8 Aug
2011
8 Aug
'11
9:22 a.m.
On 7 Aug 2011 at 19:57, Jeff Jonas wrote:
My pre-PC systems (mostly Z80 CP/M)
all support 4 floppies per the original specs.
But NOOOOOOOOOOOOOO, the PC's "cable twist" ruined that,
limiting things to 2 floppies and 2 hard drives per controller.
Not 'till SATA have we been able to un-do that mistake :-(
The 5150 and 5160 both supported 4 floppy drives with the original
controller--what do you think the DC37 on the bracket of the
controller board was for? As both machines shipped with full-height
5.25" drives, there wasn't room for 4 drives in the primary box, so
the added ones were external. I know of lots of 8-bit CP/M boxes
with the same arrangement.
The cable "twist" was a very clever (but not original) solution to a
thorny problem of how one controlled the spindle motors on two drives
when there is only one motor control line. The fact that one could
also set all floppies to the second drive select was a bonus.
I have Ultrastor controllers that use two unassigned lines in the
floppy cable to support a third drive on the cable. And a few DTC
controllers could be jumpered to allow for a 4-drive "flat" cable at
the expense of having all drive motors come on at the same time.
The "4drives" shareware was the first DOS
support I found
for the hard drive controller at alternate addresses & IRQ.
You've led a sheltered life. All of my disk products allowed for
configuration of port, IRQ and DMA channel.
Dual display? What programs support that?
The do exist, in the professional software market.
Do the boards have clear plastic for you to see the
cores?
That's such a treat: true non-volatile memory!
True non-volatile memory is punched cards--until the termites and
mice get to them.
TI is currently shipping its MSP430 uC in a version that uses FRAM
for memory. Since it's a von Neumann (unified address space),
provessor, you can execute code out of FRAM. There's also MRAM, but
I don't know if that's being incorporated into any uC designs.
As an undergrad, I never had the budget for a HP
calculator
nor access to a HP desktop like my high school's.
Somehow a TI-55 sufficed for me as an EE undergrad.
Looking back, I just can't see how. It's *SO LAME*.
As undergrads, many of us had access to a slide rule and the "rubber"
book.
--Chuck