17 Apr
2012
17 Apr
'12
9:22 p.m.
On 4/17/2012 6:56 PM, David Griffith wrote:
Who was the one with the wacky idea of building a Straight-Eight PDP8
using flipchip cards populated with surface-mount parts? I have a
hankering to run some numbers about it.
I have a PDP8 in an FPGA that can be configured as a Straight-8.
It's about an inch on a side. That includes 32Kx12 memory,
3 serial ports, EAE, RTC, and a disk controller that is register
compatible with an RK8E. It emulates 4 RK05 disks on a Secure
Digital (SD) memory card. That adds another inch-and-a-half
or so of board area.
You'll need RS232 buffers, a crystal, and it needs a bit of a
power supply.
The PDP8, a VT100 terminal (VGA and PS/2 KBD), and a connector
for all the front panel switches and lights all fits on a
2.5 x 3.8 inch circuit board.
I just got it booting OS/8 the other night - BASIC, FOCAL, and
PAL8 all run from OS/8. (It does crash running my favorite
program /advent/ - so something ain't right. If anybody
has any debugging suggestions - contact me off list!).
I have models for all of the IO including the SD card so I can
boot OS/8 to the 'dot prompt' in the logic simulator in a
couple of minutes. GHDL is even faster.
Even *if* you decide to do flipchips with SMT parts, you may want
to consider prototyping with an FPGA. I can recompile the design
and load it into the target in less time than I can move a wire-
wrap wire.
Rob.