Jumpers J351: DF1 Enable Closed: Enable double-density (880K) floppy as DF1. Open: No DF1 or for high-density (1.76M) DF1. J852: Fast RAM SIMM Size (Chip RAM is always 2M.) 256K: 1M SIMMs. 1M : 4M SIMMs. CN404: Internal Audio Connector Audio signals attached here will be mixed with the A4000 audio output. The A4000 audio is somewhat louder than the normal line level output from most CD-ROM drives, presumably to make sound effects audible over background music. Setting the software- controlled A4000 audio level lower (to 32 instead of 64) will help match the levels. Pin 1: Audio In (Left) Pin 2: Ground. Pin 3: Audio In (Right)
„Mystery“ Header (courtesy of Dave Haynie)
„There is a 12 pin header (DIL, J975) near the mouse ports. This feeds the 'extra' shift register in Lisa. Unlike OCS/ECS systems, which simply multiplex the four quadrature signals from each mouse port with one another, the AA systems serialize all eight bits of mouse data. While they were at it, the AA designers added a second 8-bits to the mouse port registers. These don't hook into mouse logic or anything, but they can be read by the CPU.
So we used them for configuration. The first two bits (not on that header) tell the OS about the AA system – is it 16 or 32 bit, is it single or double access per cycle. These are hard-wired on the motherboard. The remaining six bits read high when unjumpered, low when jumpered. I had recommended using one to say 'VGA only,' but there wasn't enough ROM space.“
Other Jumpers (Not Shown Above) J100: CLK90 Clock Source 1-2 Closed: Internal (68020/68030) 2-3 Closed: External (68040) J104: CPU Clock Source 1-2 Closed: Internal 2-3 Closed: External J151: ROM Speed: 160 or 200 ns ROMs. 1-2 Closed: 200 ns ROMs (default). 2-3 Closed: 160 ns ROMs. J213: Chip RAM: 2M or 8M 1-2 Closed: 2M Chip RAM (default). 2-3 Closed: 8M Chip RAM. This option was apparently for use with the never-released AAA chip set, and won't work in a normal A4000. J500: Sync On Green 1-2 Closed: Sync on green disabled (default?). 2-3 Closed: Sync on green enabled (see the Common Problems section for the Green Display Problems note on this jumper). J501: Lisa Sync (Wide input on the Lisa chip.) 1-2 Closed: CSync from Agnus Pin 80. 2-3 Closed: +5V (default). J502: Select DAC Sync 1-2 Closed: DAC syncs on green. 2-3 Closed: DAC uses standard signal (default). J850: Enable DSACK (Used with 68020) 1-2 Closed: DSACK Enabled for 68020. U860 and U152 also required. 2-3 Closed: No DSACK.
„Haynie Kludge“ Jumper (courtesy of Dave Haynie)
„That jumper enables the „early sizing“ mode on the Zorro-3 bus. One of the complaints about Zorro-3 is that the size of a transfer isn't known until the data phase of the cycle. So in the Zorro-3 addendum I added an optional mode that allows data size information to be latched in the address phase. Just in case any existing boards have a problem with this (if they go by the spec, they don't, but who really knows what they're doing), it's shipped disabled. The idea was to test this out in the A4000T, bless it as standard for future Zorro-3 controllers as long as it did what designers wanted.“
Amiga 4000 Desktop Jumper Settings Fucntion: Jumper: Setting: Description: CLK90 Clock Source J100:1-2 X-X X Internal (020/030) J100:2-3 X X-X External (040) CPU Clock Source J104:1-2 X-X X Internal J104:2-3 X X-X External ROM Speed J151:1-2 X-X X 200ns J151:2-3 X X-X 160ns CHIP RAM Size J213:1-2 X-X X 2 Meg J213:2-3 X X-X 8 Meg (yeah right) Enable Second J351:1-2 X-X No Second internal floppy drive Internal Floppy or 1.76MB floppy drive J351: X X Enable second internal floppy drive 880k as DF1: Redirect DF0: J352:1-2 X-X X Internal: DF0: and DF1: internal DF2: and DF3: external External: DF2: and DF1: internal DF0: and DF3: external Enable DSACK J850:1-2 X X DSACK enable. Required if CPU is a 68020. Also requires U860 and U152. J850:1-2 X-X No DSACK. RAM Size J852:1-2 X-X X RAM size 1 Meg x 32 J852:2-3 X X-X RAM size 256k x 32 Select NTSC/PAL J212:1-2 X-X X Select NTSC J212:2-3 X X-X Select PAL VBB\MA10 J214:2-3 X X-X Supplied VBB to ALICE J214:1-2 X-X X ALICE supplies MA10 for 8 Meg CHIP (NO it DOESN'T WORK!) Select Sync on Green J500:1-2 X-X X Sync on Green Disabled J500:2-3 X X-X Sync on Green Enabled LISA Sync J501:2-3 X X-X Default Select DAC Sync J502:1-2 X-X X DAC Syncs on Green J502:2-3 X X-X DAC used standard signal