Author Topic: Found a weird old computer dumpster diving. (z80?)  (Read 5115 times)

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Offline tsvisimchaTopic starter

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Found a weird old computer dumpster diving. (z80?)
« on: March 27, 2020, 07:28:23 am »
I was going dumpster diving and I found a Smith & Nephew DYONICS PS3500EP Arthroscopic Surgical System. It had a cool enclosure and some nice clicky switches so I took it. Upon popping it open it appears to have a Zilog z80 CPU and a bunch of other DIP socketed chips. What I assume is the motherboard looks similar to very old PCs I've seen however this hardware is a bit before my time. Does anyone know if there's anything interesting I can do with it? I can send some pictures of the inside later if anyone's interested.

Thanks!
 

Offline daqq

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #1 on: March 27, 2020, 07:57:21 am »
Quote
Does anyone know if there's anything interesting I can do with it?
Sure, build a z80 computer.
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Offline brabus

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #2 on: March 27, 2020, 09:03:47 am »
Pics, pics, pics!
 

Offline tsvisimchaTopic starter

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #3 on: March 28, 2020, 02:28:42 am »
Here's the picture of the mainboard. I took it out of the unit to get a better picture. The rest of the components seem to be for high voltage (big transformers and scary caps) and I'm a little scared to remove them in case one of the caps is still charged (doubtful).
 

Offline tsvisimchaTopic starter

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #4 on: March 28, 2020, 02:39:02 am »
More pics
 

Offline jbeng

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #5 on: March 28, 2020, 05:03:49 am »
That's the first I've seen of 74c911 chips, had to look them up.  Turns out they're controllers for multiplexed CC LED displays, 8 segments x 4.  They're obsolete, but kinda cool, nonetheless.
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Offline greenpossum

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #6 on: March 28, 2020, 05:38:04 am »
More pics, especially under the speaker. There may be static RAM there.

There are two 16550 UARTs for the RS232 port. There is a socketed EPROM which you might like to dump to disassemble. NVRAM next to it, presumably for persistent settings. DAC and ADC chips in the middle of the board which drive the wite things. 74c911 to drive displays as already mentioned. NTSC 3.58 MHz crystal so a 4 MHz Z80. Chip dates from mid-90s.

It probably doesn't have enough RAM to run CP/M, but you might be able to make a controller not sure of what of it.
 

Offline MLXXXp

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #7 on: March 28, 2020, 01:28:21 pm »
DAC and ADC chips in the middle of the board which drive the wite things.

The white things are 4N26 optocouplers.
https://www.vishay.com/docs/83725/4n25.pdf
 

Online SiliconWizard

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #8 on: March 28, 2020, 04:37:16 pm »
Although the marking on some chips are hard to read, I can't seem to see any RAM chip on this board? Has anyone seen any?
 

Offline MLXXXp

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #9 on: March 28, 2020, 04:57:49 pm »
RAM could be just the 2K x 8 non-volatile RAM at U27, beside the EPROM, or there could be more under the speaker.
« Last Edit: March 28, 2020, 05:02:44 pm by MLXXXp »
 

Offline tsvisimchaTopic starter

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #10 on: March 28, 2020, 05:45:33 pm »
Under the speaker
 

Offline tsvisimchaTopic starter

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #11 on: March 28, 2020, 05:46:33 pm »
Another angle
 

Offline tsvisimchaTopic starter

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #12 on: March 28, 2020, 05:54:54 pm »
I have a bus pirate somewhere so I can try to dump the eeprom if someone wants to take a look at it.
 

Online rstofer

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #13 on: March 28, 2020, 06:19:24 pm »
I have a bus pirate somewhere so I can try to dump the eeprom if someone wants to take a look at it.

Disassembly from a ROM dump is a fool's exercise.  All the author needs to do is put in some bogus 0x21 (LXI  H) bytes to throw off disassembly.  The next two bytes would be an operand for the LXI H but are actually the start of some other instruction because the LXI H is never executed.  The BDOS component of CP/M has this feature.  Or at least that's what I came up with when I tried to disassemble it.  The first byte of any other multi-byte instruction will do the same thing.

