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Need info to build a FPP-12A Floating Point Unit for my pdp8 straight 8

Good question, Farnell don't seem to stock them anymore. If the original design used bipolar logic then don't replace with CMOS, probably won't work. Why not emulate with a bit slice processor design? The 2900 or 29500 series. Bob
 
woodchips said:
Good question, Farnell don't seem to stock them anymore. If the original design used bipolar logic then don't replace with CMOS, probably won't work. Why not emulate with a bit slice processor design? The 2900 or 29500 series. Bob
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I want to build the missing cards for the DEC FPP-12A, I can get blank flip chip cards from the usa, I have been reading and military standard TTL would work well, so 54XX and 54XX, but is probably harder to find!
74LS is still easy to get and has about the same propagation delay as 74XX/54XX but 74LS can only drive 5X 74XX or 4X 74H, and the finding replacements for the 74H I have the same problem, the 74ALS has about the same propagation delay as the 74H but can only drive 5X 74XX or 4X 74H same as the 74LS but faster.
I may be lucky and and 74LS or 54LS will work to replace the missing 74XX and 74H?
eather way I will be using IC sockets so I can easily swap chips
 
Use LS for as much as possible, if more speed or drive is needed then try Schottky or better still the F logic. The H chips can be used for speed or drive, usually obvious which. Use 74 logic, 54 is the same but you don't need the temperature range. Just how many chips are in the FPU? Is the wiring done by PCB tracks, wire wrap, wiring pen? After 10 chips this will get pretty tedious, I always used Speedwire from Vero but no longer available unfortunately. Bob
 
woodchips said:
Use LS for as much as possible, if more speed or drive is needed then try Schottky or better still the F logic. The H chips can be used for speed or drive, usually obvious which. Use 74 logic, 54 is the same but you don't need the temperature range. Just how many chips are in the FPU? Is the wiring done by PCB tracks, wire wrap, wiring pen? After 10 chips this will get pretty tedious, I always used Speedwire from Vero but no longer available unfortunately. Bob
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The FPP-12A is built like the pdp8 straight 8, a wire wraped backplane, with loads of small flip chip boards pluged into it, the flip chips have a low dentsey of 74XX and 74H IC's, have a look at, there are high rez pics of the FPP-12A on the page
http://dustyoldcomputers.com/pdp12/fpp12.html

I dont need the temp range of the 54XX but if I can get them cheap or free I will use them, and the clock of the FPP-12A is probably very low, probably about 1 mhz, I dont know if how using TTL with different propagation delay will effect the working of the FPP-12A, I may get a race condition and glitches.
I would guess the FPP-12A would use more than 1000 TTL chips! I plan to socket them to make them easier to replace and swap.

so far I have found these chips needed
74H53, 74H00, 74H10, 74H30, 74154, 74H50, 74H53, 74H62, 74181, 74182, 7474, 74193, 74H40
but could use mil TTL
54H53, 54H00, 54H10, 54H30, 54154, 54H50, 54H53, 54H62, 54181, 54182, 5474, 54193, 54H40
 
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I have also got 2 non working 300w dec h704d power supply's to power my FPP-12A Floating Point Unit, they are good for upto 20amps @ 5v each! also I have a load of old original 74 family, and 74H chips in the post.
how meny amps or watts dose the FPP-12A use? I will find out
 
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dose anyone have a FPP-12 or FPP-12A? as I could do with some close up pics,
will two 300w power supply's be enough to run it?
 
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