16 Dec
2001
16 Dec
'01
10:45 p.m.
Rochester isn't cheap, but they listed the PLCC-44 parts at $18.10, IIRC. The
last time I bought a WD controller (1979), it cost over $90, so the sticker
shock isn't an issue.
----- Original Message -----
From: "Ben Franchuk" <bfranchuk(a)jetnet.ab.ca>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, December 16, 2001 5:27 PM
Subject: Re: MITS 2SIO serial chip?
you
Richard Erlacher wrote:
> Why? The WD37C65 is a much easier part to use, and it programs pretty much
like
> a NEC uPD765, drives the cable directly, and
automatically deals with the
> data/clock separation for 500 KHz, 250 KHz, and 125 KHz data rates at both
300
> and 360 rpm. You can lift 'em from broken
HDC's or order 'em from
> www.rocelec.com (Rochester Electronics). They're most common in PLCC-44,
which
> you should be able to handle, even if, like me,
you didn't listen to Mom
when
she told you
to stop that.
It sounds like a nice chip. Since all I have is 3 1/2" 1.44mb drives I
will
have a fixed 500 Khz clock, thus less programing. Also the chips are
cheap
if you can find them $7.25 @ BG micro. I was looking some nec? chips at
Rochester
and they were over $75 each.
If you must use a WD part, which I prefer also, then
> use a WD179x with a FDC9229. That does everything in two chips, including
> selecting the appropriate clocks. The 2797 uses an analog PLL and, unless
> are satisfied with a single data rate, that means
multiple filters and
analog
muxes, etc.
Thanks for the info. While a 2 Mhz machine would have been the speed of
system in the 80's I might as well go to 4 Mhz since the FPGA will run
that fast.
As a side note a 2 Mhz machine is about the same speed as a PDP-8. 1.5us
for a jump.
2.5 us for memory access.
--
Ben Franchuk --- Pre-historic Cpu's --
www.jetnet.ab.ca/users/bfranchuk/index.html