to enable or disable the character ROM for any VIC-II bank via the register at . Also, there are two sets of color RAM—one visible to the CPU, the other to the VIC-II and the user may select what chip sees what. In CP/M mode, the Program Segment Prefix and Transient Program Area reside in Bank 1 and the I/O registers and CP/M system code in Bank 0. The C128's RAM is expandable from the standard 128 KB to 256, 512 or even 1,024 KB, either by using commercial memory expansion modules, or by making one based on schematics available on the internet. Commodore's RAM Expansion Units use an external 8726 DMA controller to transfer data between the C128's RAM and the RAM in the expansion unit. C128D Late in 1985, Commodore released a new version of the C128 with a redesigned chassis resembling the Amiga 1000. Called the Commodore 128D, this new European model featured a plastic chassis with a carrying handle on the side, incorporated a 1571 disk drive into the main chassis, replaced the built-in keyboard with a detachable one, and added a cooling fan. The keyboard also featured two folding legs for changing the typing angle. The C128 released in the United Kingdom on 25 July 1985, and in North America in November 1985. According to Bil Herd, head of the Hardware Team (a.k.a. the "C128 Animals"), the C128D was ready for production at the same time as the regular version. Working to release two models at the same time had increased the risk for on-time delivery and was apparent in that the main PCB has large holes in critical sections to support the C128D case and the normal case concurrently. In the latter part of 1986, Commodore released a version of the C128D in North America and parts of Europe referred to as the C128DCR, CR meaning "cost-reduced". The DCR model features a stamped-steel chassis in place of the plastic version of the C128D (with no carrying handle), a modular switched-mode power supply similar to that of the C128D, retaining that model's detachable keyboard and internal 1571 floppy drive. A number of components on the mainboard were consolidated to reduce production costs and, as an additional cost-reduction measure, the cooling fan that was fitted to the D model's power supply was removed. However, the mounting provisions on the power supply subchassis were retained, as well