From: markus@techfak.uni-bielefeld.de (Markus Illenseer)
Subject: Virtual Memory, a first test.
Date: Tue, 28 Jul 92 10:14:48 GMT
Organization: Universitaet Bielefeld, Technische Fakultaet.
Keywords: VMEM


	Hello Net-Land !

As promised hereby a first small report fo testing for the VMEM avail for
Amiga Systems.
It's known under the name 'GigaMem', was programmed by the Relog 
AG/Switzerland, thereby written by Christian A. Schneider, Friedeman 
Buergel and others.
'GigaMem' is distributed by BSC/Germany. 
(This should be enof advertisement, from now on we call it VMEM :-)

Of course, i asked myself why i should need VMEM. Just one word:
A26x0. This and other Turbo-Card can only be upgraded upto 4 MB.
I myself do image processing and need much memory for working with large
pictures. So i really would like to have more than 9 MB RAM, which is my 
current limit. So i consider VMEM as a real Alternative to those expensive
Add-On Cards.

For VMEM an Amiga with MMU is required, most Turbo-Cards with 68020 or 68030
do have such a MMU. A 68040 is not yet supported. Also a hard drive with
some empty space is required. The faster the better, the more DMA the 
better the swap :-)

VMEM was tested on my Amiga A2000 with A2630/25/4, A2091 (SCSI), 4 MB 16 Bit 
RAM-Card (total 9 MB real RAM) and on an A3000/25 with 10 MB RAM.
As harddrives we used several SCSI-Drives, such as Quantum LPS105, Q80S and
a Syquest SQ550 (removable) and a DEC DSP5200S. The last drive was borrowed
from Max Planck Institute for Radioastronomie, it's a 1.9 GB Drive.
(Thanks to Michael and Petra!)

As OS only OS 2.04 was used (both, my A200 and the A3000 do have 2.0 ROM's),
accordingly the manual VMEM also runs under WB 1.3, couldn't be tested though.

The manual is bilingual, english and german. The english part was written
by the authos themselves, the german part was translated by BSC.
On 50 pages (each part) the functions of VMEM and it's accompnied tools
are nicely describen. Very accurate and short but understandable.
I missed some hints on the use of the real Memory. Duing the test, VMEM
was somewhat (real) RAM-greedy, i explained that due to the fact that a 
MMU-Table for a large VMEM-Partitions can be large, too. This is not mentioned.
Ok, it's not common to have 1.9 GB VMEM, for smaller Swap-parts the MMU-table
is far smaller, too, of course. The manual states that VMEM runs with upto
1 GB space, i thionk the authors didn;t had access to a larger drive, 
VMEM runs fine with 1.9 GB :)
Also i missed hints for possible dangers or problems, e.g. that VMEM doesn't
run with 'CPU FASTROM' (needs MMU table itself).

The installation was very simple, the 'new' Installer from Commodore is used
to install the library, the Preference-Tool and the main-programm. 

Under OS 2.0 the mainpart is installed in Sys:wbstartup. 
The Preference Tool is very well done. It provides possibilities to add 
VMEM to a (or several) specific programms. On startup-default well known
programms such as ADpro, ImageMaster Ced and many more.
Others can be easily installed.
VMEM provides to ways to swap onto a hard drive: Partitions or files.
The first way is faster and somewhat better. The second is a bit slower and
more interesting when VMEM is used less often. So hat you can even delete
the swap-file. 
So any programm can have VMEM in a spcific way, e.g. allocate 20 MB for ADPro
and tell ADPro not to use any real-RAM, tell Ced to use VMEM first then Real-
Mem , and so on.
A global VMEM , such as the vmem of the Evolution-SCSI-adapter, is not 
provided, one may discuss this, i think the way VMEM does it is better.

We had many ideas to make VMEM go hot, it was quite hard, we had no luck to
crash it really to dead. Of course we can provocate a crash, but this was not 
our intention, we want to use VMEM of course.

Not every programm actually work with VMEM. Multitasking is one side, clean
code the other. Some program never ever need VMEM, other cries for it.

As first program ADpro, this old MemEater was tested. The company ASDG told
me on the AmiShow in Cologne (last year) that a real Power-User only works 
with Real-RAM, ok, but how much is 64 MB RAM at the time ? At least ADPro
denied to work with more than 512 MB VRAM ! (At least with my borrowed version)
Some pictures were enhanced to monsters like 12800 * 9600, displayed, and
re-rendered with some of those morphologic filters. This takes time but
it did work.

The direkt concurent Imagemaster had no problem to run with 1.9 GB, due to
time reasons we decided just to resize a picture to a picture-Monster and
do a filter operation.

The Pbmplus-libray , also know as MemEater, had no problems at all, though
it works with pipes and redirections on the RAM:-Disk.

Good old DPaint likes to work with VMEM, but it;s only usefull for Animations,
as it needs Chip-Ram for the bitplanes.

Ced had no problems to replace 'a' to 'e' in a 100 MB File.

As i am not a music-freak, i had no intention to test VMEM with a Soundtracker
or Digitiser.


Of course VMEM works with smaller hard drives, e.g. my Syquest, but this one is
solow and makes noise :) 

All in all VMEM was very stable and simple to deal with. The only problem
which did acutally occure was a problem with a 'MAsk'-entry in the Mountlist.
This was ou only crash in about 10 hours testing.
For large VMEM partitions, you need large MMU Tables, therefore the real RAM 
decreases. Using 'normal' swapp-sizes this causes no problems at all.

Due to the nature of VMEM you need somewaht time during swapping, but this
is understandable.

Total: I can't miss it anymore. As i am on the hardware-limit, VMEM is a 
nice alternative to those expensive Ram-Cards. And, you can limit the RAM
use.

Have fun, Markus.

PS. The price is 198.- DM,   ALF-3 users get update (limited to ALF-devices!)
PPS. I am not related to BSC, but i know the authors personally :)
PPPS. I am on holiday the next 3 weeks, don't mail me :)


-- 
Markus Illenseer       EMail: markus@TechFak.Uni-Bielefeld.de
Universitaet Bielefeld Fax: (+49 521) 106-2992
Technische Fakultaet   Phone: (+49 521) 106-2926(internal only); -5329
Angewandte Informatik  SnailMail: Postfach 100131, D-4800 BIELEFELD 1