Given 16 bit wide ROMs, I would expect the microcode width to be rounded up to
a multiple of that, so 64 bits, which means the expected ROM size is 64k bits.
That matches two of the ROMs you mentioned.
paul
> On Feb 7, 2023, at 12:25 PM, Lars Brinkhoff via cctalk
> <[email protected]> wrote:
>
> Hello,
>
> I could use some help making sense of the VAXstation ROM images.
> A set is provided here: https://www.9track.net/roms/
>
> The two .bin files are each one halfword of a 16-bit wide ROM for the
> 68000 display processor. I checked it, and it's fine.
>
> My problem is with the Bit Blit Accelator. The board has four Am2901
> bitslice processors to make up a 16-bit custom blitter. The information
> I have is that the microcode is 57 bits wide and there should be 1024
> words. However, this is not a great match for the rest of the ROM
> images.
>
> Some of the BBA ROMs seem to be bit masks, presumably useful for
> rendering graphics. But none of them seem to match what I'd expect to
> see for a 57x1024 microcode.
>
> Here are the sizes, in bits, of the ROMs:
>
> Bit Blit Accelerator (BBA)
> 23-066K3.jed 2048
> 23-067K3.jed 2048
> 23-068K3.jed 2048
> 23-069K3.jed 2048
> 23-076F4.e32 16384
> 23-077F4.e65 16384
> 23-077J5.jed 2048
> 23-078J5.jed 2048
> 23-354A1.e33 256
> 23-355A1.e66 256
> 23-356A1.e77 256
> 23-357A1.e85 256
>
> Display Processor Module (DPM)
> 23-020L1.jed 3553
> 23-021L1.jed 3553
> 23-022L1.jed 3553
> 23-023L1.jed 3553
> 23-024L1.jed 3553
> 23-025L1.jed 3553
> 23-288E4.bin 65536 68000 code in these two.
> 23-289E4.bin 65536
