On Windows, it works for memory bitmaps. I just tested it.
I've also been running some informal tests with my ThreadPool. 8 jobs versus 1 is faster by a factor of between 2 and 3 times.
This is some example code that uses my ThreadPool class that I've put together over the last few days. I will integrate it into Eagle soon, but this version is standalone (only depends on Allegro 5). API is super simple.
1#include "Pool.hpp"
2
3class Data {
4public :
5 int x;
6 Data() : x(0) {static int i = 1;x = i++;}
7};
8void* Factorialize(ALLEGRO_THREAD* t , void* data) {
9 Data* d = (Data*)data;
10 int z = d->x;
11 while (--z) {
12 d->x *= z;
13 }
14 return data;
15}
16int main(int argc , char** argv) {
17 if (!al_init()) {return -1;}
18
19 const int NDAT = 100;
20 Data* dat = new Data[NDAT];
21
22 ThreadPool tpool;
23 tpool.SetNumThreads(8);
24 for (int i = 0 ; i < NDAT ; ++i) {
25 tpool.AddJob(Factorialize , &dat[i]);
26 }
27
28 tpool.Start();
29 tpool.Finish();
30
31 for (int i = 0 ; i < NDAT ; ++i) {
32 Data* d = &dat[i];
33 printf("%d factorial is %d.\n" , i + 1 , d->x);
34 }
35
36 return 0;
37}
I'm not going to post it yet, for some reason I can't have more than exactly 853 jobs. 
If I add 854 jobs or more, the thread pool breaks and never finishes its work.
UPDATE :
I fixed avoided the strange thread problem and have a working implementation of a thread pool now. You can see it here :
https://www.allegro.cc/forums/thread/617504