What's New: New Features in Version 21.x of Prime95

# NEW FEATURES IN VERSION 21.x of PRIME95.EXE

## New Features in Version 21.4 of Prime95

1. Exiting the Torture Test now prints out how long it ran.
2. P4 error checking was relaxed slightly to reduce false alarms.

## New Features in Version 21.3 of Prime95

1. The program will now skip the P-1 factoring stage if another user has already performed this step.
2. The Advanced/Quit GIMPS menu choice now lets you quit after current work completes or quit immediately.
3. A bug was fixed in the error recovery code. After getting a "Disregard last error" message, the user was treated to a new error on every iteration. The end result was incorrect. The bug only affected the error recovery of the new P4 FFT introduced in the beta version 21.2.

## New features in Version 21.2 of Prime95

1. The program now uses the SSE2 instructions introduced on the Pentium 4 CPU. This version is about 3 times faster than the previous version on a P4.
2. The program now uses the prefetch instructions on the Celeron 2, Pentium 3, and all Athlon CPUs. This results in about a 20% performance boost on these machines.
3. Process priority is now set to idle. Microsoft documentation says that an idle thread priority overrides process priority. The program's priority scheme has always worked well. However, several Win2K users have reported that the program works better if the process priority is also set to idle.
4. The program now delays calculations until 90 seconds after bootup. This lets your machine boot up as fast as possible. This can be changed, see undoc.txt.
5. The default crossover between double-check assignments and first-time tests has been increased to a 400 MHz PII.
6. After 5 1/2 years, a help file now exists! It is HTML Help which may have problems on older Windows machines. If so, try downloading hhupd.exe from Microsoft's web site.
7. The program used to do factoring and P-1 testing on new exponents before completing LL tests on older exponents. This was confusing to many. The program now processes the worktodo.ini file in sequential order. See undoc.txt on how to restore the old behavior.
8. Error messages such as ILLEGAL SUMOUT, SUMINP != SUMOUT, etc. are no longer sent to the server since the final result contains a count of how many errors occurred during the LL test.
9. Some of the FFT crossover points have changed slightly.
10. Test/Status now outputs the day of the week each work item will complete.
11. Interim output lines have changed - hopefully, so they are more useful especially to newbies. By default, output lines no longer contain the clocks count. Lines now contain a timestamp. Benchmark timings are now output in milliseconds. These defaults can be changed using options in undoc.txt.
12. A new welcome screen for new users will encourage stress testers to use the program without reserving exponents.
13. There is now a menu choice that lets you unreserve a specific exponent. This is for knowledgeable users only. You might do this if the server assigned a small exponent and you'd rather be testing larger ones. Or the prime95 you set up on another machine had a hard drive failure.
14. The Windows 9x Service menu choice has been replaced by the more general Start at Bootup menu choice. This choice now sets registry entries to auto start prime95 on any Windows machine. WARNING: Using this option will delete any StartUp menu shortcuts so the registry entry and startup menu do not both try to start prime95.
15. Prime95 will now ask for confirmation if you enter a CPU speed that differs from the computed CPU speed by more than 4%.
16. The self-test menu choice was deleted - use the torture test instead.
17. A benchmark menu choice has been added.
18. The torture test code now includes more FFT lengths including smaller ones that run completely in the L2 cache, which may increase CPU temperatures. Each FFT size is tested for 15 minutes by default.
19. There are now several options in the undoc.txt for fine-tuning the torture test's behavior.