bhaskar@fluke.UUCP (K.S. Bhaskar) (09/21/84)
If my memory serves me well, even the numbering of the 1401's memory locations were weird. But, thankfully, I haven't used the beast in a dozen years.... (The 1620 was SO much nicer!)
bprice@bmcg.UUCP (09/21/84)
>Bill Price says: >> Actually, the designers of the 1401 did something even worse than hiding it: >> they used this global thing for a very local purpose. The cell addressed by >> the address zero was used as the row counter for the card reader! To which sun!gnu replies: >This was not especially bad, considering that locations 1-80 of memory >were permanently reserved for the card reader. The "read card" instruction >(opcode "1") would fill locs 1-80 with the contents of the next card in the >reader. >101-180 was the area that would get punched if you did a "2" opcode. >201-332 got printed if you did a "4" opcode. In context, it was even less annoying, because there was no simple way to use the value of location zero: every standard instruction accessed location (n-1) [or at least generated the address of (n-1)] when reading location n. Except for the "clear storage" instruction, underflowing the address register that way would make the processor stop dead in its tracks with a red light on. With the "advanced programming" special feature, you got an instruction you could use to read that address register, so that the sequence CS 0; SBR x; would store, into x, the highest address of memory. Location 100 did not have the (n-1) problem, though. This was the card-punch row counter, in which you could usually find a '9'--the code for the last row punched. These are just a couple of the many oddities of the 1401. I'm sure that sun!gnu would agree that the 1401 was a very interesting and entertaining architecture: since it was my first machine, I'm still pretty fond of it. However, I don't know whether that fondness is because of, or in spite of, the jokes that the designers played on its users. Speaking of entertaining machines: The 1401 had mixed-radix addressing--four bits binary & three digits BCD. What machine (series) had three different radices in its mixed-radix addresses? (Answer will be given on request) -- --Bill Price uucp: {decvax!ucbvax philabs}!sdcsvax!bmcg!bprice arpa:? sdcsvax!bmcg!bprice@nosc
gnu@sun.uucp (John Gilmore) (09/24/84)
Bill Price says: > Actually, the designers of the 1401 did something even worse than hiding it: > they used this global thing for a very local purpose. The cell addressed by > the address zero was used as the row counter for the card reader! This was not especially bad, considering that locations 1-80 of memory were permanently reserved for the card reader. The "read card" instruction (opcode "1") would fill locs 1-80 with the contents of the next card in the reader. 101-180 was the area that would get punched if you did a "2" opcode. 201-332 got printed if you did a "4" opcode. Guess what happened if you executed a "7"? [It did all three at once. This was the only way to overlap I/O until much later in the 1401's design cycle.]
jc@sdcsvax.UUCP (John Cornelius) (09/29/84)
Any body remember the Hexagecimal adder? Consider the problem of subtracting two decimal numbers represented as strings of quasi-ebcdic characters, one digit at a time. Of course there was always the wordmark which was and extra bit that delineated the end of a 'thing'. As I recall the 1401 memory had bits ABC8421W where 8421 encoded the digit, AB encoded the field punches on cards, C was the parity bit and W was the word mark. Can you believe that this is the machine that brought us into the computer age? John Cornelius Western Scientific ...sdcsvax!westsci!jc
crandell@ut-sally.UUCP (Jim Crandell) (10/03/84)
>Can you believe that this is the machine that brought us into the computer age?
No. Furthermore, I can't imagine how anyone can seriously claim that it was.
That title more reasonably belongs to any number of other machines. For
example (this citing is surely controvertible, too), how about the 709 and
its offspring? They (especially the 7094) have influenced later architectures
considerably more than the 1401, unless you consider only RCA.
--
Jim Crandell, C. S. Dept., The University of Texas at Austin
{ihnp4,seismo,ctvax}!ut-sally!crandellphil@unisoft.UUCP (Phil Ronzone) (10/09/84)
>> >Can you believe that this is the machine that brought us into the computer age? >> No. Furthermore, I can't imagine how anyone can seriously claim that it was. >> That title more reasonably belongs to any number of other machines. For >> example (this citing is surely controvertible, too), how about the 709 and >> its offspring? They (especially the 7094) have influenced later architectures >> considerably more than the 1401, unless you consider only RCA. >> -- >> Jim Crandell, C. S. Dept., The University of Texas at Austin Well, in terms of numbers, I believe that there were more 1401's produced than any other 2nd generation machine. Yes, even more than the PDP-8's! I don't claim this, IBM does and DEC never claimed otherwise. The 1401 contibuted heavily to the concept of variable length byte move instruction in the 360, a now-totally-assumed concept. Yes - the 1401 probably was the machine that brought us into the computer age.