vb2091 (vbak2091) V1.5 (19.12.2007)
(c) in 1994 by Volker Barthelmann,
modified 1996-97 by Andreas R. Kleinert,
re-uploaded 2007 with updated documentation.
USAGE AT YOUR OWN RISK. NOBODY CAN BE HELD RESPONSIBLE FOR ANY DAMAGES.
THERE IS NO FUNCTIONAL CHANGE IN THIS RELEASE - THE MAIN REASON TO MAKE
AN UPDATE AGAIN AFTER 10 YEARS WAS TO EMPHASIZE AGAIN THAT ALL A2091
ROMS FROM COMMODORE ARE SEVERELY BROKEN AND THAT IT DOES _NOT_ MAKE
SENSE TO RUN AN A2091 IN AN A4000 WITHOUT GURU-ROM.
This is a slightly reworked version of vb2091 by Volker
When running vbak2091 it may make sense to install
the following programs (in this order), too:
C:FastExec NOEXEC FASTSSP FASTVBR FASTEXP FASTMEM FASTINT
C:LoadV43Module c:a1000.ld.strip REBOOT
Run C:MapBoard A2091
Run C:vbak2091 [OPTIONS]
C:NSDPatch PCF DEVS:NSDPatch.cfg QUIET
Note the following:
- all programs should be called as "[command] >NIL: <NIL:"
or "Run >NIL: <NIL: [command]" (has been shortened above).
- FastExec is recommended (Aminet).
- LoadV43Module (and the scsi.device V43 patch strip) can
be found on ftp.amiga.de (Beta).
- SetPatch V43 is recommended. Can be found on ftp.amiga.de
- you have to supply additional options for "vbak2091" (see
- MapBoard can be found on Aminet. It will drastically
the speed that can be reached in conjunction with vbak2091
- NSDPatch turns the old A2091 scsi.device V37.x into a 'new
device and thus should be installed *after* vbak2091.
Can be found on ftp.amiga.de (Unsupported).
- you may also wish to install the newest FastFileSystem V43
version on the related hard disk partitions.
Can be found on ftp.amiga.de (Beta)
The above configuration basically worked for me - you have to
test for yourself whether the newest versions of the concerned
tools will work as well with your system configuration.
Included you find the compiled SAS/C version (vbak2091),
the SAS/C, GCC and VBCC-aware source code (vbak2091.c)
and the original source code of the last public Aminet
So you can easily see, what the program is doing.
Feel free to modify and improve the source code,
but tell us before releasing it !
Neither me nor Volker will take any responsibility
for any results out of the usage of this program;
neither for any damages nor any loss of data, nor
anything else. It's your own risk!
Following is the original documentation (note, that
the remark on ixemul.library is obsolete - see also
ZorroII boards can only reach the lower 16MB of address space. So DMA
SCSI controllers must find another way to transfer data to expansion
RAM. Some of them (especially the A2091) do a very bad job in this
situation. In an A4000/40 transfer rates may drop to 50KB/s.
This program patches the (2nd.)scsi.device to use MEMF_24BITDMA
RAM as a buffer followed (in case of CMD_READ) by CopyMem().
It was developed with the A4000/A2091 combinbation in mind, but
should work with other configurations, too (see REQUIREMENTS). Some
people reported good results with GVP controllers.
There have been some bugfixes, additional options and changes of the
commandline options since the last public release. So I am afraid all
users of previous versions will have to read this manual again
(especially the USAGE section).
There are already some PD utilities floating around that do a similar
job. So why may this one be better?
- It patches the device instead of the Read() & Write() DOS-functions,
giving the following advantages:
o Programs accessing the device directly (e.g. SysInfo, SCSI-Speed
or tape-handlers) are patched, too.
o Patching Read() doesn't seem to have any influence on LoadSeg(), so
those patches don't speedup loading of programs whereas vb2091 does.
o It is possible to use double-buffering and load into one buffer
while copying the contents of the other one to fastram. This makes
higher transfer rates possible. I wasn't able to get more than
800KB/s with DOS-level-patches, but could get over 1MB/s with
- Some early A4000s (including mine :-( ) can't do DMA to onboard ram.
On such A4000s every transfer to/from chipmem will cause the
computer to hang. vb2091 can be told to redirect those transfers too.
FIRST: READ THIS ENTIRE FILE BEFORE TRYING OUT vb2091 !!
(This is meant seriously - I know this is a very badly written manual,
but it mentions some very important points.)
This program is still beta and I can't give any warranty about anything.
I have tested it for some time and have not encountered serious
problems, but had no opportunity to test vb2091 on other configs,
so there may still be many bugs.
It seems to work fine with my system (A4000/40, broken DMA, A2091/7.0
ROMs, Quantum LPS270S+LT730, Tandberg streamer) in conjunction with
MapBoard, however there may be problems with the serial port.
vb2091 has been compiled with gcc, so it needs ixemul.library in libs:
and ENV: assigned. Keep this in mind when placing it in Your startup-
sequence. There will probably be a version that has been compiled with SAS
in this distribution. This version doesn't have these requirements.
