25 Apr
2008
25 Apr
'08
4:34 a.m.
Date: Thu, 24 Apr 2008 22:25:49 -0500
From: Jim Leonard
Wow, I can't see it being useful at launch with
16K -- the DOS 1.0 took up
about 11K if memory serves, and command.com 5K all by itself... I guess
that left 1.5K to run BASIC.COM and that was all she wrote...
But with the 5150, the diskette drive (160K format) was optional.
All you really needed was a CGA card to get going. You had BASIC in
ROM and a cassette tape interface. The CGA card could be hooked to a
modulator and make pretty pictures on your TV. IIRC, that's one of
the configurations described in the IBM literature.
As another poster has mentioned, it really did seem like the target
was the Apple II and TI 99/4 type of market, rather than the higher-
end "office" machines like the Morrow or Eagle. I almost bought a
NEC APC after I first saw a 5150, thinking that I'd completely
misunderstood IBM's marketing objectives.
Those "pick your poison" expansion slots are what saved that box,
which succeeded, sometimes it seems, in spit of IBM's worst efforts.
Maybe someone remembers that the US 120v 60Hz models were availble
quite a bit before the 220v 50Hz models were--and IBM charged a
premium for the 220v models. I remember going to the local sales
office on Arques and trying to place an order for a dozen of the 220v
models. "Not available yet" was the answer. So, says I, "How about
buying some US models and running them at 120v 50Hz via a
transformer?" "That would void the warranty" was the response.
Apparently IBM also refused to support US systems sent overseas to
50Hz land. It was very strange.
We bought a bunch of US 5150s and shipped them anyway. They ran fine
on 50Hz.
Cheers,
Chuck
25 Apr
25 Apr
12:05 p.m.
Chuck Guzis wrote:
Apparently IBM also refused to support US systems sent
overseas to
50Hz land. It was very strange.
That wasn't the least bit uncommon then, and still isn't now. Most
companies won't support equipment used outside the region in which it
was sold. At the very least, they won't provide warranty service, but
often they won't provide ANY service.
A variety of excuses are given for this, but I think the real reason
generally is to protect the margins of the organization (internal or
external) that does the authorized import into those regions, even if
(as in your example) that organization isn't even in place yet.
Eric
5:39 p.m.
models. "Not available yet" was the answer.
So, says I, "How about
buying some US models and running them at 120v 50Hz via a
transformer?" "That would void the warranty" was the response.
I wonder if it's the 'transformer' or the '50Hz' that voided the
warranty.
I can't see how it matters where the 120V comes from -- whether it's from
the distriution transformer bring the mains down from a multi-kV feeder
or whether it's from a small trasnformer taking in 220V/240V from
European mains. DId the terms of the warranty specify this?
Did very early machines have AC fans? All the later ones certainly had
12V DC ones that would be independant of mains frequency, but an AC fan
would run slower on 50Hz and could cause the machine to overheat. Was it
really that marginal (Acutally, given it's the IBM PC [1], I could
beleive it was).
[1] When I got my first IBM PC-family machine (a 5160), I took it to bits
(what a suprise) and sat down with the TechRef. Every few minutes I'd
exclaim 'They did WHAT???' as I found aother it of misdesign...
-tony
6:20 p.m.
Tony Duell wrote:
[1] When I got my first IBM PC-family machine (a
5160), I took it to bits
(what a suprise) and sat down with the TechRef. Every few minutes I'd
exclaim 'They did WHAT???' as I found aother it of misdesign...
That's not the first time you've mentioned that, so now I have to ask
you: What's the #1 most glaring misdesign you can remember about the
5150 or 5160?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
6:43 p.m.
Jim Leonard wrote:
Tony Duell wrote:
I never studied the 5150 schematics, although I once designed an ISA
plug in card containing a 68020, DRAM, and three ASICs. We had no ISA
specs to design off of, so I just looked at the bus interface part of te
PC design.
Two things come to mind, one of which was recently mentioned. The
interrupt structure was poor -- using edge triggered interrupts prevents
sharing an interrupt line. As recall the choice of edge or level
sensitive interrupts is a matter of software (programming a control
register in the interrupt controller chip). There was no cost
associated with doing it one way or the other. Someone just decided
incorrectly, and once the convention was set, it couldn't be undone.
Another silly thing is that refresh was controlled by a DMA channel.
I'm sure it saved a couple chips, but it meant that errant, or
malicious, software could turn off the refresh and cause the memory
state to melt. A friend wrote a program that turned off that DMA
channel on purpose, but made sure his program would touch every row in
the DRAM frequently enough that his program would keep running.
However, if anyone tried to halt the program to capture the memory image
so they could reverse engineer his game, they'd get corrupted memory.
