MODCOMP II Revisited... It's running again!!!

Lyle Bickley lbickley at
Sat Jul 14 18:25:19 CDT 2007

On Saturday 14 July 2007 14:51, William Maddox wrote:
> --- Lyle Bickley <lbickley at> wrote:
> > 2) Obtain all the chips you'll need up front from
> > your "stash" and buying as
> > required. Bag or box them in numeric order near the
> > system. In my case, I
> > needed to acquire a lot of chips - as I had very few
> > 74H and 74S series in
> > stock - and the "fast" MODCOMP II needed scads of
> > them.
> Hi, Lyle.  Do you have a good source of mixed-lot or
> small quantity 74H series parts?  I've picked up a few
> odd lots, but to get any selection, it looks like you
> have to go to the legacy chip merchants who have large
> line-item minimum orders.

I used a fair number of "pulls" from another/different MODCOMP which had been 
previously "updated" with new chips.

I also obtained chips from friends and sources that for privacy reasons I will 
not mention. In some cases, I literally ran folks out of some series of "H" 
chips. I also bought some chips in quantity (lots of 25 or more per type). By 
the time I complete restoring I/O, I'll probably only have a few left as 

Of course, I could have resorted to substituting "S" for "H" - they are a lot 
easier to come by - but I wanted to restore the MODCOMP II as one would an 

> Congratulations on getting the Modcomp restored.
> As for the guy who asked about "but will it run
> Linux?", I doubt it, but I get you could get v6 or
> v7 to run on it. ;)  

I don't think MODCOMP II was ever capable of running any *NIX. It only 
supports 64KW (128KB) of memory - and has no memory mapping. However, I do 
plan to run MODCOMPs MAX OS on the II.

> You have an I/O box.  Does it 
> have a disk controller for the Diablo 30?

I don't have a Diablo - only a paper tape reader, floppy disk interface, 
console (RS-232) and High Speed Serial interface - and a "customer" created 
interface that looks like some kind of analog data sampling device.

My next project is getting all the peripherals to work (with the exception of 
the "customer" interface (I'm still searching the source archives for any 
information on it).

Lyle Bickley
Bickley Consulting West Inc.
Mountain View, CA

"Black holes are where God is dividing by zero"

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