This board family is the original GVP Impact (Series I) SCSI controller and RAM expansion technology for the Amiga 2000. It is based upon a 33C93 8-bit SCSI controller that can DMA transfer data to/from an onboard 16K SRAM buffer, which is then serviced by the CPU. The board has an internal 50-pin SCSI header and an external DB25 interface. SCSI bus termination (resistor packs) are soldered in.
There were 2 x PCB revisions of this product which supported slightly different memory configurations. The first revision supported a 0M/1M/2M configuration with 8 or 16 pieces of 256x4 DIP RAM chips. The second revision only supported 0M/2M configuration with 16 pieces of 1Mx1 DIP RAM chips. Memory chips should be 100ns or faster. The first revision (256x4) had a PAL update that was necessary to correct an AutoConfig bug with the 1MB memory setting. GVP 1.0 (2), 2.x (2), and FastROM 3.x (1) AutoBoot ROM(s) are supported under Kickstart 1.3 and higher.
There are jumpers for Autoboot ROM disable (remove J4), RAM settings, and a factory test (J3 = Stop AutoConfig if On). All others jumpers are reserved: J5 is a test jumper, and shorting disabled the on-board SRAM. J6/7/8 on the second generation board were intended as software-readable bits which were nevver used (and U50 was not included). This board was eventually superseded by the GVP Impact SCSI+RAM 8/0 product that used standard 30-pin SIMM modules. J3 disabled AutoConfig at the board for testing purpoes, disabling downstream expansion in the process. There is no on-card HDD activity LED header.
The D1 diode just below the 33C93 chip was found to be frequently burned out as extrnal devices with dissimilar PSUs (to the Amiga's) sometimes back-fed power on the TrmPwr line. This resulted in GVP leaving the part off the board in later SCSI controller products.
The original 2/x board has the (oops) Vendor ID of 1761 / 8 for the 1MB or 2MB RAM AutoConfig, and the proper Vendor ID of 2017 / 3 for the 128K PIC SCSI interface. Feedback on the later 1MBx1 2A version's AutoConfig details are wanted.
Jumpers for the 256x4 DRAM card Memory:
0MB - J1-on, J2-on
512K - J1-off, J2-off (undocumented/tested)
1MB - J1-on, J2-off
2MB - J1-off, J2-on