TRS-80 Model 4 IDE Drive Interface
The following document describes an IDE Drive Interface for the TRS-80 Model 4 and Larry Campanell's modifications for the LNW-80.
Features of the Model 4 interface are:
Things still to be done:
Building the Interface:
Interface Parts List
|DM74LS85N-ND||ZS-5085||U1 74LS85 4 Bit Magnitude Comparator||1|
|DM74LS04M-ND||ZS-5004||U3 74LS04 Hex Inverter||1|
|DM74LS27N-ND||ZS-5027||U2 74LS27 Triple 3 Input NOR Gate||1|
|P4849-ND||RC-5490||0.1uf Monolithic Capacitors||3|
|1.0XBK-ND||RR-0572||1K0 1/2W Metal Film Resistors||2|
|MHB40K-ND||PP-1114||40 Pin IDC Vertical Header||1|
|MHB50K-ND||PP-1115||50 Pin IDC Vertical Header||1|
Power Supply Parts List (not shown in schematic)
|ZV-1505||7805 +5v Fixed Regulator||1|
|P5183-ND||RE-6180||220uf 50v Electrolytic Capacitor||1|
|P5134-ND||RE-6066||10uf 16v Electrolytic Capacitor||1|
TRS-80 Bus Attachment Cable (not shown in schematic)
|C3AEG5018M-ND||PS-0990||50 Pin IDC Line Socket||1|
|50 Pin IDC Edge Connector||1|
|WM-4508||50 Way IDC Ribbon Cable||1|
Installing the Software:
Tim Mann for his great collection of Logical Systems Inc software.
Frank Durda IV for his LDOS Source Reconstruction Project and especially the hard disk driver source.
TRS-80 Model 1/LNW-80 IDE Drive Interface
The following describes Larry Campanell's modifications to the IDE Drive Interface for the TRS-80 Model 4 for use on the TRS-80 Model 1 and LWN-80. Larry has also provided drivers for DOSPLUS 3.5.
Some comment from Larry regarding the new interface....
"I did have to make a few changes to your hardware design because the Model I's expansion bus does not provide the /IORQ signal. I replaced U1 & U3 with a 74LS00 and 74LS32. The only other addition was to hang an LED on the IDE interface's /DASP signal to provide a "HDD Active" indicator."
"As for the software: I used your LDOS drivers as a guide but I created my driver and formatter for DOSPLUS ver 3.5 because I am more familiar with that OS. Refer to the attached zip file containing the driver (TRSIDE1D.SRC) and formatter (TRSIDE1F.SRC) source files, both in EDTASM format."
"I did have one problem, though -- not all IDE drives would work. Maybe I have a subtle hardware or software problem but, only one of the four IDE drives I tried would work. The working drive performs flawlessly leading me to believe the basic hardware & software design is good, however, the other three drives won't even pass the simple buffer read/write test I added to the driver's loader module.
The drive that works for me is:
Quantum ELS85AT 3.5" 80 Meg
The drives that wouldn't work are:
Western Digital WD2340 3.5" 340 Meg
Conner CP2081 2.5" 80 Meg (using a 2.5" to 3.5" adapter card)
Conner CP30204 3.5" 212 Meg
Anyway, Quantum the 80 Meg drive is more than enough for DOSPLUS 3.5 since it can only handle 8 drives (4 floppy, 4 hard) and each is limited to 200 tracks. Using a track offset of 200 for each DOSPLUS drive, I partitioned four 8 Meg drives and still have a 150+ tracks left over on the HDD.
I then created a boot floppy that will load the drivers and substitute the first HDD partition for drive 0 allowing the DOSPLUS system to run directly off the HDD. Wow, the computer really jumps. Type DIR and the files fly by on the screen. Programs seem to load instantly -- no more waiting for the floppy to chug along."
Download TRSIDE1Z.ZIP for Larry's driver and formatter source.
If you have any questions about the interface feel free to send me an email. My email address is email@example.com. I also keep a close watch on the comp.sys.tandy newsgroup under the JAQAS alias.
The LDOS 5.x drivers are on their way........ send me an email so I know you are hanging out for them and I can notify you when this site changes.
I am looking at the possibility of having some PCB's for the interface made if there is sufficient demand. If you are interested in a hard disk for your Model 4 and don't feel confident building the interface without a PCB or would like a built up PCB please send me an email and I will see how the numbers work out.
(C)opyright 2000, Andrew Quinn Last Updated 08 Feb 2001