Mini Expander for Video Genie System EG3003, Dick Smith System 80 (TRS-80 clone)

Description: The RetroTik card faithfully emulates the original Expander EG3013/3014, including diskette drives for the Video Genie System EG3003 (TRS-80 clone). The main motivation behind the creation of this card was to enable a fully-fledged and comfortable study of the development and capabilities of the original disk operating systems of these computers, from their very beginning. Several disk operating systems and a large amount of software were created for these legendary personal computers in the late 70s and early 80s. Although there are many great software emulators for these computers, they cannot replace the experience of working on a real computer (I really know what I'm talking about). Without an Expander (primarily a floppy drive controller) and diskette drives, it's really impossible. That's why this alternative card was created. So the goal was to develop as small as possible a period expansion card that will faithfully and reliably emulate the Expander on the hardware level, including the diskette drives connected to it. The basic functions of this card are: HW emulation of the FD1771 disk controllerImplementation of floppy disks in the form of ROM/RAM memory chipsExpansion of the computer's operating memory by 32 kBGeneration of all necessary interruptsPrinter interface (add-on module)Interface for synchronous serial communication (add-on module)HW emulation of the FD1771 disk controller The original expander was equipped with one of the first chips from Western Digital, the FD1771. This chip had implemented some functions (properties) that did not appear in later controllers, so it was difficult to simply replace it in the future. Our card aims for full emulation on the logical (sector) level, so that the necessary compatibility is achieved. Conversely, on the side of the emulated FD1771 floppy disk drive, an interface for ROM/RAM memory chips replacing old floppy disks is implemented. At first glance, it might seem that these are classic ROMdisks and RAMdisks, but in reality it is much more complicated. Although we don't have a physical recording magnetic layer and therefore we don't have to worry about it, on the other hand, we lack this layer for the proper functioning of the controller. As a result, all commands (functions of the original controller) except "Read Address", "Read Track", "Write Track" were implemented. These functions are primarily used for physical formatting and low-level copying of diskettes, which in our case is not interesting. Primary compatibility is verified on the major disk operating systems TRSDOS 2.3, NEWDOS/80 2.0 and LDOS 5.3.1 in versions designed for the Model I. Of course, programs with direct access to the controller also work, but the above 3 low-level commands cannot be used. Implementation of floppy disks in the form of ROM/RAM memory chips The card has two 40-pin sockets with so-called zero-force insertion (equipped with a lever). These are intended for ROM (EPROM) chip disks, i.e. permanently Read Only. The sockets are intended only for circuits in DIL32 packages and accommodate chips of size 128, 256 and 512 kB (for example 27100, 272001, 274001). Chip disks (memory) can be replaced during operation, you just have to wait until no disks are read from or written to (activity can be seen on the fitted signaling LEDs). Having access to an EPROM programmer and a UV eraser is ideal. The other two standard sockets are intended for permanently backed-up RAM (SRAM) and are equipped as standard with a circuit (chip) with a capacity of 512 kB. The internal installed battery lasts at least 10 years with this connection, but in our other solutions these batteries have been working for over 30 years and still have enough energy and voltage to back up similar SRAM memories. The circuit around this memory is important, which guarantees high resistance and protection of the contents during sudden voltage changes (typically power up and sudden power off). For example, if you are writing and there is a power failure, then at worst the writes will not complete and only the currently written apartment will be left in an unknown state. Without this circuitry repeated testing with intermittent power led to other bytes being occasionally accidentally overwritten, albeit with a very low probability. After completing the circuit wiring, there were no accidental overwrites during repeated tests. Each physical position (memory) can be set (jumper): assign logical address (:0,:1,:2,:3)single-sided or double-sided floppy disk formatfor single-sided disks, set the currently selected sideset Read Only signalling for the controller (similar to the classical taping over of a viewport)only with RAM chips it is possible to physically disconnect the WRITE signal and then it becomes Read Only memory in every state ROM/RAM chip disks have their geometry (format) determined by connection and jumper settings, but their maximum sizes are: for single-sided floppy disks: a maximum of 16 sectors of 256 bytes per track and a maximum of 128 tracks in totalfor double-sided floppy disks: a maximum of 2x16 sectors of 256 bytes per track and a total of a maximum of 64 tracks The maximum total capacity of a floppy disk is 16 x 256 x 128 (or 32 x 256 x 64), i.e. 524,288 kB. The real capacity is given by the chosen geometry given primarily by the DOS, so at 10 sectors of 256 bytes and at 80 tracks it's 204,800 kB. It is therefore optimal to choose a format with 16 sectors per track and side. But even in the case of a less efficient geometry, it will be possible to use the unused sectors. Our mini Expander was developed to fulfill several essential requirements: faithful emulation of the original Expander EG3013/3014 including four floppy drivesoriginal period design (diagram, components and own production correspond to the early 90s), so that this piece of hardware can be placed and operated in a museum, retro lab without disturbing the authenticitycompact and mini design enabling the mini Expander to be placed directly on the upper