HP 9820A

THose are the common ones. Very useful the are too. The pritner alpha ROM adds the ability to print alhanumebric characters, if you do a program listing the steps are given sesnible names, not just the (2 digit octal) codes [1], and so on. It must go in the rightmost slot to work. The HP9820 has this functionality built-in. The mathcs ROM adds the trig functions, logs, etc. In the 9810, it goes in the leftmost slot and defines the keypad of half-keys in front of it. In the 9820 it can go in any slot and defines that slot's block of half keys. The manuals explain all this. [1] The 9810 memory system is a bit odd in that it stores each word in 2 consecutive locations in DRAM, odd bits in one location, even bits i nthe other. The result is that the physcial emmeoy is only half as wide as yo'd expect. So the system (stack, etc) and user data regites, which use logically 16 bit RAM actually have physcial 8 bit RAM (in 8 chuips) and the progam storage area, which is logically 6 bits wide (to store keycodes) is physciallyy 3 bits wide. This must be one of the few machines that takes 2 1103s for a memory upgrade. This is the original of my talk title 'How many bits make 9810'. YO can argue : 1 - Width of the binary ALY path 3 - Physical width of program memory 4 - Width of the BCD LAU path 6 - Logical width of program memory 8 - Physical width of system memory 16 - Logical width of system memory, CPU register size, etc RIght. It's farily common (I don't think I've seen a 9918 without it). It's worth knowing that both machines wil lwortk fine with no printer installed, I recomend brining up a minimal system to stert with amd get that going. So start out without the printer, card reader or keyboard data cable. You'll get them working. So far I've reapired several 9810s, a 9820 and a 9830 and am helping another guyy fix his 9830 by e-mail. They are complicated macbines, but not too complciated to understnad. Err, yes, well modesty would not let me say something like 'I know as much as justabotu anyone outide HP, and probably more htan anyoen inside HP now' :-) More seriously there are plenty of people who know more than me. One is on this list... You do want me to carry on talking to you, right? :-) Oh, I guess you're new here and haven't been o nteh end of my antiboardswap[ing rant. No, I am not going to repost it. All I am going to say is that tese are fine machiens nad deserve to be fixed properly. And that means amking measurement,s thinking aobut thosie measurements and then deducing what the fault is. It's not diffiuclt, and this is an ideal machien to learn on. I can talk you right through it. IS this a memory box from one of the machines? If so, which one (they are very different). If it is, the 'yellow card' is eihther the memroy data PCB (9810) or memory addres PCB (9820). It can be repaired. If it's a 9820 memory box, it's possible that it was replaed as part of the upgrade ot the neew RAM suystem (2102 RAMs), which would be interesting. You need to take a very careful look t what is inside your machines. HP part numbers for PCBs are quite helphul. THe first 5 digits are the number of the device the board was first used in, padded with leading seros. And the board handls of the 9810/20 boards give the last 2 digits of the part number using the reisstor colour code. By fr the easiest way I've found ot treacing serious logic faults in these machines makes use of the test connector on the CPU control PCB (09810-66513, so brown and orange handles, it's the same in all 9800 machines). This carries the CPU mircocode address bus. Conenct a logic analyser there and trace the microcode. Of course you need a microcode source listing to make much sense of it... -tony