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Zenith Z-171 Z-170 ZFL-171-42 : XT-CF card

T

Twospruces

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Dec 9, 2009
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So I started a project to create an XT-CF card based on the Lo-tech design a month ago.
Making some progress.
First major issue was that the "standard" ISA port on the Z170 is not well documented (in the user manual and the service manual)
* it is wired backwards relative to the standard port, so my layout was a mirror image of what was needed
* power pins are not correctly documented

Despite those setbacks I have now got a flashable card installed in my Z171.
I'm now debugging the specifics of the actual bios used, the settings, getting an FDISK.COM that works and recognizes the HDD etc etc.
 
I'd be interested in seeing your schematics and slot documentation if you share them. I had to do (probably similar) adaptations for the cards I've been making for the "PLUS" bus in my Tandy 1000 EX, which is likewise ISA-but-*not quite* on a different connector.
 
I've been able to get something working reasonably well, with caveats.

* while it is possible to use DOS newer than 3.1, newer DOS tends to not work great with the floppy drives in the Z171. Recommend sticking with stock Zenith 3.1 MSDOS.
* start up of the machine suffers from a defect which may or may not be resolved. Basically, to boot up or reset the machine you must power down for 10 seconds, boot once, soft reset before boot attempts to read from CF card, and then let the next boot proceed. It is a bit clumsy but manageable.
* I'm using R602 XUB firmware

The ISA socket is wired up mirrored relative to the standard card. This means I need new PCBs.

I'll have to post the PCBs with instructions at Oshpark when the next boards are verified.
 
Twospruces said:
Sure happy to.
Does that computer have an isa slot internally?
Click to expand...

Not a standard slot, no. It has a 20 pin and a 26 pin connector which normally has a sub-card plugged in which the JVC HDD attaches to. I presume that it is a HDD controller card that communicates via what is essentially a custom-connected ISA slot or slots; I'm working on getting a wiring diagram for the connectors.

What would be most helpful is any sort of documentation you have from the slot back to chips on the board.
 
Didn't realize the ZFL-171 could have a hard drive though I was hoping someone would design a flash adapter for the partial ISA bus sticking out the back?

Mine is a ZFL-171-82 (dunno what the 82 means but i think it is a fully upgraded model). Edit this was a computer reset find.. it was located in a filing cabinet in the laptop room. I saw at least one more on the stairs while I was there.

https://www.facebook.com/chase.rayfield/videos/10156390621107108/
 
Yes that is the point of this project. Compact flash "HDD" . Its working well with some simple rules for how to power up and reset. I have a new pcb to test out due to the reversed pinout of the connector. Saw you changed to NEC V20. Is that a VMOS CPU?
 
Yah thanks. Checked that datasheet and it is 10mA per MHz like the 80C85...so seems like a good upgrade.
 
Here is the primary side of the new PCB for this thing.
Capture.jpg

The idea is that when it is installed (BTW - the RGB Video board can't also be installed!) in the main board connector, it is flush with the case. When the CF card is inserted, the Card itself will protrude out the back of the case so you can easily insert and extract the card.

My Z171 has a travel case; one would need to remove the CF card in order for it not to snag on the cloth of the travel case.

More pics as I build it up.
 
I am pleased to report that I have repaired XUB to work with Z-171. Well, specifically I fixed the boot disk detection problem that was making boot up difficult.

Here's the short summary of the issue:

* in Z171, when booting a stock machine, the BIOS BDA entry 0040:0075, which represents # of detected HDD, is set to 0FF.
* (It also seems like it is not initialized on normal boot up, so FF might be what you get when power up)
* XUB assumes this value is correctly set by the BIOS.
* in the case of Z171, it should be set to 00 on every boot

Fix:
* in DetectDrives.asm there is a natural location to initialize the variable BDA..bHDCount which points to 0040:0075
* by initializing to 00 we correct the problem that un-initialized data is messing up the boot
* in the make file you need to add this line to the appropriate area
# Z171_HACK use to fix Z171 boot issue
* and of course, you need to add this to your specific build.

original code

mov cx, [RAMVARS.wDrvCntAndFlopCnt] ; Our count of hard disks
mov al, [es:BDA.bHDCount]
add [es:BDA.bHDCount], cl ; Add our drives to the system count
or al, 80h ; Or in hard disk flag
mov [RAMVARS.bFirstDrv], al ; Store first drive number


modified code


%ifdef Z171_HACK ; INITIALIZE .bHDCount every time
mov BYTE [es:BDA.bHDCount], 0 ; Set hard disk count to zero
%endif ; Z171_HACK

mov cx, [RAMVARS.wDrvCntAndFlopCnt] ; Our count of hard disks
mov al, [es:BDA.bHDCount]
add [es:BDA.bHDCount], cl ; Add our drives to the system count
or al, 80h ; Or in hard disk flag
mov [RAMVARS.bFirstDrv], al ; Store first drive number
 
Here are some pics of the final version for those who might be interested. Big thanks to Lo-Tech for sharing schematic and the XUB team for the firmware. PM me if you are interested in having one of these.

In the pics below you will see a black wire that loops around. that is there to help me pull out the board once it is installed. Not really needed, but when I was debugging things I did need to extract it. As you can see, the board is flush with the back of the PC and only the CF card pokes out.

I would say that some care would be needed not to damage things by impacts on the CF card. While convenient to be able to mount and unmount the card via the exposed socket access, it's not the most rugged.

This board has no jumpers but it can be configured the same way as Lo-Tech's card. It has an activity LED which is helpful but a good hack would be to add an LED to the case so you can see the LED from the front while working.

