16 Dec
2001
16 Dec
'01
2:17 p.m.
On Sun, 16 Dec 2001, Ben Franchuk wrote:
"Peter C. Wallace" wrote:
PALs were certainly available earlier, just expensive,
non-reprogramable, and power hungry. I think we used our first
programmable logic in 1986 (Altera EP900s and EP320s - both low power) for
emulation of some PC motherboard stuff in our low power V40 based embedded
PCs. We never used PALs but have used GALs a lot for simple decoders and
random logic. At about $.50 now they are hard to beat.
I think I would do most non-common (probably not Ethernet, USB or
video) I/O these days with FPGAs. Its great to be able to change the
function and pinout with just a downloadble config file. A 100K (Well
maybe 15K if you remove Xilinx inflation factor) SpartanII chip is only
$19.00...
On Sun, 16 Dec 2001, Richard Erlacher wrote:
I never heard about pal's until about 1990. In some ways the peripheral
chips are in a really sorry shape. You have vintage slow I/O (2 MHZ?)
or PC motherboard chip sets. Nothing in between. On my FPGA I can run
with a 250 ns memory cycle, but need to stretch it to 625 ns for I/O. I disagree that it's a mess. I haven't
looked at the requirements for a Z80
peripheral since the early '80's, but I can assure you that I'd dispose of
any
1st year engineering intern who couldn't whip up a suitable PAL or equivalent
MSI/SSI logic to handle the generation of properly timed inputs to the thing in
an hour or less.
Sure its trivial to do now but we were talking 1981 when PALS were
expensive.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html
Peter Wallace
Mesa Electronics