Tandy TRS-80 model 4p

Under construction.

Front		Keys at reset: . Run RAM test V Print boot ROM version 1, F1 Hard Disk boot 2, F2 Floppy Disk boot 3, F3 Model III boot RIGHT-SHIFT RS-232 boot P Prompt disk switch at ROM-image load N Ignore OS request for ROM-image load L Force reload ROM-image BREAK Set flag at 405BH ENTER Terminate keyboard routine LEFT-SHIFT Reserved CTRL Reserved CAPS Reserved
Semi side

• Researching the KC-GIDE harddisk interface for the 4p.
• TRS-IDE vs GIDE driver
• TRS-80 cassette & disk images for the Model 1, III, 4 and 4p. Derived from the David Keil site via web.archive.org.
• TRS-80 Model III disk images from the TRS-80 archives
• TRS-80 Model IV disk images from the TRS-80 archives
• CP/M disk images from the TRS-80 archives
• Virtual library
• Commented boot ROM disassembly The comment is from Adam Rubin. It is edited to assemble correctly with z80pack/z80asm.
• Info on the serial boot option. Mainly from the Technial Reference manual.
• Hi-res images of the main board:component side and solder side.

The solution

Chromedome created an interface that actually works. See Cheapo-IDE-interface-for-Model-4p-running-MM-CP-M for more info on this interface.

First version of my TRS-IDE interface

Remember to reorient the IDE connector on the next board

Entered the following BASIC program (with a disk connected):

10 AD=63
20 X=10
30 OUT 236,16
40 FOR Y= 0 TO X
50 PRINT Y+AD;" ";INP(Y+AD)
60 NEXT Y

The result was:

63 255
64 0
65 1
66 1
67 1
68 0
69 0
70 80
71 80
72 1

The Seagate (ST3144A) doesn't work. Currently testing with a Conner (CP3008E).

Enter:

 SYSTEM (DRIVE=2, DRIVER="HDDVR6")

TRSIDE - IDE Disk Driver for LDOS 6.x/5.x
Enter drive select address <1-4>: 1
Enter total number of heads on drive <1-8>: 8
Enter physical tracks per surface: 22
Heads already in use <.-.-.-.-.-.-.-.>
Enter number of heads for partition <1-8>: 2
Enter starting head: 1

Now a blinking "H" should appear in the upper right side of the screen.

With some drives it does, but the drive is not addressed.

External IDE for 8-bit bus designs

• Model 4 IDE Hard Disk Interface TRS-IDE original site
• Another interesting IDE interface
• For the ZX-spectrum
• S100 bus design
• Boot ROM for the Model 4p
• uLabs Grafix board

Last update: 2022-03-20

fjkraan@electrickery.nl