HxCHARD FAT32/LBA - Emulated hard disk driver for HxC Floppy Emulator

Version 6.0.0b3+FreHD+Banks+Cache - Copyright (c) 2017, GmEsoft

Version 5.0.0b3+FreHD - Copyright (c) 2017, GmEsoft

Based on XTRSHARD/DCT - Copyright (c) 1998, Timothy Mann

Version 6.x of the driver is compatible with TRS-80 Model 4 running LS-DOS 6.3 and equipped with an HxC Floppy Emulator with an SD card formatted as FAT32/LBA.

Version 5.x of the driver is compatible with TRS-80 Models III and 4 running LDOS 5.3.

A VHD file must exist in the root directory of the SD card and must be named HARD4-n for version 6.x or HARD3-n for version 5.x where n is a digit in the range 0..7. This file is not expandable so its full capacity must be allocated. Two sample image files are provided: HARD4-1 for LS-DOS6 with a total capacity of 39 MB, and HARD3-1 for LDOS5 with a total capacity of 64 MB. They should be copied on the SD card without being fragmented because the current version of the driver cannot handle fragmented image files.

To load the driver, issue the following command at the DOS Ready prompt:

SYSTEM (DRIVE=m, DRIVER="HXCHARDx" [, ENABLE] [, SWAP=s] )

The driver then asks the following information:

Enter unit number (0-7)....................: n
Enter starting cylinder....................: sta
Enter cylinder count (0=default from VHD)..: cnt
Enter host drive I/O address (1-4).........: h
Enter memory bank (0-n)....................: b           [version 6.x only]

where:

x   = 3 for LDOS 5.3 "HXCHARD3", 4 for LS-DOS 6.3 "HXCHARD4";
n   = second digit of the VHD file name (HARD4-n/HARD3-n);
m   = logical drive number (:0 - :7);
sta = starting cylinder of the selected partition;
cnt = cylinder count of the selected partition;
h   = physical host drive number of the HxC Floppy Emulator.
b   = memory bank (0-0 for 64kB system, 0-2 for 128kB system, ...)
      where bank 0 is  the top half of  the main memory.

If b = 0, then HIGH$ is lowered by the amount of memory required by the driver.

If b > 0, then the DOS interface part of the driver must be loaded in low memory.

If b > 0, then LBA sector caching is enabled (27.5kB). Be sure to specify the same bank number for all instances of the driver, otherwise the system will become instable.

Currently the driver does not support HxC in dual floppy emulation mode (A+B).

The included disk image file HARD4-1 for LS-DOS6 contains 6 partitions of 140 cylinders each. The following script can be used to mount the 6 partitions:

system (drive=1,driver="HXCHARD4/DCT",enable)
1 [unit number]
0 [starting cyl]
140 [cyl count]
1 [host phys drive]
0
system (drive=2,driver="HXCHARD4/DCT",enable)
1
140
140
1
0
system (drive=3,driver="HXCHARD4/DCT",enable)
1
280
140
1
0
system (drive=4,driver="HXCHARD4/DCT",enable)
1
420
140
1
0
system (drive=5,driver="HXCHARD4/DCT",enable)
1
560
140
1
0
system (drive=6,driver="HXCHARD4/DCT",enable)
1
700
140
1
0

The included disk image file HARD3-1 for LDOS5 contains 6 partitions of 170 cylinders each. The following script can be used to mount the 6 partitions:

system (drive=1,driver="HXCHARD3/DCT",enable)
1 [unit number]
0 [starting cyl]
170 [cyl count]
1 [host phys drive]
system (drive=2,driver="HXCHARD3/DCT",enable)
1
170
170
1
system (drive=3,driver="HXCHARD3/DCT",enable)
1
340
170
1
system (drive=4,driver="HXCHARD3/DCT",enable)
1
510
170
1
system (drive=5,driver="HXCHARD3/DCT",enable)
1
680
170
1
system (drive=6,driver="HXCHARD3/DCT",enable)
1
850
170
1

1. This driver is not SYSGENable. Trying to SYSGEN after loading the driver will result in this error message:

   ** SYSGEN inhibited at this time **

2. The host physical drive must be mounted and enabled. The driver uses its DCT to store the current track number (255 in Direct Access mode).

