Re: 6820 vs 6821 PIA

["Glenn Jones" <apple2stuff@rogers.com>]

"Michael Spangler" <mspangler@gemsi.com> wrote in message
1a410081.0411232025.220a2d80@posting.google.com">news:1a410081.0411232025.220a2d80@posting.google.com...
> I recently acquired a pair of Tektronix 4105 computers, one working
> and one dead. The dead one has been dismantled, and has 8k of odd
> sized static RAM, (neither 74LSxx width or 6502 40 pin width, but
> somewhere between) and 5 ceramic cased 6820 PIAs. And a 6800 CPU, and
> a stack of non-erasable ROMS.
>
> Anyway, do any of you hardware hackers out there know of any real
> difference between the 6820 and the 6821? I have docs on the 6821,
> didn't find much on the 6820.
>
> On a related question, some, but not all comments I can find on doing
> Apple II IO cards says to use 74LS245 tranceivers on the data bus.
> Some, but not all IO cards use the '245 as specified. How much are
> they really needed? I have at least one card without a '245, and it's
> using a 6821 directly on the bus.
>
> Thanks;
>
> Mike S.

Hi Mike,

Check this thread I started last year in may (sorry for the long link)

http://groups.google.ca/groups?hl=en&lr=&threadm=v_Eta.112009%24kYH.13047%40
news01.bloor.is.net.cable.rogers.com&rnum=2&prev=/groups%3Fq%3D74LS245%26hl%
3Den%26lr%3D%26selm%3Dv_Eta.112009%2524kYH.13047%2540news01.bloor.is.net.cab
le.rogers.com%26rnum%3D2

Glenn