pat_at_cart-server.purdueriots.com wrote:
>
> In a project I'm thinking about starting this summer, I want to try and
> re-create a PDP-11 (or maybe a -8 or something) using either SSI logic
> and/or PAL/GALs. I would like to do the entire thing in SSI, but I fear
> that I'd quickly eat up a lot of money on the project, so where necessary
> I'd replace sections with PALs. Anyone have any good ideas?
(snip)
> 1) CPU card
> 2) Memory - SRAM
> 3) Front-panel switches
> 4) Console serial port
> 5) A few digital I/O ports
> 6) Floppy interface (anyone suggest an easy to interface controller?)
> 7) IDE controller
Barring #7 can I sell you the nice 12/24 bit FPGA cpu I homebrewing. :)
The PDP-11 is way too complex for SSI logic. A reduced PDP-8 style cpu
would be possible with SSI logic. While not true SSI logic modern
EEPROMS would be very useful for control logic. Byte magazine had a few
TTL designed cpu's. Stack based languages like Forth are easy to do in
TTL. I would have done my FPGA computer in TTL but nowadays you can't
find the 74LS chips I needed anymore like 74ls382 4-bit alu. One other
option is 2901 bit slice parts. B.G.Micro seems to have a few in stock.
If I were to redesign I would use 2901 bit slice parts and EEPROMS for
control now that I know where to find 2901's.
A floppy disk controller interface is fairly simple but you need a fast
CPU for the disk if some sort of DMA is not used. That is why my FPGA
computer is not quite finished , I am squeezing in DMA for HD floppies.
Also the front panel logic needs a bit of work too.
If you really want to be authentic don't forget to add Refresh logic on
the CPU for DRAM.
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html
Received on Sat Apr 06 2002 - 11:39:22 BST