3. The SD card must be formatted as FAT32/LBA, partition type 0x0C. Generally SDHC cards are already formatted as FAT32/LBA. If this is not the case, a tool like the free MiniTool Partition Wizard can be used to change the partition type of the SD card to FAT32/LBA (0x0C). The tool is available here:

   https://www.partitionwizard.com/

4. The VHD image file must be contiguous on the SD card, ie. unfragmented. This image file is not expandable, so the full capacity of the VHD must be allocated.

5. The hard disk emulation is done using the physical floppy disk controller. So the performance of the virtual hard disk will be limited by the performance of the controller. Moreover, data transfer with the image file is done by blocks of 512 bytes, corresponding to the sector size of the FAT32 file system. So, when an LS-DOS sector of 256 bytes is to be written on the SD-card, the target 512 bytes sector must be first read from the SD card, half of it is then updated and the sector is written back to the SD. This update is deferred for non-DIR sectors, but done immediately for DIR sectors.

6. The current version of the HxC firmware does not support sector interleaving in direct access mode. Based on that fact, we have empirically determined that the optimal number of data sectors on track 255 in Direct Access mode is 2 (so, track #255 presents the control/status sector followed by two 512 bytes data sectors). With a newer firmware supporting sector interleaving, the number of data sectors can possibly be raised to 8, hopefully with better performance.

7. From version 0.9 on, part of the driver can be loaded in extended memory. In order to allow this, the DOS interface part must be loaded in low memory, and a bank number greater than 0 must be specified. If a bank number > 0 is specified and there is no sufficient low memory space available to load the DOS interface, the driver will fail to load. When the driver is loaded into extended memory, some sectors transfers can be slower, if the sector buffer of the application is located above 7F00H, because a temporary buffer in low memory must be used between the application and the driver's 512 bytes SD sector buffer in extended memory.

8. From version 0.9 on, when driver is loaded in extended memory, LBA sector caching is enabled. The remaining space in the 32K extended memory bank after the driver is loaded is used to cache up to 55 512-bytes LBA sectors, ie. 27.5 kilobytes of cache memory.

9. From version 0.9 on, fragmented image files are detected and mounted read- only. If the driver detects a fragmented file, it will display the following message:

   WARNING: VHD file is fragmented; mounting read-only!

10. From versions 5.0.0/6.0.0 on, separate versions for LDOS 5 and LS-DOS 6. Version 5.0.0 for LDOS 5 is named HXCHARD3/DCT and currently has no support for extended memory (Model 4, above 64K) and no caching. Version 6.0.0 for LS-DOS 6 is named HXCHARD4/DCT.

• High memory is not available! - The driver can't be loaded either in low or in high memory.

• Must install via SYSTEM (DRIVE=,DRIVER=)! - The driver must be installed using the DOS command :

SYSTEM (DRIVE=n, DRIVER="HXCHARD")

and not directly as a /CMD program.

• DRIVE= must be specified! - The logical drive must be specified in the command:

SYSTEM (DRIVE=n, DRIVER="HXCHARD")

• Aborted! - BREAK was hit during initialization.

• No LS-DOS 6 - This version of the driver supports TRSDOS/LS-DOS 6.x only.

• Memory bank is not available! - The specified memory bank is either already used or inexistent.

• Can't load resident part in low memory! - The DOS interface part of the driver must be loaded in low memory if the specified memory bank is greater than 0.

Version 0.5 - preliminary test version - Mar 15, 2016

• First version delivered to test users.

