Title [lDOS] lDOS collects MCBs differently than MS-DOS and EDR-DOS
AuthorE. C. Masloch
Created2026-06-08 19:53:03 +0200 Jun Mon
State closed

lDOS would collect all free MCBs (both in the UMA and LMA) before every scan for allocation. MS-DOS collects free MCBs during the scan instead, so that only a single area may be collected, or only the first area (if a match is found therein).

Enhanced DR-DOS also collects free MCBs after the memory block passed to function 49h.

Reference: https://www.os2museum.com/wp/dos-memory-management/

E. C. Masloch on 2026-06-08 20:36:37 +0200 Jun Mon

First added the COMPAT=NOCOLLECTALLMCBS option in hg 2e26813f5d4a on 2026-01-02, and the COMPAT=COLLECTFREEMCB option in hg 37fdceff5b12 on 2026-01-02. Documented both in hg 37fdceff5b12 on 2026-01-02. Documentation amended in hg 20c0c9beaf41 on 2026-03-28.

See also #112, which fixed COMPAT=NOCOLLECTALLMCBS to actually be compatible with MS-DOS (v5).