plz see embedded comments below.
Dick
-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Sunday, July 04, 1999 2:01 PM
Subject: Re: OT: A call to arms (sort of)
>>
>> <This is where I'd recommend caution if you use q-bus. The schematics
must
>> <not only be available and complete, but they must be correct as well.
PAL
>> <must be fully characterized, something I've never seen in a DEC product,
>
>A lot of the time, DEC didn't copy-protect the PALs on their Unibus or
>Q-bus cards. So it is possible to get the equations out of them. That,
>combined with the schematic is enough.
>
>I have seen some DEC printests with logic equations in them. I've also
>seen one (DRV11-W?) with the PALs drawn out as gates.
>
Oddly enough, the DRV11-WA was the one board for which I saw reasonable
documentation, and it was what we used to interface to the E3-A (AWACS). I
saw no PAL equations, and, in fact, the PALs were soldered in place, so if
there were any, which I don't remember, you couldn't read them even if there
were no security bit.
>
>> Sorry, no. DEC in the handbooks provide full data, timing, and sample
>> schematics for qbus interfaces. Same for Omnibus Unibus. In that area
>
I guess I just had too little interest in DEC to notice that. Documentation
was an issue, though, and as I once mentioned, even DEC couldn't tell if two
of their machines were alike.
>
>Indeed. The PDP11 bus handbook is a very useful document.
>
>> interface (DMA capable) already there. ISA, I don't have any similar
>> concise reference for bus timing other than a few simple published
>> circuits. I've ahd to extrapolate from the XT and 8088 (and supporting
>> chips) knowledge to get things like timing and protocal for at least the
>> ISA 8bit.
>
>No, the IBM Techrefs do _NOT_ include timing diagrams, etc for the ISA
>bus. Sure you can work them out from the 8088 data sheets, etc, but the
>fact is, IBM did not fully document ISA.
>
There is a standard, however. IBM didn't create it.
>-tony
>
Received on Sun Jul 04 1999 - 16:21:09 BST