What MAC did SSLv3.0 use? How did it compare to HMAC in TLS 1.0 and above?
The key was concatenated in SSL 3.0:
    hash(MAC_write_secret + pad_2 +
         hash(MAC_write_secret + pad_1 + seq_num +
              SSLCompressed.type + SSLCompressed.length +
              SSLCompressed.fragment));

but XOR'ed in HMAC:
    H(K XOR opad, H(K XOR ipad, text))