Floppy Drive Deep Dive

1541 Memory Map 1571 Memory Map 1581 Memory Map ‘Boost Your 1571’ Memory Map DOS sector layout HW Bit Timing Byte Ready Sync Pinout Port A VIA1 Data Register Port B VIA1 Data Register Port B VIA2 Data Register Auxiliary Control Register Peripheral Control Register Interrupt Flag Register Interrupt Enable Register Port A CIA Data… Read more Floppy Drive Deep Dive

6522 Fast Serial Driver

INTRODUCTION FLOPPYmate requires a high speed data transfer to read/write an entire track within a single disk revolution. This task requires a data transfer rate of at least 40KB/s. High speed (>8 KB/s) data transfer from or to a 1541 Disk Drive is commonly achieved using a 8 bit parallel cable connected to Port A… Read more 6522 Fast Serial Driver

C64 PLA Replacement

INTRODUCTION Troubleshooting a dead C64 often reveals a faulty PLA IC as the root cause. The PLA does the address decoding and bank switching. SIGNETICS 82S100 (later PHILIPS PLS100) Bipolar Programmable Logic Arrays were used in early revisions of the C64 Mainboard assy, which were then replaced by MOS 8700-001 and MOS 906114-01. This blog… Read more C64 PLA Replacement

C64 MOS 8701 Replacement

INTRODUCTION The C64 can only work properly with stable clocking. In a C64 II the MOS 8701 IC generates two major clocks and maintains the fixed frequency and phase relationship. COLOR_CLK is the main crystal oscillator clock and DOT_CLOCK is derived thereof. This blog presents a replacement circuit for the MOS 8701 IC. Orginal MOS… Read more C64 MOS 8701 Replacement