This Handheld C64 Design Study Needs To Be Made
The Commodore 64 remains the best selling home computer of all time, and is unlikely to be toppled anytime soon. It continues to inspire a diehard community of makers and hackers to this day. [Cem Tezcan] is one of those people, and his design study of a handheld C64 is utterly droolworthy.
This Handheld C64 Design Study Needs To Be Made
[Jason] sent in this nice palmtop C64 (cache) project based on a PSone screen. Notable hacks: PIC 16F88 to encode rs-232 to PS/2 keyboard output, Atari keychain joystick and a SD card slot (not functioning yet). The case was made of wood and laminated over with contact paper.
The portable C-64 is an example, aiming at a slightly different buyer. Not much change there, but as LCD displays improved, a few more years might have done this. The Radio Shack Model 100 came out in 1983, a mix of moving forward, and backward from the C-64. But proof that a portable was almost viable concurrent with the C-64. And static RAM did become denser around that time, though it would require a redesign. Someone pointed out the 65C02 was available, so the real issue was maybe some perioheral ICs, the screen, and maming it small.
The product was code named the VIC-40 as the successor to the popular VIC-20. The team that constructed it consisted of Yash Terakura, Shiraz Shivji, Bob Russell, Bob Yannes, and David A. Ziembicki. The design, prototypes, and some sample software were finished in time for the show, after the team had worked tirelessly over both Thanksgiving and Christmas weekends. The machine used the same case, same-sized motherboard, and same Commodore BASIC 2.0 in ROM as the VIC-20. BASIC also served as the user interface shell and was available immediately on startup at the READY prompt. When the product was to be presented, the VIC-40 product was renamed C64. The C64 made an impressive debut at the January 1982 Consumer Electronics Show, as recalled by Production Engineer David A. Ziembicki: "All we saw at our booth were Atari people with their mouths dropping open, saying, 'How can you do that for $595?'" The answer was vertical integration; due to Commodore's ownership of MOS Technology's semiconductor fabrication facilities, each C64 had an estimated production cost of US$135.
The C64's designers intended the computer to have a new, wedge-shaped case within a year of release, but the change did not occur. In 1986, Commodore released the 64C computer, which is functionally identical to the original. The exterior design was remodeled in the sleeker style of the Commodore 128. The 64C uses new versions of the SID, VIC-II, and I/O chips being deployed. Models with the C64E board had the graphic symbols printed on the top of the keys, instead of the normal location on the front. The sound chip (SID) was changed to use the MOS 8580 chip, with the core voltage reduced from 12V to 9V. The most significant changes include different behavior in the filters and in the volume control, which result in some music/sound effects sounding differently than intended, and in digitally-sampled audio being almost inaudible, respectively (though both of these can mostly be corrected-for in software). The 64 KB RAM memory went from eight chips to two chips. BASIC and the KERNAL went from two separate chips into one 16 KB ROM chip. The PLA chip and some TTL chips were integrated into a DIL 64-pin chip. The "252535-01" PLA integrated the color RAM as well into the same chip. The smaller physical space made it impossible to put in some internal expansions like a floppy-speeder. In the United States, the 64C was often bundled with the third-party GEOS graphical user interface (GUI)-based operating system, as well as the software needed to access Quantum Link. The 1541 drive received a matching face-lift, resulting in the 1541C. Later, a smaller, sleeker 1541-II model was introduced, along with the 800 KB 3.5-inch microfloppy 1581.
The C64 uses an 8-bit MOS Technology 6510 microprocessor. It is almost identical to the 6502 but with three-state buses, a different pinout, slightly different clock signals and other minor changes for this specific application. It also has six I/O lines on otherwise unused legs on the 40-pin IC package. These are used for two purposes in the C64: to bank-switch the machine's read-only memory (ROM) in and out of the processor's address space, and to operate the datasette tape recorder. The C64 has 64 KB of 8-bit-wide dynamic RAM, 1 KB of 4-bit-wide static color RAM for text mode, and 38 KB are available to built-in Commodore BASIC 2.0 on startup. There is 20 KB of ROM, made up of the BASIC interpreter, the KERNAL, and the character ROM. As the processor could only address 64 KB at a time, the ROM was mapped into memory, and only 38911 bytes of RAM (plus 4 KB in between the ROMs) were available at startup. Most "breadbin" Commodore 64s used 4164 DRAM, with eight chips to total up 64K of system RAM. Later models, featuring Assy 250466 and Assy 250469 motherboards, used 41464 DRAM (64K4) chips which stored 32 KB per chip, so only two were required Since 4164 DRAMs are 64K1, eight chips are needed to make an entire byte, and the computer will not function without all of them present. Thus, the first chip contains Bit 0 for the entire memory space, the second chip contains Bit 1, and so forth. This also makes detecting faulty RAM easy, as a bad chip will display random characters on the screen and the character displayed can be used to determine the faulty RAM.
