Amiga 1000
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(pictures copyright by M.A.Grundke)
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A1000 type plate:
C= commodore
AMIGA™ 1000
PERSONAL COMPUTER
Serial No. XM 4121242 |
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A1000 keyboard type plate:
C= commodore
KEYBOARD FOR AMIGA™ 1000
French/Belgian Version
Serial No. MT 0003653 |
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| A closer view on the A1000's keyboard. As already mentioned in the specifications table, this particular keyboard is a relabeled French/ Belgian version (also see the keyboard serial number above). On this picture, you can easily spot the relabeled keycaps (e.g. all number keys, Q, W, A, Y, Z etc) for creating the german QWERTZ (i.e. DIN) layout. However, relabeling machines' keyboards was not unusual for Commodore (e.g. when there was no localized version available yet) |
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Amiga 1000 board-overview (with floppy drive and PCB shield removed):
as mentioned earlier, this is the third revision of the Amiga 1000 board, without daughterboard and configured for PAL-output. Left you can see part of the internal PSU (power supply unit), with its big fan at the machine's back - it's a Mitsumi SR68-05550M, by the way. Right from the PSU, in the middle of the board are Denise (U4A), Agnus (U4C) and Paula (U4F). Directly right from them a 'field' of 8 pcs. 74LS244, perhaps memory address logic, because below them (extending from the PSU to the middle of the board) is the machine's RAM bank. 512 KBytes consisting of 16 pcs. 64Kx4
(U1B-U1M and U2B-U2M). Half of that RAM, by the way, is used as WOM to store the Kickstart. Moving right, again, there are several 74xx with the board's silk-screening below them and the two controller ports to their right. Note that this normally is the location of the floppy drive. Moving up from here, are the expansion port (machine's right side) with the big CPU (U6U) next to it. Left from are the two 8520 CIAs (U6S and U6T) and below them the two A1000 OS ROMs (U5N, U5S) with empty soldering pads for another two (U5T, U5R). Moving up again and a little left, there's the board's PSU connector with a shielded 'cage' above it (with five 74xx and an oscillator within) - must have something to to with video output. Interesting is the low integration density of the board, compared to that of later machines (like the CD³²) |
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board silkscreening:
MADE IN JAPAN Y8AG1034488 REV.B
PART NO 252277-01 86.08.08 |
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| The CPU that had been used in A1000, A500 (Plus), A2000, A600 and CDTV: the Motorola 68000, here in OEM-manufactured version as Rockwell R68000P8. Behind it the expansion-port. In the later A500/ A500 Plus, that port was turned by 180 degrees so that you needed an adaptor to connect A1000-expansions like the CBM 1060 'Sidecar'. Who knows why... |
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| The MOS 8367 was the second representative of the 'Agnus'-family, allowing 512 KBytes ChipRAM (an improvement compared to its ancestor, which could only access 256 KBytes ChipRAM). ChipRAM and FastRAM are divided in the Amiga-design so that the CPU can access 'its own part of RAM' (=FastRAM) at full speed, whereas the coprocessors Denise, Agnus and Paula have to share ChipRAM to store their data. Like all earlier Agnuses, furthermore, MOS 8367 cannot be PAL/ NTSC-switched; it can only do PAL. For NTSC, MOS 8361 was the
appropriate counterpart. This is interesting because later Agnuses were both PAL- & NTSC-capable |
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| The A1000's RAM bank, consisting of 16 pcs. 64Kx4 DRAMs (here 'mixed', i.e. 10 pcs. Hitachi HM50464P-15 and 6 pcs. NEC D41464C-15). 'Hey', you will think, 'that makes a total of 512 KBytes!' Yes, it does, but only 256 KBytes of that can be used as ChipRAM. The other 256 KBytes store the Kickstart after it was loaded from disk, and are then write-protected (I wonder how they did that without MMU - just switching off the write signals?). That part of RAM is called the WOM (see 'ROM' below) |
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The two A1000 bootstrap-ROMs, C252179-01 and C252180-01. These ROMs contain the code that loads Kickstart from disk when the machine is powered on. It is then stored in additional 256 KBytes RAM on the board, protected from overwriting (that's why this part of memory is sometimes called 'WOM', 'write once memory'). Although loading a Kickstart from disk takes time, it can be quite useful if you often need to change versions (like the developers did). However, the A1000's WOM can only store 256KB Kickstarts, of course, so Kickstart 1.3 is the last version usable (or at least without modification to the machine). Note the soldering pads for another two ROM sockets here. Perhaps they are remnants of plans to use bigger OS ROMs (like a real
Kickstart ROM), or they were just added to the board design for flexibility |
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| This is the machine's keyboard controller, the MOS 6570. It was used in all OCS- and ECS-Amigas. In the A1200 it was then replaced by the CBM 391508-01 keyboard-MPU (basically the same but PLCC, integrated on the board and with less power consumption) |
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| MOS 8362 'Denise' was impressive when introduced in 1985. 4096 colors (even at once, in the so-called 'Hold-And-Modify' mode) and a maximum resolution of 640x512 pixels (although interlaced) made the Amiga a revolution - only the most expensive workstations were capable of that, these days. An interesting detail, however, is that some earlier A1000s lacked the EHB mode ('Extra Half Bright', 64 colors using halftones) because it was simply missing in an early Denise-revision. Not really a problem, since it was rarely used anyway, and Denise could easily be replaced by a never revision chip. Also interesting to know is that the HAM-mode was first
called 'Hold-And-Control', and later renamed to 'Hold-And-Modify'. As the name implies, the basic concept behind this mode is that a pixel's color can be 'held', and will be modified for use with the next pixel (i.e. altering its RGB-levels). This way, only 6 bit are needed for a total of 4096 colors, which would normally require 12 bit. Slight disadvantages were the limited possibilities when choosing the next pixel's color, and the slow drawing speed. So this mode was mostly used for digitized pictures - only very few games made use of it (such as Links, the golf simulator). As Jay Miner had once pointed out in an interview, HAM was initially added as an experiment, and was then kept as a nice feature |
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| MOS 8364 ('Paula'), the Amiga-soundchip that has never been changed in the whole Amiga-series! It has four independantly usable sound-channels (8 bit), which can be combined to two 16 bit stereo channels. Although that was more than impressive when the Amiga was introduced on Winter CES 1985, it couldn't compete to the PCs and workstations in later years |
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| The two MOS 8520R3, responsible for the Amiga 1000's I/O-functions (also found in the later Amigas, sometimes in modified versions or arrays). These CIAs are quite similar to the MOS 6522 'VIA' used in many classical Commodore-machines like the VC-20 |
Also see the developer's signatures (imprinted in most A1000)
