Dead IBM PC 5150 motherboard - help troubleshooting

[Tony Duell]

> wrote:
> > > Not a computer, but somewhere I haev a 1200 baud
> > modem that uses an 8088
> > > as a DSP (A very odd choice...)

[...]


>  Tony, if you can dig out the make and model, I'd be
> interested to hear.

Better than that, I've found the modem (although not the PSU brick for it 
yet...)

The front panel had a label stuck on it saying CASE 460/22. Under that 
was the real maker's name, Concord Data Systems. I can't, alas, find any 
Concord Data Systems model numebr on it.

Inside are 2 PCBs. The top one has the RS232 connector (DB25-S, of 
course) and 4 8-way DIP switches on it. It contains an 8031, an OTP 2732 
alongside it, lots of TTL, RS232 buffers, etc. I assume that processor 
handles the command decoding, etc. The lower PCB contains the line 
interface trasnformer and relay, lots of Op-amps and analogue bits,, an 
8088, 8155, 8259, 8253, a 24 pin EPROM (I don't want to pull the label 
off it), an ADC0804, etc. I am pretty sure that 8088 is doing some 
DSP-like task.

-tony





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