The KERNAL ROM went through three separate revisions, mostly designed to fix bugs. The initial version is only found on 326298 motherboards, used in the first production models, and cannot detect whether an NTSC or PAL VIC-II is present. The second revision is found on all C64s made from late 1982 through 1985. The third and last KERNAL ROM revision was introduced on the 250466 motherboard (late breadbin models with 41464 RAM) and is found in all C64Cs. The 6510 CPU is clocked at 1.023 MHz (NTSC) and 0.985 MHz (PAL), lower than some competing systems (for example, the Atari 800 is clocked at 1.79 MHz). A small performance boost can be gained by disabling the VIC-II's video output via a register write. This feature is often used by tape and disk fastloaders as well as the KERNAL cassette routine to keep a standard CPU cycle timing not modified by the VIC-II's sharing of the bus.
IC locations changed frequently on each motherboard revision, as did the presence or lack thereof of the metal RF shield around the VIC-II. PAL boards often had aluminized cardboard instead of a metal shield. The SID and VIC-II are socketed on all boards; however, the other ICs may be either socketed or soldered. The first production C64s, made in 1982 to early 1983, are known as "silver label" models due to the case sporting a silver-colored "Commodore" logo. The power LED had a separate silver badge around it reading "64". These machines also have only a 5-pin video cable and cannot output S-video. In late 1982, Commodore introduced the familiar "rainbow badge" case, but many machines produced into early 1983 also used silver label cases until the existing stock of them was used up. In the spring of 1983, the original 326298 board was replaced by the 250407 motherboard which sported an 8-pin video connector and added S-video support for the first time. This case design was used until the C64C appeared in 1986. All ICs switched to using plastic shells while the silver label C64s had some ceramic ICs, notably the VIC-II. The case is made from ABS plastic which may become brown with time. This can be reversed by using a process known as "retrobright".
After a redesign in 1983, the VIC-II was encased in a plastic dual in-line package, which reduced costs substantially, but it did not totally eliminate the heat problem. Without a ceramic package, the VIC-II required the use of a heat sink. To avoid extra cost, the metal RF shielding doubled as the heat sink for the VIC, although not all units shipped with this type of shielding. Most C64s in Europe shipped with a cardboard RF shield, coated with a layer of metal foil. The effectiveness of the cardboard was highly questionable and, worse still, it acted as an insulator, blocking airflow which trapped heat generated by the SID, VIC, and PLA chips. The SID was originally manufactured using NMOS at 7 micrometers and in some areas 6 micrometers. The prototype SID and some very early production models featured a ceramic dual in-line package, but unlike the VIC-II, these are extremely rare as the SID was encased in plastic when production started in early 1982.
In 2015, a Commodore 64 compatible motherboard was produced by Individual Computers. Dubbed the "C64 Reloaded", it is a modern redesign of the Commodore 64 motherboard revision 250466 with a few new features. The motherboard itself is designed to be placed in an empty C64 or C64C case already owned by the user. Produced in limited quantities, models of this Commodore 64 "clone" sport either machined or ZIF sockets in which the custom C64 chips would be placed. The board also contains jumpers to accept different revisions of the VIC-II and SID chips, as well as the ability to jumper between the analogue video system modes PAL and NTSC. The motherboard contains several innovations, including selection via the RESTORE key of multiple KERNAL and character ROMs, built-in reset toggle on the power switch, and an S-video socket to replace the original TV modulator. The motherboard is powered by a DC-to-DC converter that uses a single power input of 12 V DC from a mains adapter to power the unit rather than the original and failure-prone Commodore 64 power supply brick.
Raspberry Pi Zero has micro USB and mini HDMI inputs. This makes it harder to connect standart USB devices or standard USB HDMI cables to it. So I made a simple micro USB converter. I made this converter to align with the end of the HDMI port converter piece.