flat surface of these computers, which we will use for demonstrations, seminars, but also for the possibility to borrow the set for study the possibility to power directly from the old computer via the expansion connector. This requires limiting the long-term consumption below 2W. If you like compact minimalistic solutions, then every extra component breaks it. On the other hand, not only the original rectifier diodes in the power supply of these computers will have a certain degree more (about 2 to 3 degrees Celsius you will measure a higher temperature on the cooler of the 5V stabilizer - 7805) Putting all these requirements together was not quite so simple, as evidenced by the total time of development and testing, which eventually exceeded the originally planned period of six months. Several major decisions had to be made during development, and one of those decisions was whether to place a communication port on the mini Expander, and if so, which one. The complexity of the overall emulation of the FD1771 controller proved critical, considering the capabilities of the first programmable gate arrays of the time (limited amount of programmable logic and limited number of pins). In the final it was clear, either serial or parallel port, both at the same time cannot be implemented. The choice of a serial port was clearly driven by the need for data backup and recovery. On the other hand, the need for presentations and personal demonstrations of the use of the computer spoke for choosing a parallel port, where the printer has always been its basic peripheral, without which it doesn't make much sense. Of course, it's always possible to implement ports as standalone extensions, but that was against the intent of a compact solution. In the end, the parallel port won out. There were several reasons for this, but the possibility of a full-fledged implementation of the interface for the printer while maintaining the necessary size and power supply options proved to be essential. But what about serial communication, without which data cannot be backed up or restored? There is nothing to worry about, our mini Expander really only decodes/addresses for the parallel port, but its design allows you to install an expansion module (board) with a parallel port or an expansion module (board) with a serial interface, but in a slightly different form than you are probably used to. For standard serial communication, in addition to the address decoder, we need a suitable clock (crystal oscillator), implement a UART-type circuit and, of course, obtain the necessary voltage, typically +-6V to +-12V. And that was already beyond the possibilities of programmable circuits, the required size of the mini Expander, but also the possibility of limited power supply directly through the expansion connector (expansion) of these old computers. The delivery includes: 1x custom card CZRT-VG3-01031x flat cable for connecting the card to the old computer (direct connector with 50 pins)1x box for the card printed on a 3D printer (including feet, necessary posts, screws and a set of cables with switches)1x set of period disposable rubber feet only for card variant without box1x module for synchronous serial communication1x module for connecting the printer via a parallel cable1x flat cable terminated with a CANON 25-pin male connector (for connecting a printer cable or a modem cable for serial communication)1x ROM disk (EPROM/ROM) with RetroTik utilities: a) for initializing, copying and erasing chip disks b) backup or restoration of individual files c) backup or recovery of the entire chip disk d) mini Expander diagnostics (only when booting from the given chip disk)1x ROM disk (EPROM/ROM) with LDOS 5.3.1 in geometry for large disk formats (or NEWDOS/80 or TRSDOS if you own the original license) The software for the superior communication computer is gradually being developed and can be downloaded from our product website. Manufacturing method: The printed circuit board marked CZRT-VG3-0103 (the base of the mini Expander) has a lead HAL (SnPb) surface treatment, and naturally lead tin is used when mounting it. The main reason is the fitting of period components and the use of period production technology. This is probably the only option to really produce quality products, even if we use new (unused) period components, often more than 30 years old. All production, including printed circuit board production, takes place here in the Czech Republic. We always thoroughly test all period components before installation, and we always use the manufactured card intensively for several days and repeatedly test it. Nevertheless, in principle we only have to provide a limited warranty precisely because of the use of period components. However, our long-term experience with the use of period components and period production is very good. If the user has any doubts about the functionality, our diagnostics is a great helper. Terms of use: The goods can only be used indoors and in a dry place. Temperature from 0°C to +70°C (not valid for a box printed on a 3d printer). Relative humidity maximum 80% non-condensing. Do not modify the connection of the custom card CZRT-VG3-0103 in a way other than that indicated in the instructions for use. Limited Warranty:the possibility of returning goods within 30 days of receipt (shipping costs are paid by the buyer)free support in the form of our product website or via e-mail communication until at least the end of 2029warranty is only on custom card CZRT-VG3-0103 (including two expansion modules)warranty is NOT on: accessiories, cables and other supplied partsin the event of a technical defect, repair for a period of 2 years from delivery for the cost of transporting the goods to us for service and sending them back, which is paid by the buyer. However, these service conditions do not apply to cases of mechanical damage to goods, in non-compliance with the terms of use or damage caused by overvoltage or reverse polarity of the board's supply voltage

Price: 495 USD

Location: Milevsko

End Time: 2024-12-22T11:00:00.000Z

Shipping Cost: 72 USD