PhilC wrote: 20 May 2020 20:28
No hadnt thought of that :oops:
Rom header then perhaps? Meaning you have a choice of rom types? Was just thinking about the costs of OTP roms as well btw, whereas 27c400 or 2 x 27c010 are cheap as chips?
So DIP rom's... Won't happen because..
1) We would have to do a lot of rerouting on the board and they take up a lot more space..
2) In terms of programming, it is far more annoying to program 2 chips as opposed to a single one.
3) in terms of myself producing these boards, I would also have to buy another part and stock it.. So instead of 100 ROM's, I'd have to stock 200.
4) as far as I know, DIP ROM's are not available in 55ns versions. 55ns will be needed for 32MHz operation.
5) It would also require twice as many sockets, aside from the costs, it is more soldering.
EDIT
So mouser have
AT27C020-55PU for £2.81 x 2 = £5.62
AT27C4096-55JU-T for £5.45
So DIP ROM Based on that would do nothing but take up another socket add more soldering and take more board space.
If you buy second hand stuff off evil bay and don't want to run fast-rom, I still don't think is worthwhile as you still need more sockets in more soldering.. In terms of a production environment, I would not use second-hand parts anyway.
IMHO I think going back to 2 DIP ROM's it is one huge step backwards.