Newly aquired Tandy 6000HD! Lots of questions to follow...

[pski]

Don't turn it off! :D

This is actually the recommended practice. The Tandy version of the System Administrator's Guide to Xenix states:

"We recommend, however, that you leave your system up and running 24 hours a day. Password protection makes your files secure, and the continuing successful operation of your hardware is more assured if the system is not turned on and off with any frequency. The cost of power to keep it running is offset by fewer hardware repair bills and less down time."

Of course, as you alluded to, this could also be interpreted as

"If your state-of-the-art Model 6000 68000 Xenix system is working...don't touch it!"

 

[Chromedome45]

LOL but it makes a whole lot of noise! Noisiest computer I have ever owned. Plus it throws off a lot of heat.

 

[pski]

I don't have an answer to your question yet, as I haven't studied the circuitry of either of our memory boards yet. 9 bits per byte generally implies parity detection support in my experience, but I don't know yet whether parity checking is implemented in the 16 series 68000 subsystem. I just haven't looked into the internals that carefully yet.

Parity was optional and if enabled it was installed in U38, U39, U58 & U59. Mark's board looks like it has 512K (2 banks of 256K) and the holes but not the sockets for the parity chips. Chromedome45 has just 1 bank of 128K or 256K and the sockets soldered in but not the chips for parity. So, neither board has parity enabled.

The 68000 16bit memory was actually implemented as 2 parallel 8bit segments probably since I/O was handled using the 8bit Z80. So, 2 banks of 2 segment 8bit memory requires 4 parity bits, hence the 4 empty chip sockets on both boards.

 

[Chromedome45]

I thought mine has 512k of RAM! That was standard on the 6000.

 

[pski]

You're probably right. I can't read the chips in your picture.

 

[Chromedome45]

Verified has 512K 2 rows of 8 256K chips. The extra sockets can be ignored as well as the 4 empty ones below them. They are not used.

 

[Chromedome45]

So keyboard arrived and little crossover cable does work. However most of the foam pads were bad. Found an older keyboard and swapped
over newer pads. But one problem space bar does not work. I do not know why. Any ideas out there. Also when booting up to xenix I press enter and I get an error no68K does that mean the 68000 board is bad? I hope not.

 

[pski]

Also when booting up to xenix I press enter and I get an error no68K does that mean the 68000 board is bad? I hope not.

Did you try reseating the 68k boards?

 

[Chromedome45]

Yes I did. I honestly think the install is corrupt. I have the Xenix disk images just need to create them. Hence the 8" to 5.25" floppy thread.

 

[Chromedome45]

Ok for the 6000/16b experts what good is adding the additional 16K to the main logic board? I thought you could 64K chips as well or am I off course?

 

[NF6X]

I think I read about them recently in the Model 6000 service manual. If I'm not mistaken, those sockets on the main board are just for adding the 16k bank when it is not already present on another board such as the 68000 board or hard disk drive controller. So they might be used in a cageless Model 12 to allow TRSDOS II to be run, but serve no purpose in a 6000 where the memory is provided by one of the installed cards. I'm not 100% positive about that, though.

 

[pski]

I think I read about them recently in the Model 6000 service manual. If I'm not mistaken, those sockets on the main board are just for adding the 16k bank when it is not already present on another board such as the 68000 board or hard disk drive controller. So they might be used in a cageless Model 12 to allow TRSDOS II to be run, but serve no purpose in a 6000 where the memory is provided by one of the installed cards. I'm not 100% positive about that, though.

This is generally my understanding. The 6000 has an option of installing 64K in the upper bank instead of 16K for a total of 128K Z80 memory. Not sure what would use this additional 48K. Maybe Xenix could take advantage of it for I/O.

Edit: I found it. Technical Bulletin 12/16B:18. The 64K upgrade is part of the Banked CP/M upgrade procedure. This was used by CP/M Plus which was a Tandy badged version of CP/M 3 from DRI. This version of CP/M had a memory banking option apparently and could utilize 128K.

 

[Chromedome45]

Could possibly use as a ram disk under LS-DOS as well I would think. The memdisk/dct is on that disk.

 

[lowen]

How to use the extra 64K with LS-DOS is included in the README/DOC that comes with LS-DOS; I posted a copy in the 'Definitive OS List for Model II' thread.

 

[Chromedome45]

Ok so I am trying to install 64k RAM into the upper memory bank on the main logic board I set all jumpers to there appropriate position and in doing so I knock out the HD Controller! Found out it has something to do with jumper E50,E51,E52 when set to 64k E50-52 is when the HD quits. Put to E51-52 and HD works again. A little confused. Memory banking address at E32-E39? I have it set at E32-E39

 

[pski]

Take a look at the Tech Bulletin 12/16B:18. Apparently there is more to do than just putting in the RAM chips and switching jumpers.

 

[Chromedome45]

Ok downloading it. Big file!

 

[Chromedome45]

Ok looked at that tech brief I still have the 4 caps in place and most likely the older PROM. Ok so Pulled RAM and set jumpers back to where they should be. Oh well!

But I did bring my memory board up to 1 Meg though.

 

[lowen]

Take a look at the Tech Bulletin 12/16B:18. Apparently there is more to do than just putting in the RAM chips and switching jumpers.

As I recall, there's a replacement large chip required; an 82S100 or similar, for the address decode change. This is the unobtainium piece; I did a Model 12 with the 64K back in the day, and I think I got one of those chips from either Bill Dixon or David Dalager; but that's been twenty years ago when I still owned a Model 12 (and a 16B, and a 6000......). Shame that there wasn't this much interest back then, as back then you couldn't give the machines away, and mine all ended up as parts and scrap. Although I think I shipped some stuff to Kelly along with the service manual, but I don't recall exactly. I kept very few 8 inch disks mostly as keepsakes; but later on I sent copies of LS-DOS to Tim Mann (I think I actually still had a Model 12 at that point, as it is what made those copies in 2000).

 

[pski]

As I recall, there's a replacement large chip required; an 82S100 or similar, for the address decode change. This is the unobtainium piece; I did a Model 12 with the 64K back in the day, and I think I got one of those chips from either Bill Dixon or David Dalager; but that's been twenty years ago when I still owned a Model 12 (and a 16B, and a 6000......). Shame that there wasn't this much interest back then, as back then you couldn't give the machines away, and mine all ended up as parts and scrap. Although I think I shipped some stuff to Kelly along with the service manual, but I don't recall exactly. I kept very few 8 inch disks mostly as keepsakes; but later on I sent copies of LS-DOS to Tim Mann (I think I actually still had a Model 12 at that point, as it is what made those copies in 2000).

I believe it. I am a very recent fan of theses machines and I go crazy when I look back at postings from the 1990s and early 2000s where folks are literally giving away these machines.