Version 0.6 - preliminary test version - Mar 17, 2016

• drive selection (XDRIVE)

Version 0.7 - preliminary test version - Apr 19, 2016

• Fixed missing track register update in FDC I/O routines (0xF1)

Version 0.7a - preliminary test version - Apr 20, 2016

• Disabled SYSGEN

Version 0.8 - preliminary test version - Apr 25, 2016

• Support HD64180 by slowing down CPU during FDC I/O

Version 0.8a - unreleased - Apr 30, 2016

• Split driver in 2 parts:
  • DOS interface part, loadable in low memory
  • SD part, loadable in high memory

Version 0.9 - preliminary test version - May 07, 2016

• SD Driver loadable in 32K extended memory bank
• LBA Sector Caching when loaded in extended memory
• Reduced resident part size (smaller low memory requirement)

Version 0.9a - preliminary test version - May 08, 2016

• Better handling of fragmented files
• Fragmented files mounted read-only to avoid SD corruption
• Reduced resident part size; can now load EXMEM/CMD
• Resident module name is now "HxC"

Version 0.9b - beta version - May 14, 2016

• Fixed bug with buffer pointer HL destroyed on @WRSEC/@WRSSC when
• temporary buffer is used (if source buffer HL > 7F00H); appeared
• during backup operations.
• Limit bank number to 9.

Version 5.0.0b1/6.0.0b1 - beta version - May 24, 2016

• First version for LDOS 5.3: version 5.0.0b1 without EXMEM support and without cache (version for LS-DOS 6.3 is 6.0.0b1)
• Optimized Direct Access Mode activation
• Fixed bug with DCT pointers table
• Version 5.x.x is for LDOS 5 and is named HXCHARD3/DCT
• Version 6.x.x is for LS-DOS 6 and is named HXCHARD4/DCT

Version 5.0.0b2/6.0.0b2 - beta version - Jun 5, 2016

• Fixed bug in sector caching handler (bad status on exit)
• Restore XLR8er speed after entering Direct Access Mode
• New HxC2001 HiRes Logo (overlay mode for Micro-Labs Grafyx boards)

Version 5.0.0b3/6.0.0b3 - beta version - Jul 26, 2017

• Direct Access Mode I/O: when I/O fails, force Direct Access Mode and try again.
• When wrong host drive is specified, error message changed from x'05' (data record not found during read) to x'32' (illegal drive number).

HXCHARD/DCT is freeware, but remember that it is not public domain software. All copyrights connected with the program and its accompanying document files remain with me (Michel Bernard).

Any feature request or defect report can be sent to me at the following e-mail address:

mailto:[email protected]

The softwares included in the provided VHD image are copyrighted by their respective authors. This VHD image is freely downloadable from the web page:

https://ianmav.customer.netspace.net.au/hires/M4FreHDHRG.zip

The HxC Floppy Emulator is a piece of hardware that can emulate 1 or 2 floppy drives using image files stored into an SD or SDHC card. More information about the design of this device on the HxC2001 site:

https://hxc2001.com/

The HxC Floppy Emulator is built and sold by Lotharek and can be ordered here:

https://www.lotharek.pl/category.php?kid=7

HxCHARD/DCT would not have been possible without the contribution of the following people:

Jean-Francois Del Nero who designed that fantastic piece of hardware, the HxC Floppy Emulator.

Przemyslaw "Lotharek" Krawczyk from Poland, who builds and sells HxC Floppy Emulators.

Tim Mann from California, who developed XTRSHARD/DCT on which HxCHARD/DCT is based.

Gazza from "Downunder" and Martin Lucas from Texas who spent considerable time to test and help me in debugging the driver.

Ian Mavric from Australia, who builds and sells FreHD Hard Disk emulators and publishes some VHD images on his web site.

Raymond Whitehurst from Australia who introduced HxCHARD to his friends, including Gazza and Ian Mavric.

Many thanks to all of them for keeping the TRS-80 alive !