Intel strikes back with a parallel x86 design

[keith]

There was, however, MDA (no graphics, text only). Most of the
first-generation PCs I saw had those, rather than CGA, and my impression was
that they were a concurrent part of the original release.

The monochrome display/adapter wasn't at issue. Both the monochrome and
color-graphics adapters and the associated displays were indeed announced
and shipped with the first 5150s. As I've said many times, I have a
"first day order" 5150 with both adapters and an original monochrome
monitor (bought the color display with the PCjr ;-).

 

[keith]

Heh, I forgot about those funny side-car expansions that screwed
into the side of the Jr, each one extending the width of the box
by at least an inch.

..9", IIRC. I only put the meoory sidecar on the kid's. I also had a PC1
for any "computing".

And then there was that terrible "chicklet" keyboard (ala TRS-80 Coco I),
which has keys resembling the look-and-feel of a touchtone phone.

THe chicklet keyboards were only on the original Jrs. Later ones had a
real keyboard, no IR.

With the standard memory configuration, performance was often sluggish
due to shared RAM for video and CPU. Expanding memory helped that.
I'm not sure that dual-cartridge port was a great idea either (imagine
Nintendo-style cartridges being plugged into the front of your PC).

I don't see hat was wrong with that. It was more memory (ROM). There
wasn't much usefull software one the artridges though.

It didn't even come with a parallel port, you had to add a side-car just
for that (and I think the limit was three side-cars). Lack of DMA for
disk transfers was a real lame feature.

I'd forgotten about the printer port. I know a loto of people who kludged
up a DMA controller to attach hard disks(of all things). That said, I
always thought DMA for floppy disks was overkill. The original PC used a
DMA channel for DRAM refresh. I don't remember what the Jr. used.

Perhaps the biggest problem was that it wasn't 100% IBM PC backwards
compatible. I seem to remember it had a different floppy controller
so that PC software using direct hardware access to the floppy (e.g.,
COPYII-PC) wouldn't work on the Jr. Some of the I/O ports were also
at different addresses, and the memory map wasn't quite the same as
the PC. So the Jr. required special versions of many programs.

Yep! It was a weird duck. They didn't want people to use it as a PC!

But some things were nice about the machine-- such as having decent
16-color graphics (as opposed to that ugly PC CGA), 3-voice sound chip
(IIRC), etc.

For the price I paid it served well (got the kid off mine .

---

Another vote for worst would have to be the TRS-80 MC-10 Color
Computer-- a stripped down CoCo about the size of a Timex Sinclair,
also with a (very small) chicklet keyboard.

I didn't like any of the RadioShaft computers other than the original
TRS80.

 

[Jason Lee Eckhardt]

.9", IIRC. I only put the meoory sidecar on the kid's. I also had a PC1
for any "computing".


THe chicklet keyboards were only on the original Jrs. Later ones had a
real keyboard, no IR.

Apparently, I had the original. I believe it was December 1984
when I unpacked it.

I don't see hat was wrong with that. It was more memory (ROM). There
wasn't much usefull software one the artridges though.

It wasn't so much the idea of cartridges, but that those two slots consumed
a large part of the real estate that could have been used for, say,
a second floppy or other expansion space. To add a second floppy,
one had to buy a giant "thing" to sit on top of the original chassis.
It had the same dimensions (length/width) as the junior, though
not quite as thick. The Jr started approaching the size of a small
microwave oven with that attachment...

I'd forgotten about the printer port. I know a loto of people who kludged
up a DMA controller to attach hard disks(of all things). That said, I
always thought DMA for floppy disks was overkill.

It certainly makes for a more pleasant and efficient computing
experience to have DMA for disk. For example, on the Jr, you
couldn't type while the disk was operating. Likewise, simultaneous
disk access and serial port (modem) usage was a problem.

The original PC used a
DMA channel for DRAM refresh. I don't remember what the Jr. used.

IIRC, the Jr had no DMA controller at all. It did have an 8253 PIT,
though. I don't recall if it used that for refresh.

Yep! It was a weird duck. They didn't want people to use it as a PC!
<guffaw>

I guess as long as software only used the BIOS routines, and avoided
hardware programming, things would run. But, the BIOS routines
were so hideously slow, that alot of software avoided them.
For some programs, like COPYII-PC, direct hardware access was the
only way to get the job done at all.

On the other hand, the game software for Jr often used its
advanced graphics and sound capabilities so that its versions
were much better than the PC versions (e.g., King's Quest I).

For the price I paid it served well (got the kid off mine .

