backup computer

I have been using a Sherwood Amphos Air dive computer for 5 years. No problems, no issues, air integrated, works great for me. I bought an old ScubaPro Aladdin Square with the idea of using it as a back-up. It runs on a different algorithm. What are the pros & cons of this approach? Any sage...

Yellow oceanic B.U.D. a backup computer for sale. $100 See the manual here. I've used it for fewer than 30 dives. It's in excellent condition and works great! Just clip on your BC. I'm now using a different computer as a backup.

I can get a Hollis TX-1 on eBay for about $350.00. Would this be a good deal? And would it be a good backup to my Perdix AI? Thoughts...

I Am about to Buy a console that comes with compass, presume gauge and computer. I would use the computer as my backup computer Which is better: Cressi Leonardo console, sherwood profile or aqualung i300?

I use a Perdix AI as my primary Dive Computer. I am looking for an inexpensive (but good) backup. I think it should be a wrist or hose mount where I can stow it during a dive and only access it if my Perdix fails (God forbid). I would like for the algorithms to be somewhat comparable. By...