[1] When I got my first IBM PC-family machine (a
5160), I took it to
bits (what a suprise) and sat down with the TechRef. Every few minutes
I'd exclaim 'They did WHAT???' as I found aother it of misdesign...
That's not the first time you've mentioned that, so now I have to ask
you: What's the #1 most glaring misdesign you can remember about the
5150 or 5160?
6:56 p.m.
Jim Battle wrote:
Jim Leonard wrote:
> Tony Duell wrote:
>> [1] When I got my first IBM PC-family machine (a 5160), I took it to
>> bits (what a suprise) and sat down with the TechRef. Every few
>> minutes I'd exclaim 'They did WHAT???' as I found aother it of
>> misdesign...
>
> That's not the first time you've mentioned that, so now I have to ask
> you: What's the #1 most glaring misdesign you can remember about the
> 5150 or 5160?
Duh, the other really stupid one: taking the 1MB memory space and
putting BIOS and video where they did.
11:13 a.m.
Alexandre Souza wrote:
True the BIOS being located at the top was not the problem, but putting
video at 0xA000. Sure, I realize that IBM didn't expect the PC to have
the life it did, but considering this: the TRS-80 family and many other
8 bitters had already evolved to architectures where the memory space
was fully RAM populated and hardware was mapped in and out as needed.
Moore's law was at the time a well known trend, and it wouldn't take a
genius to calculate that the 16-fold increase in memory would be outrun
in just a few years.
Duh, the other
really stupid one: taking the 1MB memory space and
putting BIOS and video where they did.
Was that a misdesign? If I'm not mistaken this is a particularity of
the 8086/8088, they expect the BIOS to be in FFxxsomething :o\
2:01 p.m.
Jim wrote:
I realize that IBM didn't expect the PC to have
the life it did,
[...]
Moore's law was at the time a well known trend,
and it wouldn't take a
genius to calculate that the 16-fold increase in memory would be outrun
in just a few years.
Reed your first statement I quoted above again.
Anyhow, even if they had put the video at 0xE0000, Moore's law *still*
would have resulted in the machine running out of address space, and
that wouldn't have been delayed by even a year, so whether they ignored
Moore's law in picking the address of the video card is completely
irrelevant.
And although it wasn't obvious from the original tech ref and BIOS
listing, they probably expected there to be other memory-mapped
devices above 0xA0000, and firmware extensions.
Even though we (the users and programmers) didn't like the video
being at 0xA0000 by the mid-1980s, I don't think it can really be
considered a huge mistake. They left room for more than half a
megabyte of RAM. I'm not aware of any other mainstream microcomputer
introduced in or before 1981 that could support contiguous, directly
adressable RAM configurations from 16KB to over 512KB.
[Geez, I can't believe I'm defending the engineers that developed
the PC. Now I feel like I need to take a shower.]
4:08 p.m.
Duh, the other really stupid one: taking the 1MB
memory space and
putting BIOS and video where they did.
Well, they had to put some ROM at the top of the address space because an
8088 starts executing at FFFF:0000 after a reset.
That IMHO is another Intel Misfeature, which goes as follows :
The 8080 (and for that matter the Z80) starts esecuting at location 0 on
a reset.
Therefore, the origianl Intellec 8080 development system, with a
lights-and-switches panel had _RAM_ at location 0. You wrote a jump
instruciton at locaition 0 pointing to your code (or the monitor ROM),
then reset the processor and gave it the bus. It executed the jump, and
thus the desired progam
Therefore CP/M was designed to have RAM at location 0, since it was
origianlly developed on Intel development machines
On later CP/M machines, without a front panel, it was necessary to RAM at
location 0, and thuse a little ROM/logic that provided the power-on jump
to a ROM at the top of the address space after a reset.
So far, so good.
The Intel mesifeature was making the 8088 and 8086 start at a location
near the top of the memory map after a reset as as attempt to get round
this 'problem' not realising that _any_ fixed reset location would have
essentially the same effect.
And to make the 80286 (and later) processors start at the same location
as the 8085, and thus somewhere in the middle of their much larger
address space was plain insane.
-tony
4:53 p.m.
Tony Duell wrote:
The Intel mesifeature was making the 8088 and 8086
start at a location
near the top of the memory map after a reset as as attempt to get round
this 'problem' not realising that _any_ fixed reset location would have
essentially the same effect.
And to make the 80286 (and later) processors start at the same location
as the 8085, and thus somewhere in the middle of their much larger
address space was plain insane.
And yet people continue to buy this garbage. Why, I'll never understand.
-Dave
--
Dave McGuire
Cape Coral, FL
27 Apr
27 Apr
12:16 a.m.
Dave McGuire wrote:
One word: Software.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
And to make
the 80286 (and later) processors start at the same
location as the 8085, and thus somewhere in the middle of their much
larger address space was plain insane.
