=== Amstrad's implementation of CPM 2.2 ===
CP/M 2.2 was distributed with the DDI-1 disc interface, the CPC464CPC664, and on side 1 of the CPC6128 system discs. It provided 43K 41K TPA. CP/M 2.2 uses the firmware, and the platform specific part of CPM BIOS is in the AMSDOS ROM, and this calls into it through to the firmware through a special "ENTER FIRMWARE" function in . By having the disc BIOS in ROM. 43K is the max useable ram when , using the firmware is active and having the screen is at &c000-&ffff, this gives 41K as the TPA for a CPC 64KB system.
* Amstrad CPM2.2 uses Amstrad's "System" format. This is 40 tracks, 1 side, 9 sectors per track numbered &41-&49. Each sector holds 512Bytes. There are two reserved tracks, then the directory which has 64 entries, and then the data area.