The 1620 was a decimal machine. The internal data representation was
self-checking, six-bit, binary-coded decimal, with a four-bit numerical
field (1-2-4-8), a flag bit for field and sign designation, and a parity bit
(odd parity). It didn't have a fixed word length; I think the flag bit had
something to do with designating the length of an operand. Since it didn't
have registers, all operations were memory to memory.

Tom Dacon
Dacon Software Consulting


"Robert Nichols" wrote in
message ...
In article 1104981486.5847dcb424c28bd4655d5ab3bf29c2a8@teran ews,
Thomas Kendrick wrote:
:The IBM 1620 was a biquinary machine as I recall. The one that I
:worked on did not have a disk. I had the machine code manual bought
:new from IBM, but do not have it any more.

Biquinary? I believe you're thinking about the IBM 650 -- vacuum tubes,
no discs, even RAM was an optional feature (it executed directly off its
drum, instructions were not stored sequentially -- every instruction was
a branch). One number that sticks in my mind is 48,300 BTU/hr (that
comma is not a decimal point), and that didn't include the power supply,
which was another cabinet the same size as the processor cabinet. It
was the one room on campus that needed air conditioning service in the
winter.

--
Bob Nichols AT comcast.net I am "rnichols42"