[Search for users] [Overall Top Noters] [List of all Conferences] [Download this site]

Conference hydra::amiga_v1

Title:	AMIGA NOTES
Notice:	Join us in the NEW conference - HYDRA::AMIGA_V2
Moderator:	HYDRA::MOORE

Created:	Sat Apr 26 1986
Last Modified:	Wed Feb 05 1992
Last Successful Update:	Fri Jun 06 1997
Number of topics:	5378
Total number of notes:	38326

326.0. "Beware of AddBuffers" by LEDS::ACCIARDI () Sat Feb 14 1987 21:38

    While playing around with the DOS 'AddBuffers' command today, I
    noticed that the memory allocated is stolen from CHIP memory, even
    when FAST memory is available.  You might want to consider this
    when running multiple graphics-intensive programs, i.e Aegis Draw
    and PageSetter.  
    
    On the plus side, I did not notice any appreciable speed difference
    between allocating 25 512 byte buffers or 100 buffers, so there
    doesn't seem to be any great reason to waste valuable CHIP memory,
    anyway.

T.R Title User Personal
Name Date Lines

326.1 Floppies can only address chip memory TLE::RMEYERS Randy Meyers Mon Feb 16 1987 11:45 26

T.R	Title	User	Personal Name	Date	Lines
326.1	Floppies can only address chip memory	TLE::RMEYERS	Randy Meyers	`Mon Feb 16 1987 11:45`	26
	Re: .0 The memory comes from chip memory because the DMA channel for the floppies can only address chip memory. Furthermore, once the data is in memory, the blitter is used to decode the data from its encoded form into its true form. Note that not all DMA channels have to use chip memory. A hard disk manufacturer can (and is encouraged to) build a disk interface that does DMA into fast memory. One of the options in the "Mountlist" description of a device is whether the buffers for the device should be placed in chip or fast memory. The blitter is used for the format decoding because it is a general purpose, high speed boolean operation engine--it does a lot more than block moves. That is why Jay Miner, the chip's designer, calls it a "bimmer," for bit-mapped image manipulator. Calling the chip a blitter is a little bit like calling a top of the line, programmable HP calculator an "adding machine." Since I have a 2.5 meg Amiga, I usually run with AddBuffers 100 for both my floppy drives. I have noticed a great deal of speed up when doing repeated DIRs of directories with large numbers of files. Since I seem to have a great deal of chip memory to spare, the AddBuffers seem like a good idea. As .0 points out, if you do lots of animation or sound digitizing, you may want to skip the AddBuffers.

Re: .0

The memory comes from chip memory because the DMA channel for the floppies
can only address chip memory.  Furthermore, once the data is in memory, the
blitter is used to decode the data from its encoded form into its true
form.

Note that not all DMA channels have to use chip memory.  A hard disk
manufacturer can (and is encouraged to) build a disk interface that
does DMA into fast memory.  One of the options in the "Mountlist"
description of a device is whether the buffers for the device should
be placed in chip or fast memory.

The blitter is used for the format decoding because it is a general
purpose, high speed boolean operation engine--it does a lot more than
block moves.  That is why Jay Miner, the chip's designer, calls it a
"bimmer," for bit-mapped image manipulator.  Calling the chip a blitter
is a little bit like calling a top of the line, programmable HP calculator
an "adding machine."

Since I have a 2.5 meg Amiga, I usually run with AddBuffers 100 for both
my floppy drives.  I have noticed a great deal of speed up when doing
repeated DIRs of directories with large numbers of files.  Since I seem
to have a great deal of chip memory to spare, the AddBuffers seem like
a good idea.  As .0 points out, if you do lots of animation or sound
digitizing, you may want to skip the AddBuffers.