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1992-08-27
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Busmastering Controllers
────────────────────────
To optimize performance, busmastering controllers bypass the system board
DMA controller and perform their own DMA transfers. Typically these
devices tend to be SCSI fixed disk controllers. With a memory manager
installed, however, it is possible for memory to be remapped and not retain
a one-to-one linear to physical relationship. To ensure that DMA transfers
are properly performed in memory which is not mapped one-to-one, a
busmastering device must use one of two schemes: double buffering, or VDS
support.
During initialization, 386MAX displays an error message if it detects a
busmastering hard disk controller that is not VDS compatible. In order for
386MAX to detect a busmastering controller, either high DOS memory or an
EMS page frame must be present. If a busmastering device does not support
VDS, then one must obtain an updated BIOS for the controller or a software
driver which supports either VDS or double buffering from the vendor. VDS
drivers can be loaded after 386MAX.SYS in CONFIG.SYS and may be loaded into
high DOS memory. If the driver provides double buffering, it must be
loaded before 386MAX.SYS and must be loaded into low memory. To bypass the
386MAX.SYS busmaster error message at startup, add the keyword NOSCSI to
the 386MAX.PRO file.
Some disk caches implement double buffering schemes (QCache or SMARTDrive).
If you are using a cache which double buffers disk transfers, do not load
the cache into high DOS memory (QCache is loaded high automatically, and
SMARTDrive 4.0 may be loaded high with 386LOAD. See QCACHE.DOC for more
details). Doing so may cause the disk cache buffer to be loaded into
memory that is not mapped one-to-one, resulting in data loss.
If MAX.SYS has detected an unsupported busmastering controller and
SMARTDrive is not loaded, an error message will result when loading Windows
3.0. If you are SURE you have a VDS-compatible busmastering controller,
place SET BUSMASTER=VDS in your AUTOEXEC.BAT to bypass this error message
and load Windows 3.0. Note that using these options without regard or
knowledge of your system setup can result in loss of data. Also, when
using a SCSI device and running Windows 3.0, the user should add the option
VirtualHDIRQ=FALSE to the SYSTEM.INI file in the Windows subdirectory.
Contact your hard disk controller manufacturer for detailed information
about your hard disk controller. To ensure that the following busmastering
controllers perform properly, follow the listed steps for each:
Adaptec
───────
If you are using an Adaptec 1542, Adaptec ships a software driver called
ASPI4DOS.SYS that must load in your CONFIG.SYS before 386MAX.SYS.
Storage Dimension
─────────────────
Storage Dimension SCSI drives use a 16KB RAM buffer area in high DOS
memory. Protect the appropriate 16KB address area with a RAM= option in
the 386MAX.PRO file. The default addresses are C800-CC00 or CC00-D000.
Therefore, add the statement RAM=C800-CC00 or RAM=CC00-D000 to the
386MAX.PRO file.
Western Digital FASST SCSI
──────────────────────────
This controller ships with two software drivers called FIXMEM.SYS and
SSTBIOS.SYS. Copy these device drivers to your boot disk. Insert the
separate lines DEVICE=d:\path\fixmem.sys and DEVICE=d:\path\SSTBIOS.SYS /WE
to your CONFIG.SYS file preceding the 386MAX.SYS line. VDS support is
incorporated into ROM revision 3.36 or later.
Other Hard Drives and Controllers
─────────────────────────────────
Seagate ST01 & ST02
───────────────────
These controllers use a 32KB RAM buffer area in high DOS memory. Protect
the appropriate 32KB address with a RAM= option in the 386MAX.PRO file.
The default RAM= option is C800-D000, but the controller can optionally be
located at D800-E000.
Storage Dynamics D1008
──────────────────────
This SCSI is not a busmaster, but does use a 16KB RAM buffer at C800-CC00,
CC00-D000, D000-D400, or D800-DC00. Use a RAM= statement with the
appropriate address range.
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Qualitas, Inc. Main : (301) 907-6700
7101 Wisconsin Avenue Sales : (800) 733-1377
Suite 1386 FAX : (301) 907-0905
Bethesda, MD 20814-4805 BBS : (301) 907-8030
CompuServe : 73377,3307
MCI Mail : 336-2907
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386MAX, BlueMAX, and MOVE'EM are trademarks of Qualitas, Inc.
All company names and products are trademarks or registered trademarks
of their respective companies.