As it uses the exec-functions CopyMem()/CacheControl(), it doesn't work
with early versions of Kickstart (sorry, I don't know since when these
functions are present - probably since 2.0).
vb2091 does not check for a correct version at the moment (sorry).
You must have some MEMF_24BITDMA RAM (e.g. RAM on the controller or
chipmem) to be used as a buffer.
I hope I haven't forgotten anything (of course a controller and some
expansion RAM would be quite useful).
[run] vb2091 UNIT <unitlist> [DEVICE <device>] [BUFSIZE <bufsize>]
[MAXN <number>] [MIN1BUF <size>] [MIN2BUF <size>]
[BROKEN] [SINGLE] [NOCACHE] [NOWRITE]
All the keywords must be uppercase! (sorry)
UNIT List of unitnumbers of devices to be patched, not separated by
spaces or commas, e.g. 014 for device 0, 1 and 4.
(default: no default - this MUST be specified)
DEVICE Name of the device to be patched.
BUFSIZE Size of buffer in kilobytes.
BROKEN Use this if You have got an A4000 that cannot DMA the chipmem.
You MUST have some 24Bit fastmem (e.g. on the controller)
then - vb2091 will only accept MEMF_FAST|MEMF_24BITDMA RAM
as buffer then.
SINGLE Normally vb2091 uses double-buffering to get slightly higher
transfer rates; use SINGLE, if free processor time is more
important to You. Currently only CMD_READ is double-buffered,
CMD_WRITE is not.
NOWRITE If You specify this option, only CMD_READ ist patched, whereas
CMD_WRITE will be unchanged. Use this if You don't trust
NOCACHE If this option is specified, the DataCache will be disabled
before CopyMem() and enabled after finishing; this will speedup
CopyMem() (at least on a 040). This has not been tested very
well, so be careful with this option.
MAXN <number> (default: 16)
MIN1BUF <size in kilobytes> (default: 128)
MIN2BUF <size in kilobytes> (default: 64)
These options can be used to adjust some parameters which are
used with double buffering. If a block of size l is to be read
then vb2091 will probably split the transfer into smaller blocks
for better use of double buffering. If l<MIN1BUF then vb2091
will use one transfer of l bytes (i.e. no double buffering), if
possible. If l>MAXN*MIN2BUF then the transfer will be split into
MAXN parts. If none of those conditions is true then the transfer
will be split into blocks of size MIN2BUF.
I thought about a rather simple method to let the user adjust the
buffers in different situations without having to specify one
BUFSIZE for almost every single transfer size. The method I used is
just heuristic and the default values were chosen rather arbitrary
and optimal values may be quite different (especially on different
systems). MIN2BUF shall be set to the smallest size which achieves
good transfer speeds with little cpu usage. So MIN2BUF is the value
which should usually be used as buffer size (yielding high rates
and as many chunks, i.e. best use of double buffering, as possible).
But if the transfer size is a little larger than MIN2BUF, it
wouldn't be a good idea to usee double buffering with those chunks.
E.g. with MIN2BUF=64k a 65k transfer would be split up in a 64k
transfer and a 1k transfer. Although I haven't tested it, one 65k
transfer should be better. Because of this You can prevent double
buffering for any transfers less than MIN1BUF. I set
MIN1BUF=2*MIN2BUF for default, but this may be too large.
Now if You have very large transfers (e.g. 4MB), then it would be
split up into 64 64k chunks. But from a certain number of chunks it
should be better not to raise the number of chunks but the size of
the chunks (especially as MIN2BUF should be set as small as
possible). This is what MAXN is for - however this is rather
theoretical, because I doubt that transfers that large will occur
often (if at all).
As said before this method can be argued (especially as I almost
haven't tested if my thoughts are true in reality) and the default
values may be far from optimal. So everybody who wants almost
optimal performance has to find out his personal values (they also
depend on the applications You use, because You can configure
vb2091 for best speed or least cpu usage or something inbetween).
run >NIL: vb2091 DEVICE scsi.device BUFSIZE 128 MAXN 8 UNIT 046
You can remove the patch by sending vb2091 a CTRL-C/break - but don't
do this while any program is using the device.
I decided to distribute the source in order to raise chances of finding
bugs. You should be able to compile it using gcc (I used 2.3.3) or SAS.
It is NOT meant to be an example of good programming and I am not liable
for anyone turning into stone after looking at it.
This program would not exist without the help of Olaf Seibert (another
poor fellow with a broken A4000) who encouraged me to write it and
provided me with helpful information. Thank You, Olaf!
Thomas Boerkel did the changes for SAS and compiled it.
Several testers helped to remove some bugs of the older versions and made
suggestions for improvement.
vb2091 may be freely distributed as long as no part of the distribution
This program is Bearware: If You like it, You can send me something
with a bear on it.
But more important:
If You try it, please send me Your experiences, bugreports,
I should be reachable per eMail via: