Zenith Z-171 BIOS variants

[Twospruces]

hello Z-171 owners-
I understand that the Z-171 BIOS went through a lot of iteration during production.
I am interested in gathering up various BIOS images.

There are 3:
1) Main system BIOS
2) Video BIOS
3) Keyboard BIOS

If you can gather these binaries from your machine (using software or an EPROM reader) and post them here, that would be great!

thanks-

 

[Retroplayer]

Bios date of 3/14/1985. All ROMS in the zip.

 

[Twospruces]

Interesting. My bios has the same date but is totally different. Thanks for this.

 

[Retroplayer]

Did you already post your BIOS somewhere?

 

[bladamson]

I haven't cracked open my 171 yet, but I'll try to remember to dump the roms and post them for you when I do.

 

[Twospruces]

After looking at mine again, I realized that I mis-read my eproms, all except the main system bios, which is here.

I'll try again for the video and keyboard roms.

 

[Retroplayer]

Wow. Yeah, yours is very different. I notice mine has 2033 in the header and yours has 2029. That might be a version number.

 

[Twospruces]

Here is my ROM set.

* the 32k system BIOS is, as you say, very different. I guess this 32k image contains video BIOS as well as system BIOS.
* the 8k keyboard BIOS is quite different as well. I see no embedded date.
* the 8k Display Offset is identical.
* the 32k character ROM is really close, minor differences.

I'm tempted to try your ROM in my machine and see if it is better behaved. I had an issue trying to use V20. Would be nice if that was fixed.

 

[Retroplayer]

I'm sure it wouldn't hurt anything if you tried it.

Did you receive my private message from the other day? I didn't see a response.

 

[Twospruces]

So there is a system bios marked 444-415.
There is also one marked 444-417.
Thugwaffle's parts machine.

 

[Retroplayer]

The chip labeled 444-415-1 on my system is the KB ROM. My bios did not have a label on it, which is odd. I don't have a -417 listed, so maybe that is my BIOS?

 

[Twospruces]

Ah. On thugwaffles Machine the kb bios sticker fell off.

 

[Scruit]

I just dumped the roms from mine. BIOS sticker date "27SEP85" but the internal date in the header is 3/14/1985 with code 2029

00000000: 3033 2f31 342f 3835 db8c 00f0 5a44 5320  03/14/85....ZDS
00000010: 434f 5250 3230 3239 82aa 42aa 8255 4255  CORP2029..B..UBU

 

[Twospruces]

Interesting thanks!
Will check this out

 

[Twospruces]

I just dumped the roms from mine. BIOS sticker date "27SEP85" but the internal date in the header is 3/14/1985 with code 2029

00000000: 3033 2f31 342f 3835 db8c 00f0 5a44 5320  03/14/85....ZDS
00000010: 434f 5250 3230 3239 82aa 42aa 8255 4255  CORP2029..B..UBU

All of your ROM images are the same as my original ones, except for the Character ROM.
Your character ROM is
2K__PIVOT_2ZE_2K-04point8_NORMAL__TC57256
Mine had no label.

Your character rom is very different, I wonder why.

thanks for sharing!

 

[Scruit]

Well... I could not get my 171 to fully start - it gave me a message saying it was testing memory, then it stops with just a flashing cursor.

The 171 is new to my collection and so far it has only gone through my normal 'intake' process (check for shorts / psu voltages, capture jumper/dip settings, dump roms, then attempt power up). Seller has said it failed memory test and I verified it still has the same symptoms. I ran all the socketed memory chips through my RCT and found two bad ones. Those are on order, then I'll start it back up again and try to get further.

I'm hoping that being able to see and read the memory testing message means my character rom is working fine. I'm not sure what the layout of the character rom is - if I can identify the chip that creates the video signal (like the Yamaha V6366 is used in the SupersPort) then maybe the datasheet will explain how it reads the characters from the ROM.

Considering the other roms are identical, it may be that my character rom is messed up, or maybe it's a different font? If it has problems then I could test with a copy of the character ROM that you posted in this thread.

 

[Twospruces]

The differences in the character rom are interesting.
Some of the data is extremely different.
Other, the majority, parts of the ROM are structured with similar data, but "backwards". If you look at 16 byte sets, the sets seem to relate but the 16th 15th 14th.. byte in one set is like the 1st 2nd 3rd... byte in the other set.

 

[Twospruces]

Well... I could not get my 171 to fully start - it gave me a message saying it was testing memory, then it stops with just a flashing cursor.

IIRC mine gave an error message that identified where in memory the error occurred.

The 171 is new to my collection and so far it has only gone through my normal 'intake' process (check for shorts / psu voltages, capture jumper/dip settings, dump roms, then attempt power up). Seller has said it failed memory test and I verified it still has the same symptoms. I ran all the socketed memory chips through my RCT and found two bad ones. Those are on order, then I'll start it back up again and try to get further.

You could reduce the RAM quantity and reconfigure the jumpers. I think that info is in the manuals online.

I'm hoping that being able to see and read the memory testing message means my character rom is working fine. I'm not sure what the layout of the character rom is - if I can identify the chip that creates the video signal (like the Yamaha V6366 is used in the SupersPort) then maybe the datasheet will explain how it reads the characters from the ROM.

This machine has a video subsystem that is built from discrete parts. The video RAM chips are constantly polled for data; that data is pushed into the LCD drivers by a counter based subsystem. Cursor location is stored in a separate RAM chip. The keyboard processor is responsible for generating an NMI interrupt that pushes a new character into the video RAM.

Considering the other roms are identical, it may be that my character rom is messed up, or maybe it's a different font? If it has problems then I could test with a copy of the character ROM that you posted in this thread.

Seems reasonable. Should confirm PCB revision as well, just in case..

 

[Plasma]

The differences in the character rom are interesting.
Some of the data is extremely different.
Other, the majority, parts of the ROM are structured with similar data, but "backwards". If you look at 16 byte sets, the sets seem to relate but the 16th 15th 14th.. byte in one set is like the 1st 2nd 3rd... byte in the other set.

It's possible the character data is the same but the address and/or data lines on the board are wired non-standard. Thus when you read the EPROM using a standard pinout, it appears different.