed difference, and the size of memory you may specify.
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