It was a step up from my Z80-based Model I at the time, but still
weird (my programmer friends had "real" PCs). It did get plenty
of mileage, though.

I didn't like any of the RadioShaft computers other than the original
TRS80.

I liked the Model I, and the PC-2 (a handheld with a bitmapped
display-- it was the only PC-* one you could find hardware info for, to
program it in something other than BASIC).

 

[keith]

Apparently, I had the original. I believe it was December 1984
when I unpacked it.

There was a recall on the original IR "chicket" keyboard to replace them
with a real keyboard (not a Model-M, but not so bad either). Perhaps you
missed it?

It wasn't so much the idea of cartridges, but that those two slots consumed
a large part of the real estate that could have been used for, say,
a second floppy or other expansion space.

The idea behind the Jr. (as silly as such a thing could be) was that it
was a *home* computer, rather than a (cheaper) "personal" business
computer. "Game" cartridges were a big thing (that didn't transfer well
to the PC). Maybe there is something to be learned here?

To add a second floppy,
one had to buy a giant "thing" to sit on top of the original chassis.
It had the same dimensions (length/width) as the junior, though not
quite as thick. The Jr started approaching the size of a small
microwave oven with that attachment...

Come on! It was still smaller than a PC. If one wanted a PC, well...

It certainly makes for a more pleasant and efficient computing
experience to have DMA for disk. For example, on the Jr, you couldn't
type while the disk was operating. Likewise, simultaneous disk access
and serial port (modem) usage was a problem.

SMOP! Hard disks didn't grow (reliable, anyway) DMA until '90 or so. Why
was a simple floppy so bad, when hard disks worked well. Even Apple had
PIO floppys, forever.

IIRC, the Jr had no DMA controller at all. It did have an 8253 PIT,
though. I don't recall if it used that for refresh.

What did the memoy refresh? ...just asking, I don't remember.

I guess as long as software only used the BIOS routines, and avoided
hardware programming, things would run. But, the BIOS routines were
so hideously slow, that alot of software avoided them.

Come on! At 4.77MHz, BIOS ROM wasn't any slower than DRAM, (which also
had the refresh penalty). Remember, it was an 8-bit bus, with memory on
the ISA bus.

For some
programs, like COPYII-PC, direct hardware access was the only way to
get the job done at all.

I don't buy it. CopyII-PC was superrior because it buffered everythinr to
RAM as much as it could, not because it was diddling with the hardware.

On the other hand, the game software for Jr often used its advanced
graphics and sound capabilities so that its versions were much better
than the PC versions (e.g., King's Quest I).

Most of the games worked quite well.

It was a step up from my Z80-based Model I at the time, but still
weird (my programmer friends had "real" PCs). It did get plenty of
mileage, though.

I got my "first-day-order" PC1 in April '81. My 3yo son had a blast with
it. I bought the Jr. later to get him off the thing. ;-)

I liked the Model I, and the PC-2 (a handheld with a bitmapped
display-- it was the only PC-* one you could find hardware info for,
to program it in something other than BASIC).

The IBM PC had all hardware documented, even BIOS (which Compaq made a
rather nice business out of).

 

[dgay]

Come on! At 4.77MHz, BIOS ROM wasn't any slower than DRAM, (which also
had the refresh penalty). Remember, it was an 8-bit bus, with memory on
the ISA bus.

The problem with the BIOS was bad code (IIRC, at least the display routines
and serial code were best avoided), not slow ROM access...

 

[Jason Lee Eckhardt]

The idea behind the Jr. (as silly as such a thing could be) was that it
was a *home* computer, rather than a (cheaper) "personal" business
computer. "Game" cartridges were a big thing (that didn't transfer well
to the PC). Maybe there is something to be learned here?

I'm not sure what is to be learned, other than the space for two
cartridge slots can probably be put to better use

What did the memoy refresh? ...just asking, I don't remember.

I suspect it was the 8253 PIT (programmable interval timer) I mentioned,
though I cannot say for certain without digging out the PC Jr Tech Ref
manual. Of course, a small bit of extra circuitry would be
necessary in order to generate the dummy read cycles (whereas the
original PC used a combination of one 8237 DMA channel and one
8253 timer channel).

Come on! At 4.77MHz, BIOS ROM wasn't any slower than DRAM, (which also
had the refresh penalty). Remember, it was an 8-bit bus, with memory on
the ISA bus.

Actually, I wasn't referring to memory/bus speeds, but the speed of the
BIOS ROUTINES. For example, the BIOS routines for putting characters on
the screen were so inefficient that most software directly wrote to video
memory, bypassing the BIOS altogether (except to change video modes).
Likewise for putting pixels. Read the BIOS listings for INT 10h in the
PC Tech Ref Manual to see these examples.

