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IBM Displaywriter

D

dvanaria

Experienced Member
Joined
Apr 11, 2013
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110
Location
Denver
Locally on craigslist, I just found 2 of these systems, complete with the 8" external floppy drive and the detached daisy wheel printer.

The individual systems consist of the original keyboard, cpu, and monitor.

Does anyone know the rarity or resale value of these items? I don't have any room to store them so I was going to try to sell them on ebay, but i'm just trying to justify the expense of getting them and shipping supplies and all the time that takes. Shipping would probably be in the hundreds of dollars due to the size of everything. I hate seeing items like this go to waste, they are probably destined for the landfill.

Untitled.jpg

I live in Denver Colorado so if anyone lives close by and is interested in these, they are being sold from Colorado Springs.
 
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dvanaria said:
Locally on craigslist, I just found 2 of these systems, complete with the 8" external floppy drive and the detached daisy wheel printer.

The individual systems consist of the original keyboard, cpu, and monitor.

Does anyone know the rarity or resale value of these items? I don't have any room to store them so I was going to try to sell them on ebay, but i'm just trying to justify the expense of getting them and shipping ship and all the time that takes. Shipping would probably be in the hundreds of dollars due to the size of everything. I hate seeing items like this go to waste, they are probably destined for the landfill.

View attachment 34745
Click to expand...

I used one in high school in the 90's. That showed just how far behind we were. We used it for the school newspaper. I would suppose if it were in good aesthetic shape it may be worth it if you could offload it locally. If you wanted to pack and ship it nationally/internationally is where the cost will skyrocket along with the risk of damage even with good packaging and very careful handling.
 
Damn, that's tempting! It's a six hour drive to Colorado Springs from here, but we do have friends in the area.

That said, I'm not sure that this weekend would be the best time. The Raton pass is bad enough in normal weather, let alone in snow and ice. Maybe if he still has them in the new year.
 
OK, these are now mine. A friend in the Springs was kind enough to buy them for me and SWMBO and I will drive up and collect them in the New Year. I imagine we'll make a weekend of it.:D
 
roberttx said:
OK, these are now mine.
Click to expand...

Good score! they really are a very nice system, you will be glad to have them. Displaywriters are much more advanced in terms of system architecture when compared to an IBM PC (5150) of the same era.

Getting the printer is a singular prize too, as Chuck(G) has pointed out the printers (and line protocol) are rigidly tied to the Displaywriter; they will not work with anything else and neither will the Displaywriter print to anything else.

When you get some time could you take pictures of the setup please, and if you are feeling brave please take pictures of the back of the systems and the boards inside. There is a single screw (slot-type) deep in the hole on the top of the system unit, undo the screw and you can lift off the top of the system unit and you will see the PSU and card cage. You should also look underneath the system unit and see if you have the metal-drawer installed, on some units this has the configuration paperwork (a line-printer printout) tucked inside, this can be equally fascinating about the originally shipped configuration.

We're currently lacking clear pictures of the communications cards that could be optioned with these systems; I'd be glad to find pictures of these boards so I can hunt some down and connect a Displaywriter to a remote system.

Be aware that the memory cards are old technology and can die; you will want spares on hand - they are quite dense for their era (and some have quite heroic construction techniques like stacked RAM chips).
 
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Thanks, guys. Once I get them I'll take lots of pics. The guy threw in a couple of extra base units (sans keyboards), monitors etc. for a little extra cash, so I should have spares and a better chance of finding options like comms cards.

My buddy texted me a photo, yesterday. It's all on a 4' pallet, shrink wrapped so that he can forklift it into my truck when we go there to collect it. The pile looks to be about 4' high!
 
I am collecting info on this system, to improve its emulation in MAME from current 'skeleton' level and found retroComputingTasmania's info page -- thanks for that.

Code in images from bitsavers (8493023.BIN and 8493822.BIN) doesn't look sensible, though -- f.e. here's the startup sequence:
Code: 
000FFFF0: 75 06              jne     0FFFF8h
000FFFF2: BE 0A 00           mov     si,0Ah
000FFFF5: EB 04              jmp     0FFFFBh
000FFFF7: 90                 nop     
000FFFF8: BE 04 00           mov     si,4h
000FFFFB: C6 46 1D 00        mov     byte ptr [bp+1Dh],0h
000FFFFF: 8A 00              mov     al,[bx+si]

edit: apparently, that dump is only half the ROM and its starting address is likely 0xFC000 -- disassembly has calls to absolute addresses like "call 0FC2Ch:4C4h" -- so a redump would be needed, as the 8086 starts at 0xFFFF0.
 
