FPGA VAX update, now DIY TTL computers

[Scott Stevens]

On Sat, 12 Nov 2005 19:48:13 -0500
Allison <ajp166 at bellatlantic.net> wrote:

> >
> >Subject: Re: FPGA VAX update, now DIY TTL computers
> >   From: Scott Stevens <chenmel at earthlink.net>
> >   Date: Sat, 12 Nov 2005 19:27:33 -0500
> >     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
> >
> >On Sat, 12 Nov 2005 17:16:54 -0500
> >Allison <ajp166 at bellatlantic.net> wrote:
> >
> >> >
> >> >Subject: Re: FPGA VAX update, now DIY TTL computers
> >> >   From: ard at p850ug1.demon.co.uk (Tony Duell)
> >> >   Date: Sat, 12 Nov 2005 21:33:43 +0000 (GMT)
> >> >     To: cctalk at classiccmp.org
> >> >
> >> >> 
> >> >> On 11/11/2005 at 11:12 PM woodelf wrote:
> >> >> 
> >> >> >PS.  As for getting  7400 off  scrap boards, if I had the scrap boards I 
> >> >> >would most likely try to get the scrap item working again. :D
> >> >
> >> >Me too. I've got piles of obscure boards that I'd like to get going again 
> >> >sometime. Most have no real practical function, but are part of the 
> >> >history of computing/electronics.
> >> >
> >> >About the only thing I'll raid for parts are no-name clone PC 
> >> >motherboards and cards.. And those are not a good source of standard TTL, 
> >> >alas.
> >> >
> >> >> 
> >> >> There are plenty of junk boards that have no particular useful function.
> >> >> I've got a bunch of ISA cards that I salvaged.  All were old models of a
> >> >> gizmo that appeared to a PC as a monochrome adapter, but which translated
> >> >> the CPU writes to video memory to serial codes to a VT-220 type terminal.
> >> >
> >> >Now that sounds unusual enough to be very interesting. Put it this way, 
> >> >if I had something like that I'd be trying to track down a dump of that 
> >> >missing ROM. I would not be raiding it for parts. 
> >> >
> >> >-tony
> >> 
> >> There are tons of mostly unidentifyable boards with usable parts or we
> >> know what they are and maybe they even work but heck there's a stack 
> >> of 100 in the corner with good parts for salvage.
> >> 
> >> Examples of salvage to me XT clones that were never rare, 386 and 486
> >> boards with salvageable parts. A sharp TV with a dead red drive from 
> >> a doitall chip is junk for stripping.  Non-salvage items, things I
> >> keep and fix like my uVAX ADVICE as it's an in circuit emulator for
> >> the uVAX chip so it both maybe the last in existance and unusual.
> >> 
> >> There is junk and not.  The junk is there to make the not junk work.
> >> One can have too much junk, rarely!
> >>  
> >
> >XT and XT clone motherboards are becoming increasingly rare.  286 and 386 motherboards are falling into that class rapidly.  486 motherboards are still around but gradually becoming rare, too.
> >
> >What I have lying around in big annoying quantities at this point in time is all Pentium and Pentium II motherboards.  And actually, most of them are 'lying around' because they've become defective and due to the finer pitch and custom-chip construction are unservicible.  All the XT hardware I still have is either working or easily repairable.
> >
> >Full AT hardware, i.e. motherboards before the 'Baby AT' generation, is close to being 'key' as far as scarcity.  The hardware of that era was a magnitude of scale more expensive than the huge fleet 'Baby AT' that came after it.  And much of it was built like a Sherman Tank, as compared to the disposable humvee quality of the Baby AT era hardware.  Early and slow (less than 16 MHz) full AT '386 motherboards are quite rare now.  (aside- yes, in the eyes of the military the Humvee, like the Jeep before it, is a cheap throwaway transport)
> >
> >And oddly, at this point in time, people like me find ourselves with far more middle-era Sun Microsystems hardware than we can use.  Those nice little lunchbox Sparcs and Pizza Box systems are plentiful and you can cart them off in whatever quantity they are available at surplus gear auctions.  They used to be the star item at said auctions.
> >
> >There are historical books now that show all the wonderful architecture that has been destroyed, i.e. the 'Lost Twin Cities' book and video series highlights some marvelous buildings that were demolished in the name of 'progress.'  Time rolls on, and what's missed sorely 20 years after is always whatever was knocked down.  This also remains the case with old computer gear.  Nobody imagined ten years ago that anybody would have any use for a 8 MHz full-AT 80386 motherboard, so nobody kept any.
> >
> >Ummm.  Same as it ever was.
> 
> Save for the INboard386 (38616 for AT processor replacement) and the SIIG3000
> bick thats a real 5mb, IDE disk and floppy 386/16 powered system I keep as 
> it's plain handy!  It not only does VGA but RS170 video.  I do have a small 
> footprint 386/25 (or 8mhz with turbo jumper off) board I keep as its plain 
> cute and works too.
> 
> Nope nobody kept them. ;)
> 

One of the virtues of some of the 'full AT' motherboards was that they didn't use custom VLSI chips.  I mean boards like the IBM PC-AT and it's clones.  It was all done using standard TTL and the regular Intel family 8xxx LSI chips.  I am not sure if there were any 80386 motherboards made with this similar construction, but if there were, these are the boards I refer to, that have largely disappeared, and are 'classic, servicible forever' hardware, the kind the Tony likes.

Hmm, I just pulled off the shelf my copy of the 'Compaq Deskpro 386 Technical Reference Manual' and the schematic shows that it indeed used the 'classic' LSI architecture.  It has two 8259's, an 8254, two 8237's.  All standard stuff except for a few small PALs.

Is this particular tech ref manual very common?  It gives complete schematics for a '386 class machine.  I remember latching onto it back in the day specifically because of that.  

I should really try to track down a machine to go with the docs.  The first Deskpro 386 has historical merit, because it was THE first desktop '386 system (IBM at the time was foundering in their proprietary PS/2 stuff)

As we have said, most of that stuff is scrapped now.