I don't buy it. CopyII-PC was superrior because it buffered everythinr to
RAM as much as it could, not because it was diddling with the hardware.

Buffering has nothing to do with COPYII's ability to get its job
done (i.e., duplicating odd disk formats).
COPYII had to program the hardware directly in order to work around
BIOS limitations (this is why the Jr. had its own special version).
That is, the BIOS routines had no provision for reading disks with certain
storage anomalies. In other words, the BIOS only presents a limited
programmer interface for reading sectors from the disk. Direct FDC
programming is necessary to read odd disk arrangements as presented by
certain copy-protection schemes (bad sector IDs, using gaps for data,
bad AMs, etc).

The IBM PC had all hardware documented, even BIOS (which Compaq made a
rather nice business out of).

Yes, I love the old IBM Tech Ref Manuals. Too bad all hardware
wasn't so well-documented.

 

[prep]

More revisionist history.

That `revision' happened in... 1980?, and the statment was made by the Apple
employee who was dropping off the loan-for-evaluation Lisa.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

 

[MSCHAEF.COM]

There was, however, MDA (no graphics, text only). Most of the
first-generation PCs I saw had those, rather than CGA, and my impression was
that they were a concurrent part of the original release.

My understanding is that IBM's original offerings were these:

CGA
- 80x25 and 40x25 text with an 8x8 character cell and color attributes
- 640x200 Monochrome Graphics
- 320x200 4-color Graphics Black + (White/Cyan/Magenta or Red/Yellow/Green)

MDA
- 80x25 text with a 14x9 character cell

These adapters had different base addresses and could be run
on the same machine.

The Hercules board was intended to be a way to add graphics to MDA-only
PC's. It connected to the IBM monochrome display and added a 720x350
(approx) graphics mode to the modes supported by the MDA. The Hercules
Plus board added loadable fonts and used some of the attribute bits to
allow selection between signifantly more characters. IIRC, MS Word for DOS
used this to get a little closer to WYSIWYG, without the overhead of full
fledged graphics.

Compaq's compatible PC's, the Portable and the Deskpro, had a custom video
board and monitor that could do either CGA graphics or MDA-style text with
a 14x9 character cell. What it didn't do is emulate the Hercules graphics
mode (too bad, too.)

-Mike

 

[George Macdonald]

That `revision' happened in... 1980?, and the statment was made by the Apple
employee who was dropping off the loan-for-evaluation Lisa.

No need for ?-marks. Go read it http://en.wikipedia.org/wiki/Apple_Lisa -
the Lisa went on sale as a business machine with 1MB memory; the Mac went
on sale a year later targeted at the consumer market.

 

[Terje Mathisen]

The problem with the BIOS was bad code (IIRC, at least the display routines
and serial code were best avoided), not slow ROM access...

You're right:

Serial code did not really exist at all in the BIOS (i.e. polled only!),
whereas the display bios actually did work, but the performance was
really bad if you wanted to do anything that required scrolling, or any
other kind of in-frame-buffer movement:

My own terminal emulator code became much faster after I wrote a full
replacement that did everything in a set of linked list memory buffers,
only copying the actual result to the frame buffer when idle.

Terje

 

[Jason Lee Eckhardt]

I suspect it was the 8253 PIT (programmable interval timer) I mentioned,
though I cannot say for certain without digging out the PC Jr Tech Ref
manual. Of course, a small bit of extra circuitry would be
necessary in order to generate the dummy read cycles (whereas the
original PC used a combination of one 8237 DMA channel and one
8253 timer channel).

After digging out the Jr Tech Ref, it appears that the 8253 was
not used for refresh. Instead, an interesting combination of the
6845 CRT controller and a custom gate array did the job. The sync
signals from the 6845 feed the gate array, which itself drives the
RAS and CAS of the RAMs. The gate array is also part of the video
graphics subsystem (providing the enhanced graphics modes, RAMDAC,
etc).

 

[keith]

After digging out the Jr Tech Ref, it appears that the 8253 was
not used for refresh. Instead, an interesting combination of the
6845 CRT controller and a custom gate array did the job. The sync
signals from the 6845 feed the gate array, which itself drives the
RAS and CAS of the RAMs. The gate array is also part of the video
graphics subsystem (providing the enhanced graphics modes, RAMDAC,
etc).

Now that you mention this, I do remember that the display controller did
the refresh. Anything that does a sequential access to memory will
refresh memory as a side effect. Thanks.

