FPGA VAX update, now DIY TTL computers

[Sridhar Ayengar]

woodelf wrote:
> Chuck Guzis wrote:
> 
>> Consider the very old Packard Bell PB250--22 bit words, fewer than 400
>> transistors and 2500 diodes, 63 instructions.  Power consumption about 40
>> watts, exclusive of I/O:
>>
>> http://ed-thelen.org/comp-hist/BRL61-p.html 
>> The trick, of course, is to use bit-serial methods.  It seems to me that
>> one could greatly simplify construction of a homebrew machine that way.
>> We're not doing this for speed, right?
>>
>>  
>>
> That is interesting reading.  Are there any of the large 48 bit 
> processors still around?
> Also TTL and memory is easy to use in 4 bit  sizes, a odd size like 18 
> bits is not so
> easy to work with.

How does parity memory work?  Must one use the extra bit for parity or 
could one use it as a ninth data bit?

Peace...  Sridhar