On Sat, 6 Oct 2001 at 01:25:28 +0100 (BST), ard_at_p850ug1.demon.co.uk (Tony
Duell) said:
> > BTW, I also need some info on the Intel 8271 disk controller - I've got
two
>
> I would not do a new design using the 8271. The chip is fairly hard to
> find now, and there are machines that _need_ them (like the old Acorn
> Systems).
OK, then. One 8271, starting bid $100 - just kidding :-)
> In fact, I'd probably use one of the all-in-one PC floppy controller
> chips unless there was a very good reason not to. Add a crystal and
> perhaps some cable driver chips. That's all...
Is "I don't know any suppliers for PC FDCs" a good reason?
Farnell Electronics don't seem to sell them, nor do Maplins, Electrovalue,
ESR Electronics or any other supplier I know. Care to tell me where I can
get them?
> > of these little devils and Intel's datasheet makes absolutely no sense
at
> > all. I've also got a Western Digital WD1770-PH 00-02 that I might be
able to
> > use instead. First of all, which is the better controller? The 8271 or
the
> > 1770? Also, is it possible to overclock a 1770 or an 8271 like you can a
> > 1772?
>
> Oh, use the 1770. It does double density (MFM) for one thing (the 8271 is
> single-density only). It also require many fewer support circuits I
> think.
OK, then. The 1770 it is.
> The 1770 and 1772 are closely related (the difference being the step
> rates the chips can produce). I would guess that the 1770 can be
> overclocked, but I've never tried it.
I think I'll keep it running at the normal speed (8MHz). But the machine
will have a 16MHz oscillator and a divider, with a few jumper blocks for
clock speed selection (8 and 16MHz for the FDC, 1, 2 or 4MHz for the 6502
and support circuitry). I've got two Western Design Center W65SC02s (14MHz
6502s! Woohoo!) to play with, plus a Synertek SY6502A (the 2MHz one), two
W65SC22s (10MHz WDC 6502s) and two Synertek 6522s (1MHz).
So now I'm left with two questions:
1) Has anyone got any source code for the WD1770? 6502 ASM, C, anything.
2) Has anyone got a schematic for a fairly half-decent 16-colour (or
better) video card that can be modified to work on a 6502? I've had a look
at the NASCOM schematics but I've heard Bad Things(tm) about the NASCOM
video system. Aparrently Gemini and a few others produced colour video cards
for the NASCOM. Anyone got schematics for these? Graphics would also be nice
(the NASCOM video system is text only).
BTW, I'd like to avoid obsolete components if that's at all possible.
I've got a Hitachi HD6845 but if the 40-odd page datasheet is anything to go
by, it's a real dog to use... And it only works in monochrome. I have got a
MOS Tech 6568(?) VIC-II, the same one used in the UK Commodore 64. The PSU
for this C64 is fried, took out some of the support components with it.
TIA.
--
Phil.
philpem_at_bigfoot.com
http://www.philpem.f9.co.uk/
Received on Sat Oct 06 2001 - 15:51:33 BST