3 Dec
1998
3 Dec
'98
5:59 a.m.
The key to the elf design was minimalism and low cost.
True.
Substituting a latch and LEDs for a binary display
instead of the til311
is cheaper and more buildable.
True, but the TIL's are so cool.
using modern cmos and rams help.
At least in terms of not having to dig up 1822/2101's, yes.
The basic elf was far to minimal and frequently
expanded to get desired
functions. The basic design did not easily permit that as it didn't
decode memory or IO addresses.
Also true. One of it's big limitations. At the time, however, to
add even a 4-bit patch and more RAM would have been a major expense,
for the RAM, that is. The latch would have been under $1.
The RCA VIP or the 18S020 Evaluation board allowed far
more flexibility
with relatively little more logic. Thei cost was they had some rom.
I have a picture of that board in my RCA circular. I lusted for one
when all I had was an Elf.
This is a reproducable design. UT4 fits in 512byts of
a 2716, the rest of
the ram can be done with byte wide parts. The 1852s can be kept and the
rest were common 40xx series. With 4k of ram and UT4 (or similar)
programs like PILOT, TinyBasic, or some of the other neat software with a
terminal.
What was the memory map?
A much simplifed machine using 1802, 2 1852, 2 4028, 2
4042, 1 62256,
1 2716 and 1 6116, some glue logic for reset, run, runp and the same
serial scheme as 18S020 would give 32k of contigious ram, 2k-32byts in the
That sounds very much like what I'm designing here. Not identical,
but similar. I would need to know lots more before I could even attempt
to make it compatible.
-ethan
8000h area and the remaining 1.5k in the 2716
could hold any number of
things along with the .5k ut4 monitor. This would be a
very useful
system that could accomodate expansion for IO (more ram??????).