Setting up the Horizon Ramdisk

Horizon Ramdisk

   This emulation realizes the latest development, the HRD 4000, which could
   host up to 16 MiB of SRAM. Real cards rarely had more than 1.5 MiB since
   the SRAM used on the card is rather expensive.

The Horizon Ramdisk 4000 can be emulated within MESS/MAME 2MiB of SRAM! The data that is stored on the RAM Disk is actually saved in the "\nvram\ti99_4a" directory within a file.

Note: The directory is usually classified by the current machine type being emulated

The emulation will respond to the equivalent speed of the ram disk on actual hardware.

This process was created using MAME0176b 64bit and ROS version 8.32e.

Note: If using ROS 8.14f or earlier, sector sizes will be limited to 1600. ROS 8.32 allows for 3200 sectors per disk.

Procedure:

1> Boot into MAME and the TI-99/4A ROM 

2> Bring up the MAME menu by pressing SCROLL LOCK then press TAB

3> Configure your System Devices for your wanted configuration.  For this example I will be showing PEB Slot #5 as the Horizon RAMDISK.

4. Reset the machine for the settings to go into effect.

The default CRU address for the ramdisk is 1200. If there will be multiple HRD's then the CRU address will need to be changed for each additional HRD to a CRU that does not conflict with any other expansion card.
5. Bring up the MAME menu by pressing SCROLL LOCK then press TAB
6. Select Dip Switches

7. Select the Horizon ram disk slot
8. Select Horizon CRU base option and change the CRU appropriately

You will need to do this for each ramdisk within the system if you have more than one.
9. Reset the machine for the settings to go into effect.
10. Bring up the MAME menu by pressing SCROLL LOCK then press TAB
11. Select File Manager to select cartridge and disk images.

12. Mount the ROS disk image

13. Select Cartridge to load Extended Basic

14. Press ESCAPE twice to exit the MAME menu
15. Press SCROLL LOCK to disable the MAME menu
16. Press ANY KEY to go to TI-99/4A menu
17. Press 2 to go into Extended Basic and the HRD ROS Loader should load.

18. Select 1 for CONFIG Loader/Editor

The ROS CONFIG will detect the currently installed expansion cards. The below image shows two Horizon Ramdisks.


19. Press ANY KEY to start configuration
20. Press L to load configuration file
Note: Select appropriate configuration file for the disk controller installed into the system (Myarc/TI/CorComp)


21. Press E to edit configuration
22. Keep all defaults but change Power Up to N (NO)

To cycle through selections press ENTER; FCTN-9 when done (ALT+9 in MAME)


23. Press D to configure RAMDISK drive assignments and sizes

Note: Use cusor keys to move different disk drive numbers

24. Select Disk Drive # to assign
25. Assign a Disk Name of the disk (based on TI Disk Naming criteria)
26. Select N for No Write Protection
27. Select Y to format the drive
28. Select sector size

Note:
1600 max sector size for ROS versions earlier than 8.32
3200 sectors size for version 8.32+
Drives can be denfined from DSK1-DSK9 and DSKA-DSKZ



29. Press FCTN-9 when done (ALT+9 in MAME)


If there is more than one Horizon Ram Disk installed then hit N for next to configure the next HRD.

Note: The ROS does not verify selected Disk Drive numbers/letters that are already in use. The user will need to keep track of what is in use.


Now the HRD should be accessible.