 

[Nate Edel]

I didn't like any of the RadioShaft computers other than the original
TRS80.

I loved the Model 100 and 102 portables...

 

[Grant Schoep]

(e-mail address removed) (MSCHAEF.COM) wrote in

My understanding is that IBM's original offerings were these:

CGA
- 80x25 and 40x25 text with an 8x8 character cell and color attributes
- 640x200 Monochrome Graphics
- 320x200 4-color Graphics Black + (White/Cyan/Magenta or
Red/Yellow/Green)

MDA
- 80x25 text with a 14x9 character cell

These adapters had different base addresses and could be run
on the same machine.

I'm not sure when it came along. But I remeber(wasn't that old at the
time... maybe about) we had this Tandy 1000, which had "Tandy 16 color" I
just remeber I thought it ruled because the graphics on it was better than
a lot of others kids Dad's computers. I think that was later though,
because it wasn't for a few years until we bought a real computer game for
it. Anyone know what time frame in here that Tandy 16 came out?

I remeber sitting at the dos prompt, trying to figure out how to play the
game "driver.exe" I could see that file listed on the dos 3.2 floppy, and
really wanted to figure out how to play it... :>

 

[Bill Davidsen]

(e-mail address removed) (MSCHAEF.COM) wrote in




I'm not sure when it came along. But I remeber(wasn't that old at the
time... maybe about) we had this Tandy 1000, which had "Tandy 16 color" I
just remeber I thought it ruled because the graphics on it was better than
a lot of others kids Dad's computers. I think that was later though,
because it wasn't for a few years until we bought a real computer game for
it. Anyone know what time frame in here that Tandy 16 came out?

I remeber sitting at the dos prompt, trying to figure out how to play the
game "driver.exe" I could see that file listed on the dos 3.2 floppy, and
really wanted to figure out how to play it... :>

I think the timeframe was mid to late 80's, after the XT came out. From
memory, it had an 80186 CPU (or 80188) which could be led to some
performance enhancements if you used assembler. It also supported 768k
(six) instead of 640k due to the controllers being in a better place.

 

[keith]

I think the timeframe was mid to late 80's, after the XT came out. From
memory, it had an 80186 CPU (or 80188) which could be led to some
performance enhancements if you used assembler. It also supported 768k
(six) instead of 640k due to the controllers being in a better place.

The 80186/8 weren't fully PC compatable. The IBM PC devlopers, in their
infinite wisdom, squated on "reserved" interrupts that were reserved for
the 80186/8, relegating the thing to the embedded market. ...too bad, it
was a nice processor. Some tried to make it compatable, but there were
always problems with anything that wrote to the hardware, which was
more than "common".

 

[Bill Davidsen]

The 80186/8 weren't fully PC compatable. The IBM PC devlopers, in their
infinite wisdom, squated on "reserved" interrupts that were reserved for
the 80186/8, relegating the thing to the embedded market. ...too bad, it
was a nice processor. Some tried to make it compatable, but there were
always problems with anything that wrote to the hardware, which was
more than "common".

Good point, although the Tandy 1000 did run most PC software. It run a
Tandy version of MS-DOS, which let you run 768k of memory. I never tried
to run anything else on the system, other things came along.

The 80186 was nice in many way for embedded, just as you noted. IIRC
there was an interrupt controller and some 1 bit parallel port which
could be taught to do RS-232 just by a driver to the correct voltage.

Speaking of which, wasn't the 8086 5 and 12v and the 8018[68] single 5v?
The memory is going...

 

[keith]

Good point, although the Tandy 1000 did run most PC software. It run a
Tandy version of MS-DOS, which let you run 768k of memory. I never tried
to run anything else on the system, other things came along.

Right, as long as every access to hardware went through a *DOS* interrupt,
the Tandy DOS worked. If it went to BIOS or diddled with bits directly,
not so good. That's clear by your 768K number, though a *compatable*
could have 704K with no problems (until much later when the EGA came out).

The 80186 was nice in many way for embedded, just as you noted. IIRC
there was an interrupt controller and some 1 bit parallel port which
could be taught to do RS-232 just by a driver to the correct voltage.

I don't remember any one-bit parallel ports, but it did have
integrated address decode logic (another issue in the DOS map), that I
suppose could be used for such. It also had integrated DMA and timers,
along with a few instruction improvements (stack sorts of thigns IIRC).

Speaking of which, wasn't the 8086 5 and 12v and the 8018[68] single 5v?
The memory is going...

Sheesh! ;-) Interesting note though, the 80186 and 80188 were origianlly
the same die, with only a bondout option difference. I think that was the
first time that was done.