Altair parts substitutions

From: Dwight Elvey <elvey_at_hal.com>
Date: Tue May 23 19:06:34 2000

ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
>
> Now that's interesting. When I got my (second-hand) Intellec MCS8i, it
> didn't work. One of the faults was soon traced to an 8205 chip on (IIRC)
> one of the memory boards.
>
> At the time I'd never heard of this device (and didn't have a suitable
> Intel databook), but from the schematics in the manual it appeared to
> have the same pinout as an 74LS138. So I stuck one of those in and of
> course it worked fine (and still works AFAIK).
>
> I wondered at the time what the difference was between an 8205 and a
> 74LS138. Now I know...
>
> -tony

Hi Tony
 As I recall, the difference was that the Intel parts could
stand a much lower negative voltage ( -10V? ) than the general purpose
TTL. This made is compatible with the 8080's. Also, as
I recall, the 8205 were also Schottky's.
Dwight
Received on Tue May 23 2000 - 19:06:34 BST