Wednesday, 31 December 2008

Commodore 128: 8 x TOSEC Romset

"The Commodore 128 (C128, CBM 128, C=128) home/personal computer was the last 8-bit machine commercially released by Commodore Business Machines (CBM). Introduced in January of 1985 at the CES in Las Vegas, it appeared three years after its predecessor, the best selling Commodore 64. The primary hardware designer of the C128 was Bil Herd.

The C128 was a significantly expanded successor to the C64 and unlike the earlier Plus/4 it remained compatible. The new machine featured 128 KB of RAM (externally expandable to 640 KB) and an 80-column RGB monitor output (driven by the 8563 VDC chip with 16 KB dedicated video RAM, although following the release of the 128D later "flat" 128s had 64 KB of VRAM), as well as a redesigned case/keyboard with a numeric keypad. The 128's power supply was vastly improved over the 64's troublesome design.

It was much larger, with cooling vents and a fuse to protect it from blowing up. Instead of the 6510 CPU of the C64, the C128 incorporated a two-CPU design. The primary CPU, the 8502, was a slightly improved version of the 6510; its main addition was the ability to run at a 2 MHz clock rate (however, this required turning off the 40-column video output). The second CPU was a Zilog Z80 which was used for ensuring CP/M compatibility and for mode-selection of the computer upon boot-up. The two processors could not run concurrently, thus the C128 was not a multiprocessing system.

The Last V8

The C128 had three modes of operation: C128 Mode (native mode), which ran at 1 or 2 MHz with the 8502 CPU and had both 40- and 80-column text modes available; CP/M Mode, which used the Z80 second CPU in either 40- or 80-column text mode; and C64 Mode, which was very nearly 100% compatible with the earlier computer. None of these modes would have been possible as implemented on the C128 without the Z80 chip. The Z80 controls the bus on initial boot-up and checks to see if there are any C64/C128 cartridges present, and if the Commodore key (C64-mode selector) is active on boot-up. Based on what it finds, it will switch to the appropriate mode of operation.

Some 128s suffered from a reliability problem caused by the electromagnetic shield over the internal board. The shield had fingers that rested on the top of the major chips to conduct heat into the shield which then acted as a large heatsink. A combination of poor contact and the fact that plastic encased chips do not lose heat that way plus the shield being made from mu-metal (a poor heat conductor) saw some chips overheat and fail. The SID sound chip was particularly vulnerable in this respect as it operated from a 9 volt supply. The situation could be vastly improved by removing the shield completely." (Wikipedia)

Download from Megaupload:

Commodore C128 - Applications (TOSEC-v2005-07-31)
Commodore C128 - Demos (TOSEC-v2005-07-31)
Commodore C128 - Games - [D64] (TOSEC-v2006-03-06)
Commodore C128 - Games - [D81] (TOSEC-v2005-07-31)
Commodore C128 - Games - [LNX] (TOSEC-v2005-07-31)
Commodore C128 - Games - [PRG] (TOSEC-v2005-07-31)
Commodore C128 - Magazines - [D64] (TOSEC-v2005-07-31)
Commodore C128 - Magazines - [TAP] (TOSEC-v2006-03-06)

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