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SwitchTOS V1.0 |
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SwitchTOS is an adapter for switching between 4 operating systems for ATARI ST with 6 TOS ROMs, e.g. motherboard C070523-001 Rev C. Because the circuit consists of only a few standard parts and hobbyists should have a subset in stock, we do not offer a kit for the time being, but the PCB and individual parts.
The special feature of SwitchTOS is that the switching takes place with the reset button and therefore no switching elements are required on the housing. A permanent setting for a specific TOS is also possible with two jumpers.The 4 new TOS versions are stored in 256kB blocks one after the other in the flash (even if only 192kB are used each) and switched forward by one block with each keystroke, strictly speaking in the order 1-2-3-0 after cold start. A possible assignment would be e.g. TOS1.02 - TOS1.04 - EmuTOS - KaosTOS.
The schematics of SwitchTOS is simple, the difficulty with the 6 ROM motherboards is the limited space under the power supply. Headers cannot be used, SwitchTOS works with angled pins pulled of headers.
SwitchTOS is open source under the GPL license. The schematic will be published on Github. We do not offer a programming service for Flash, you can only buy the unprogrammed 4Mb Flash from us. For programming, for example, the well-known Willem programmer is suitable.
SwitchTOS is primarily intended for use with 192kB TOS versions, further modifications are required for 256kB TOS versions. The GLUE must not trigger a bus error at Exxx addresses, an address comparator (7485/74688) must recognize the Exxx addresses and drive the 256k signal in SwitchTOS, the solder jumpers on SwitchTOS must be reset (connect JP3, disconnect JP4).
TIP: Get to know the project first, then order. In particular, first find a source for the TOS versions, a programming option, then use the parts list to find the parts that are still needed.
| RefDes | Description | Value | Footprint | Approved parts | MPN | Webshop ID | Qty |
| Flash 512k x8 55ns | PLCC32 | Microchip SST39SF040-55-4C-NHE | SST39SF040-55-4C-NHE or | ||||
| PLCC32 | Microchip SST39SF040-55-4I-NHE | SST39SF040-55-4I-NHE or | |||||
| U20, U50 | Flash Memory | Flash 512k x8 70ns | PLCC32 | Microchip SST39SF040-70-4C-NHE | SST39SF040-70-4C-NHE or | 8088 | 2 |
| PLCC32 | Microchip SST39SF040-70-4I-NHE | SST39SF040-70-4I-NHE | |||||
| U20, U50 | Flash Memory Socket | PLCC32 SMT | PLCC32 | Multicomp MC-32PLCC-SMT | MC-32PLCC-SMT or | ||
| PLCC32 | Preci-Dip 540-88-032-17-400 | 540-88-032-17-400 or other | 8099 | 2 | |||
| SO14 | NXP 74HC11D | 74HC11D | |||||
| SO14 | TI CD74HC11E / SN74HC11D | CD74HC11E / SN74HC11D | |||||
| U1 | AND Gates | Triple 3-Input AND | SO14 | NXP 74HCT11D | 74HCT11D | 7085 | 1 |
| SO14 | TI CD74HCT11M | CD74HCT11M | |||||
| U40 | Binary Counter | 12-Stage Binary Counter | SO16 | FSC/OnSemi MM74HC4040M | MM74HC4040M | 7592 | 1 |
| for switching by reset button | SO16 | TI CD74HC4040M | CD74HC4040M | ||||
| Pins RA for wire connectors and jumpers only | for wire connectors and jumpers only | 40 pos 0.1” header RA | any, for wire connectors and jumpers only | Header_2.54mm_male_1x40_RA | 7713 | 1 | |
| Pins RA for Atari sockets U2/U5 | for pin extraction only | 80 pos double-row 2mm header RA | any, for pin extraction only | Header_2mm_male_2x40_RA | 7714 | 1 | |
| Wire | SwitchTOS Wire Set | SwitchTOS Wire Set | SwitchTOS Wire Set | 8090 | 1 | ||
| PCB | PCB SwitchTOS (first batch named MultiTOS) | PCB SwitchTOS | PCB SwitchTOS V1.0 | 8089 | 1 |
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