They are certainly not universally interchangeable. The 604ev in the "Kansas" 8600 (250-300MHz model) and in the 9600 (300-350MHz model) is not compatible with earlier logic boards that shipped with either the 604 or the 604e in the series (including, for instance, the 8600/200 and the 9600/200). As far as I know, the 604/ 604e cards from the earlier machines are also not compatible with these "Kansas" logic boards. I'd be astonished if they were.
Broadly speaking, however, any 604/ 604e card can be swapped around between machines earlier than the Kansas models — despite the fact that some 604e cards have "for 9500 only" written on them, it ain't necessarily so.... But I would be reluctant to say that the swapping can be universally done.
The first place where things can get marginal is in bus speed, which is set by the card. The earlier the machine, one suspects, the more likely it will be that the thing will be happiest running at less than 50MHz (the 200MHz 604e card sets the bus at that speed, so a slower card may be better).
The second place is the L2 cache, which can fool things up royally. In particular, DUAL 604e cards, such as the dual 180MHz and 200MHz cards that shipped in the 9500MP and 9600MP, are notorious for being very sensitive to L2 cache speed, and this can be a nuisance. On an 8500 (or a 7500, 7300, and 7600 for that matter), this is not such a big deal, as the L2 cache may not be present or can be easily removed, but it can be a bigger deal in the case of an early 9500 logic board, because there 512k L2 cache is soldered on.
G3 cards are a separate issue, but I take it that you were asking about the original G2 processor cards.
Broadly speaking, however, any 604/ 604e card can be swapped around between machines earlier than the Kansas models — despite the fact that some 604e cards have "for 9500 only" written on them, it ain't necessarily so.... But I would be reluctant to say that the swapping can be universally done.
The first place where things can get marginal is in bus speed, which is set by the card. The earlier the machine, one suspects, the more likely it will be that the thing will be happiest running at less than 50MHz (the 200MHz 604e card sets the bus at that speed, so a slower card may be better).
The second place is the L2 cache, which can fool things up royally. In particular, DUAL 604e cards, such as the dual 180MHz and 200MHz cards that shipped in the 9500MP and 9600MP, are notorious for being very sensitive to L2 cache speed, and this can be a nuisance. On an 8500 (or a 7500, 7300, and 7600 for that matter), this is not such a big deal, as the L2 cache may not be present or can be easily removed, but it can be a bigger deal in the case of an early 9500 logic board, because there 512k L2 cache is soldered on.
G3 cards are a separate issue, but I take it that you were asking about the original G2 processor cards.