why the Alphabetic charset is so slow

[Ulfr11]

i have noted that the alphabetic charsets are significally slower than the alpha numeric ones... why's that? is there anything that can be done ???

[philsmd]

what do you mean ? mask attack (-a 3) ?

there is no such thing as alphanumeric chars in hashcat built-in charsets: we only have the single groups of characters like ?d,?l,?u and the combination of them (together with specials, ?s): ?a
alphanumeric probably would be either using --custom-charset1 ?l?d or --custom-charset1 ?u?d or both cases --custom-charset1 ?l?u?d

You need to be more specif about what you mean.

My best guess would be that you need something like this: https://hashcat.net/faq/morework (e.g. using -S or pipe/stdin as a workaround or similar)

[TheBogeyman]

there are only 10 digits instead around 25 for letters

8 character only digit has 99999999 combinations
8 character ONLY larger LETTERS 152857890625 combinations

If that is what you mean by slow then afors.

[Ulfr11]

?h is much faster mask than ?a in brute Force attacks

[blacktraffic]

?h is much faster mask than ?a in brute Force attacks

?h is hex - [0-9a-f]
?a is "ALL" I think, not alpha, so basically all the printable ASCII - hence MUCH slower. 
?b really is all possible bytes

[DanielG]

?h is much faster mask than ?a in brute Force attacks

Yes, counting to 10 is faster than counting to 100.