Setting up the Horizon Ramdisk

The Horizon Ramdisk 4000 can be emulated via MESS/MAME. This selection will emulate a two megabyte ramdisk which 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 MAME1076b 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.