compucolor

[Vintage Computer Festival]

On Sat, 7 May 2005, Jim Battle wrote:

> Since we are on the subject, the purchase of the said disks motivated me
> to get my Compucolor working.  I've had it for a couple of years but
> between moving, having other old computers to tend to, and the fact that
> it was reported to have produced smoke the last time it was powered up,
> I never got around to it.

Mine produced smoke too :(  Where did yours smoke from?  I want to get
mine working again.  It seemed to have come from the CRT section.  I'll
bet I have a smoked cap somewhere.

> Disks couldn't be formatted using other computers because of the hokey
> (although dirt cheap) disk interface.  The Compucolor has a TMS 5501
> multifunction interface chip which contains, in part, a serial port
> controller.  This serial port controller is used for the RS-232 serial
> port of the machine, and it is good up to 9600 baud (but there is no
> hardware flow control).  Anyway, ISC took advantage of an undocumented
> test mode of the chip to drive the serial port at 8x speed.  The disk
> looks like a high speed serial channel and the data is simply
> conditioned and drives the r/w head of the disk drive.  I haven't looked
> into it yet, but they must be encoding each real data byte into two
> transmitted bytes in order to ensure sufficient transition density and
> no accumulated DC bias.  The net effect is that the disk holds only a
> bit over 50 KB.

Way cool!  Not as cool as the Apple Disk ][ interface though :)

I can't remember what disks I got with mine but I should dig them out and
then maybe get my CompuColor working so I can see what's on them while I
still can.

-- 

Sellam Ismail                                        Vintage Computer Festival
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International Man of Intrigue and Danger                http://www.vintage.org

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