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shattered said:
edit: apparently, that dump is only half the ROM and its starting address is likely 0xFC000 -- disassembly has calls to absolute addresses like "call 0FC2Ch:4C4h" -- so a redump would be needed, as the 8086 starts at 0xFFFF0.
Click to expand...

I've made an attempt to extract the Displaywriter ROM using DDT86[1]. I probed around the memory addresses and on my machine (that has 256KB of memory) I have the following memory map:

0000:0 - 3FFF:F RAM (256KB)
4000:0 - EEFF:F nothing (reads as FF)
EF00:0 - EFFF:F RAM (4KB) - display-memory?
F000:0 - FFFF:F ROM (64KB)

At FFFF:0 there is a jmp far ptr 0FC05:4

Email me (nw@retroComputingTasmania.com) if anyone wants a copy of the 64KB binary file.


[1] run CCP/M-86 on DW, use DDT86 to Write memory to 8-inch diskette, IMD from PC with 8-inch diskettes, IMDU --> BIN file, CPMtools (cpmcp using appropriate diskdef) files from image.
If I do a dd if=ROM of=ROM.txt conv=ascii I can see this EBCDIC string embedded in the ROM "0123456789ABCDEFCPD9999 IBM6580"
 
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Various pictures I've taken of my Displaywriter running the demo version of Concurrent CP/M-86; note the ones at the bottom of the album are where I was using DDT86 to get an image of the ROM. Note the one that shows the 256KB memory boundary and where CCP/M-86 has planted some strings.

https://goo.gl/photos/UCH2TnfBunPub6xNA

I tried to attach an image to this post but it was upside down since somewhere in the labyrinthian mess that is iOS, web-stuff etc something doesn't understand the orientation metatag on photos...
 
shattered said:
I am collecting info on this system, to improve its emulation in MAME from current 'skeleton' level ...
Click to expand...

Very glad to hear about getting full-support into MAME, this would be wonderful to see.

I've been thinking about strategies, and two ideas spring to mind. We could hunt down the XBIOS section of CCP/M-86 and use that to decode the entry points into the Displaywriter ROM. As I've suggested elsewhere I expect the CCP/M-86 usage of the Displaywriter ROM is minimal, they only did enough to get something on the screen and for it to boot. The second option is to extract the BIOS shim from the UCSD p-System, again fairly easy to find and dig out the ROM entry points. This would at least provide some ROM entry points. Additionally the Displaywriter uses many standard Intel support chips and they should reveal themselves in the ROM too. I expect the main complexity in the Displaywriter ROM is a very large section of code for the self-test and built-in diagnostics as these were quite extensive.
 
nigwil said:
0000:0 - 3FFF:F RAM (256KB)
F000:0 - FFFF:F ROM (64KB)
Click to expand...
A bit of poking about in the memory snapshot suggests the ROM is in fact 16KB in length, either I did something wrong or it is repeated 4 times in the upper memory range.
The ROM memory range is therefore:

FC00:0 - FFFF:F (16KB)
 
nigwil said:
Very glad to hear about getting full-support into MAME, this would be wonderful to see.

I've been thinking about strategies, and two ideas spring to mind. We could hunt down the XBIOS section of CCP/M-86 and use that to decode the entry points into the Displaywriter ROM. As I've suggested elsewhere I expect the CCP/M-86 usage of the Displaywriter ROM is minimal, they only did enough to get something on the screen and for it to boot. The second option is to extract the BIOS shim from the UCSD p-System, again fairly easy to find and dig out the ROM entry points. This would at least provide some ROM entry points. Additionally the Displaywriter uses many standard Intel support chips and they should reveal themselves in the ROM too. I expect the main complexity in the Displaywriter ROM is a very large section of code for the self-test and built-in diagnostics as these were quite extensive.
Click to expand...

Maybe there's a simpler way -- does maintenance manual explain how the devices are mapped in memory?

+ there's some info in CP/M-86 reference manual for DW (http://www.nostalgia8.nl/cpm/ibm/cpm6dwrm.pdf) -- f.e. that Control-End causes a power-on-reset, brief description of video memory layout in Section 6...
 
Just in case it's relevant to anyone...

Some years ago, I rescued the floppy disk unit for one of these, 2 @ 8" drives, one SSSD, the other DSDD. I also kept some manuals, I think for the whole system. I'd always wanted to do something with 8" drives, maybe attach to something else like a CP/M system, but looking inside, I'm not sure. Anyway, the unit is in pretty clean condition.

Looks like a mains motor for the main drives for the disks?

Oh, in case anything happened, I've got a box of 10 mint 8" floppies!

Geoff
 
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