Just scatter so DB 0x21 instructions in the code.

 

Online rstofer

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #14 on: March 28, 2020, 06:23:37 pm »
It might be better to remove the speaker completely.  The Z80 and the NVRAM are pretty sweet.  I don't care for desoldering but I might make an exception.  I have several Z80 systems including a complete CP/M system running on a 50 MHz eZ80.  The system just screams at that speed!
 

Offline tsvisimchaTopic starter

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #15 on: March 28, 2020, 06:35:38 pm »
Not sure if it's clear from the pictures but the nvram and the z80 are both socketed
 

Offline james_s

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #16 on: March 28, 2020, 06:36:02 pm »
There's not going to be any high voltage in that beyond the mains voltage, the capacitors are physically big but they are almost certainly just filters on a linear power supply, I'd be very surprised if any are rated over 50V and the actual voltages on them will be lower.
 

Offline MLXXXp

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #17 on: March 28, 2020, 06:41:29 pm »
U8, under the speaker, is a AY38912 sound generator. I can't quite read the number on U6 but it's probably an audio amplifier, like a TDA2002, to drive the speaker from the signal from the sound generator IC.
http://pdf.datasheetcatalog.com/datasheets2/54/545148_1.pdf
http://pdf.datasheetcatalog.com/datasheet/SGSThomsonMicroelectronics/mXyzxrtt.pdf

So, probably the only RAM is U27, which is a 2K x 8 static RAM with a lithium backup battery
http://www.greenwichinst.co.uk/datasheets/GR281.pdf
« Last Edit: March 28, 2020, 06:59:15 pm by MLXXXp »
 

Offline T3sl4co1l

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #18 on: March 28, 2020, 07:01:02 pm »
Yeah doesn't seem to have much RAM. Could be other stuff on that (likely) bus connector though. How many boards in the whole thing?

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Offline Gyro

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #19 on: March 28, 2020, 07:05:12 pm »
I wonder what was behind NS feeling the need to print "PATENTED" quite so prominently on a simple UART (16550)  back in 1994, they were commodity parts by then.  :-//
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Offline MLXXXp

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #20 on: March 28, 2020, 07:22:30 pm »
doesn't seem to have much RAM

For what the machine does, 2K is probably plenty.
 

Offline tsvisimchaTopic starter

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #21 on: March 28, 2020, 07:24:18 pm »
What kind of chips am I going to need to get if I want to build a CP/M machine?
 

Offline greenpossum

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #22 on: March 28, 2020, 08:50:10 pm »
Disassembly from a ROM dump is a fool's exercise.

However getting the code isn't the only purpose of disassembly. By looking for IN and OUT instructions one might be able to see where the peripherals are in the I/O space. Otherwise trace the address lines through the decoders to the chips.

I wouldn't bother trying to make a CP/M machine out of it. It would be easier to start from scratch.
 

Offline T3sl4co1l

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Re: Found a weird old computer dumpster diving. (z80?)
« Reply #23 on: March 28, 2020, 09:23:51 pm »
doesn't seem to have much RAM

For what the machine does, 2K is probably plenty.

I mean, obviously.  Whatever it did, it was able to do...

I have no idea what the machine does.  Did someone link the manual above and I scanned past it? ???

The ADC/DAC does suggest some analog data processing, but it could well be low bandwidth process parameters, or even housekeeping like voltages and temperatures.  My guess would be it's one or two serial interfaces, perhaps stateful with something like an ANSI command line (terminal) interface, perhaps with some relationship between the two channels (maybe one is master to a PC, the other collects data from more devices; maybe they're equivalent and it's like a multi-user terminal interface; lots of possibilities).  The 16550s (versus 8250s or Z80-SIOs) imply modest bandwidth, but obviously nothing a Z80 can't handle.  And the small RAM implies not much buffering, enough to run terminal interface(s) say, and some kind of basic state machine for the actual core functionality.

Tim
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