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schematic is here for reference. Note there is one barnacle on this board that needs to be done. Schematic does not reflect that.

Z171 XT-CF V2.jpg
 
Last edited:
Just a short (maybe final) note on this thread.

All of the issues with usability of this card that I am aware of have been resolved.
- the drive detection issue was resolved with a small patch to XUB
- Zenith BIOS was incorrectly reporting RAM size - again resolved with a small patch to XUB
- periodic lagginess when accessing HDD resolved by using MS-DOS 3.3 (as opposed to Zenith DOS 3.1, 3.2 or 3.3 Plus)

System works very well! I'm really happy with the performance. Checkit3 reports I/O rate of ~150 kB/sec and response time of 2.1 msec. DOS is fast and responsive and the system seems quite reliable. The CF card easily shifts between the Z-171 and a CF card reader on my desktop allowing for easy backups and software transfer.

Final system configuration
* Stock Z-171, dual 5.25 floppies, no Video card or modem installed
* 640 kB RAM
* 80C88, no 8087 (yet)
* MS-DOS 3.3
* 32MB CF card / XTIDE Universal BIOS R602 + custom patches
 
update:

A few improvements to my Z-171: First, I've added an 8087 successfully, and also I have been able to upgrade to MSDOS 5 now. The latter required additional patches to the BIOS BDA area, via custom XUB firmware.

Curret system configuration
* Stock Z-171, dual 5.25 floppies, no Video card or modem installed
* 640 kB RAM
* 80C88 + 8087-2
* MS-DOS 5
* 32MB CF card / XTIDE Universal BIOS R602 + custom patches

What's next?
* conversion from 640K of DRAM to 1MB of SRAM
* speed up from 4.77MHz to 8.0 MHz or faster if possible.


Note. I did purchase and install a V20 CPU. However, while it worked, it seemed to create video errors - random characters on the screen. So, I'm back to Oki 80C88.
 
Twospruces said:
update:

A few improvements to my Z-171: First, I've added an 8087 successfully, and also I have been able to upgrade to MSDOS 5 now. The latter required additional patches to the BIOS BDA area, via custom XUB firmware.

Curret system configuration
* Stock Z-171, dual 5.25 floppies, no Video card or modem installed
* 640 kB RAM
* 80C88 + 8087-2
* MS-DOS 5
* 32MB CF card / XTIDE Universal BIOS R602 + custom patches

What's next?
* conversion from 640K of DRAM to 1MB of SRAM
* speed up from 4.77MHz to 8.0 MHz or faster if possible.


Note. I did purchase and install a V20 CPU. However, while it worked, it seemed to create video errors - random characters on the screen. So, I'm back to Oki 80C88.
Click to expand...

I have a Morrow Pivot 2 (basically same thing) .. I have one disk that came with it that's dying but boots.. I can't get anything else to boot for me, been trying to use a floppy emulator, it seems to read the disks fine but every disk I've tried says not bootable - including the one for the Pivot off winworld, one I made off pcjs, the televideo one...letalone MS-DOS 5!?

You say no modem installed - my pivot has two ports, one rj11 and one rj45, and some modem looking circuitry; the pivot 1 has a modem speaker it looks like and similar circuitry but one port.. I'm not sure if the mainboard layout of the z171 is identical to the pivot 2 or not, I'd assume it is, the pivot 1 layout is much different.

The one with all the bodge wires is v1.
 

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Twospruces said:
So I started a project to create an XT-CF card based on the Lo-tech design a month ago.
Making some progress.
First major issue was that the "standard" ISA port on the Z170 is not well documented (in the user manual and the service manual)
* it is wired backwards relative to the standard port, so my layout was a mirror image of what was needed
* power pins are not correctly documented

Despite those setbacks I have now got a flashable card installed in my Z171.
I'm now debugging the specifics of the actual bios used, the settings, getting an FDISK.COM that works and recognizes the HDD etc etc.
Click to expand...

Can I get whatever manuals you have / pointed towards them?
 
the pivot 2 looks the same as the Z171.
The modem-y stuff is the analog that is on the main board, but the actual modem is on a daughter board which is not installed in that pic.

the schematic scans were uploaded here--
http://www.minuszerodegrees.net/manuals.htm#Zenith

good luck with it!

In the end I did get 1MB of SRAM installed and working well. I haven't gone any further with it. The XT-CF works great. Want one?
 
I have a Nec V20 in mine and haven't had video errors I've played planet X3 on it a little.

Another variation of DOS that might work well is Compaq DOS 3.31 which is what I am running (its a disk from my compaq portable II). It's supposed to support > 32MB partitions also.

I'd acutally like to build a lithum battery setup for it, ESP32 Wifi "modem", and maybe this board... the RGB board works in mine but isn't super useful.

https://www.facebook.com/video.php?v=10156390621107108
 
Twospruces said:
the pivot 2 looks the same as the Z171.
The modem-y stuff is the analog that is on the main board, but the actual modem is on a daughter board which is not installed in that pic.

the schematic scans were uploaded here--
http://www.minuszerodegrees.net/manuals.htm#Zenith

good luck with it!

In the end I did get 1MB of SRAM installed and working well. I haven't gone any further with it. The XT-CF works great. Want one?
Click to expand...
Sorry for the necro post, but is there any way I may get one?
I recently got a Morrow Pivot II, and I'm looking for ways to get files from a modern system to it.
Have you been working on any other modifications? I'm super new to this stuff, but I want to modify my Morrow II. Assuming that it works though! 😅
Oh, and speaking of which, would you happen to know the dimensions of the end of the 12v 3a power supply? The unit I bought did not come with one, and I don't know the exact size of the barrel plug.
 
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