Re: RE: RE: starship-design: unmanned missions

[Steve VanDevender <stevev@efn.org>]

KellySt@aol.com writes:
 > 
 > In a message dated 2/12/98 10:25:31 PM, stevev@efn.org wrote:
 > 
 > >I also recall that the Shuttle flight computers have something
 > >like 256K of memory, which for the time was quite a bit.
 > >
 > >As far as I know the main flight computers haven't been replaced
 > >yet, although there is quite a bit of extra computer hardware on
 > >the Shuttle now, like a head-up display system.  It's not cheap
 > >or easy to replace flight control computers for man-rated
 > >hardware, especially if there's no particularly great need to.
 > 
 > They were replaced with the 256k versions.  The origionals only had  ....4K of
 > ram.  <I heard many programs curse those limits!!>

Can you document that?  The material at
http://www.hq.nasa.gov/office/pao/History/computers/Ch4-3.html
contradicts your assertion:

   Due to packaging considerations, the core memory is located
   partly in the central processor and partly in the IOP (they
   are boxed separately). However, it is still considered as a
   single unit for addressing and access. The entire memory is
   shared, not just the portion located in the individual
   boxes. Originally, 40K of core were in the CPU and 24K in the
   IOP. The memory is organized into modules with 18-bit half
   words. These contain 16 bits of data, a parity bit, and a
   storage protect bit to prevent unintentional alteration of the
   data. The original memory modules contained 8K half words, so
   6 were needed in the IOP and 10 in the CPU to store 64K full
   words. Later memory expansion consisted of replacing the CPU
   memory modules with double-density modules, in which twice the
   cores are in the same size container as a single-density
   module. So by the first flight, the Shuttle computer memories
   were 104K words or 106,496 full words of 32 bits. The memory
   access time is 400 nanoseconds, quite fast for core.