FPGA VAX update

[Allison]

>
>Subject: Re: FPGA VAX update
>   From: Scott Stevens <chenmel at earthlink.net>
>   Date: Wed, 02 Nov 2005 18:16:11 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>> However the most interesting is the Block 1 AGC (apollo guidence computer).
>> 
>
>Depending on how much 'from scratch' people feel is necessary, it's also interesting to roll your own computer using an off-the-shelf processor (or multiples).  I have a simple 8088-based SBC design wired up and waiting for motivation to put together some test firmware.  The main thing that has kept me from bringing it up is the difficulty in getting x86-based machine language development tools going.  I'm used to little 4 and 8-bit assemblers where you can plop down a few ORG statements and have it all resident in a ROM, and almost all the x86 asm tools start from the assumption you are running on DOS and have no direct control of the memory map.
>
>Z80 designs are also fun and easy.  And I still have those tubes of 6100 processors. . .

I have z80s, 8085s, 6100s and 6120s, 1802s, T11s(PDP-11), 9900s, 6800s, 6809s,
804x, 805x to name a few to play with.  I tend to zero in on Z80, 1802, 6100
and 8039(8048) as being interesting.  Each of those has some aspect of computing
that it handles elegantly and other parts that are plain dirty.


>Certainly using a micro is by no means as cool as making your own machine 
>from small and medium-scale logic, though.  I think it would be neat to 
>build one using discrete transistors.  Not as difficult as a valve-based
>design, but just as deep into the circuitry.

It is.  Often it's really just trying to understand the genie with 40 pins.
For me it was started by my contact with the PDP-8I.  It just seemed so 
buildable.  While I've not built one of TTL other have.  So I've done 4bitters
and 8 bitter in TTL and one day I'd like to try something bigger. 

Valves are harder due to power, heat and most importantly size. A few hundred
miniature duo-triodes will fill several racks.



Allison