![]() "Big Box" models allowed for a different type of memory to be installed, known as Fast RAM, where fast means that it's dedicated to the main processor, so that it doesn't have to compete with the other chips in order to gain access to it (as is the case with Chip RAM). Most low-end Amiga models only came with Chip RAM. Strobe for identification of long horiz lineīlitter pointer to source C (high 5 bits, was 3 bits)īlitter pointer to source C (low 15 bits)īlitter pointer to source B (high 5 bits, was 3 bits)īlitter pointer to source B (low 15 bits)īlitter pointer to source A (high 5 bits, was 3 bits)īlitter pointer to source A (low 15 bits)īlitter pointer to dest D (high 5 bits, was 3 bits)īlitter start and size (win/width,height)īlitter control 0, lower 8 bits (minterms)īlitter V size (for 15 bit vertical size)īlitter H size and start (for 11 bit H size)Įxt.OpenAmiga500FastRamExpansion is an Open Hardware 4/8 MB Fast RAM Expansion for the Commodore Amiga 500 Computer. Strobe for horiz sync with VB (vert blank) Write to all 4 joystick-mouse counters at once Pot count start,pot pin drive enable data ![]() Pot counter data right pair (vert, horiz) This bit is automatically resets (=0) when underflow occurs during one-shot mode.Īll unused register bits are unaffected by a write and forced to 0 on a read. This is a strobe input, there is no data storage bit 4 will always read back a zero and writing a 0 has no effect. Timer B counts Timer A underflow pulses while CNT pin is held high. Serial port=output (CNT is the source of the shift clock) Serial port=input (external shift clock is required) Reading TOD registers always reads TOD clock, regardless of the state of the Alarm bit. Note: CIAA can generate interrupt INT2 and CIAB can generate interrupt INT6. Most CPU-socketed - and Amiga 1200 - turbocards maps their RAM here.įrom here, it is the "negative" address space the CPU can see it and can use it, but the OS can not.ĭirection for Port A (BFE001) 1=output (set to 0x03)ĭirection for Port B (BFE101) 1=output (can be in or out)ĬIAA Timer A low byte (7.15909 MHz NTSC 7.09379 MHz PAL)ĬIAA Timer B low byte (7.15909 MHz NTSC 7.09379 MHz PAL)ĥ0/60 Hz event counter bits 7-0 (VSync or line tick)ĬIAA Serial Data Register (connected to keyboard)ĭirection for Port A (BFD000) 1 = output (set to 0xFF)ĭirection for Port B (BFD100) 1 = output (set to 0xFF)ĬIAB Timer A low byte (7.15909 MHz NTSC 7.09379 MHz PAL)ĬIAB Timer B low byte (7.15909 MHz NTSC 7.09379 MHz PAL) You have to modify the machine to be able to use the entire 64 MB area. Memory can be mapped here too, but if you have some hardware which maps something here, it will collide.īy default, the hardware can only handle the last 16 MB of it. On the A4000, the first 1 MB contains the Chip shadow registers.Ī600 & A1200 PCIMCA and IDE configuration registersĪ3000 SCSI controller / A4000 IDE controller / A1200 DMA controllerĬDTV & CD32 Extended ROM / A4000 Diagnostics ROM Technically this is Fast RAM, because only the CPU sees it, but due to it's speed, it is called "Slow RAM", but real Fast RAM can too be mapped here, as the ACA500 does it. Zorro 2 IO expansion / Additional KickStart expansion (A1200)Ī500 "Trapdoor" Slow RAM / A4000 Chip shadow registers Zorro 2 IO expansion / PCMCIA PC I/O (A600 & A1200) Zorro 2 IO expansion / PCMCIA bits (A600 & A1200) Zorro 2 IO expansion / PCMCIA I/O (A600 & A1200) Zorro 2 IO expansion / PCMCIA attributes (A600 & A1200) In the A1200 and A600 you can have 4 MB Fast RAM + 4 MB PCMCIA RAM or 8 MB FastRAM. Upper AutoConfig Zorro 2 Fast RAM / PCMCIA RAM (A600 & A1200) Only ECS / AGA Amigas (only Big Fat Agnus / Alice)Īmigas containing Big Fat Agnus and Alice can see a further 1 MB of Chip RAM. Amiga memory map Address space Address spaceįrom "new" OCS Amigas (at least Fat Agnus)Īmigas equipped at least with Fat Agnus can address further 0.5 MB of Chip RAM.
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