And yet people continue to buy this garbage. Why, I'll never understand.
25 Apr
25 Apr
11:25 p.m.
Jim Battle wrote:
When I read the above, I read it as "I didn't like the design of the
5150 so I created my own computer to stick in an ISA slot" :-)
That's not
the first time you've mentioned that, so now I have to ask
you: What's the #1 most glaring misdesign you can remember about the
5150 or 5160?
I never studied the 5150 schematics, although I once designed an ISA
plug in card containing a 68020, DRAM, and three ASICs. We had no ISA
specs to design off of, so I just looked at the bus interface part of te
PC design. Two things come to mind, one of which was recently
mentioned. The
interrupt structure was poor -- using edge triggered interrupts prevents
sharing an interrupt line. As recall the choice of edge or level
sensitive interrupts is a matter of software (programming a control
register in the interrupt controller chip). There was no cost
associated with doing it one way or the other. Someone just decided
incorrectly, and once the convention was set, it couldn't be undone.
What could have been a reason *for* using edge-triggered interrupts?
A friend wrote a program that turned off that DMA
channel on purpose,
but made sure his program would touch every row in the DRAM frequently
enough that his program would keep running. However, if anyone tried to
halt the program to capture the memory image so they could reverse
engineer his game, they'd get corrupted memory.
That's dedication! I wrote a memory-copy routine that used DMA but I
could never get it reliable (when refresh is off you only have so much
time and rarely were you copying something that touched every row, so
the copy would work and then the *rest* of the DRAM was gone).
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
26 Apr
26 Apr
3:58 p.m.
Two things come to mind, one of which was recently
mentioned. The
interrupt structure was poor -- using edge triggered interrupts prevents
sharing an interrupt line. As recall the choice of edge or level
sensitive interrupts is a matter of software (programming a control
register in the interrupt controller chip). There was no cost
associated with doing it one way or the other. Someone just decided
incorrectly, and once the convention was set, it couldn't be undone.
I thought it saved a tivial amount of TTL logic to use edge-triggered
active high interrupts in the realtime clock/heatbeat circuit -- linking
the 8253 output to the 8259. But it was a tirvial amount of logic in a
machine of that complexity/price...
[Why, Oh why, do people always assume the cheapest solution is the best
and will sell the most units. In my workshop that is _never_ the case]
Another silly thing is that refresh was controlled by a DMA channel.
I'm sure it saved a couple chips, but it meant that errant, or
And, indeed, using the 8237 DMA chip with a paging register (and not even
doing that as elegantly as the FTS-88 did, which at least had one paging
register per DMA channel) rather than using the 8089 'I/O processor'.
-tony
3:55 p.m.
That's not the first time you've mentioned
that, so now I have to ask
you: What's the #1 most glaring misdesign you can remember about the
5150 or 5160?
Oh, that's easy. The edge-triggered active high interrupts.
And on the software side, the fact that the BIOS serial port routines
don't use interrupts, making it necessary ot hit the hardware directly if
you wanted any decent data rate without dropping characters. You know, I
was under the impression that the whole point of device driver routines
was so you could make different physical hardware look the same to the
applicaiton programs.
-tony
5:02 p.m.
Y'all need to re-read my post a couple of days ago. BIOS was there
mainly for ROM/Cassette BASIC (the *only* PC to do that). The
original choice for OS was CPM, but that story has been well told.
Although I wonder how many people realize the inside joke of one of
the BASIC demo programs? And who says IBM doesn't have a sense of
humor?
On Apr 26, 2008, at 12:55 PM, Tony Duell wrote:
That's not
the first time you've mentioned that, so now I have to ask
you: What's the #1 most glaring misdesign you can remember about the
5150 or 5160?
Oh, that's easy. The edge-triggered active high interrupts.
And on the software side, the fact that the BIOS serial port routines
don't use interrupts, making it necessary ot hit the hardware
directly if
you wanted any decent data rate without dropping characters. You
know, I
was under the impression that the whole point of device driver
routines
was so you could make different physical hardware look the same to the
applicaiton programs.
-tony
27 Apr
27 Apr
1:05 p.m.
Y'all need to re-read my post a couple of days ago. BIOS was there
mainly for ROM/Cassette BASIC (the *only* PC to do that). The
Was it? (or more correcrtly 'were they?' since the PC/XT, PC/AT,
PortablePC and PCjr also had ROM BASIC). I thought at least one clone had
an illegal copy of Microsoft BAISC (until Microsoft found out about it)
and at least one clone had a legal ROM BASIC.
original choice for OS was CPM, but that story has
been well told.
What has that got to do with a buggy/incomplete RIOS? Can't a CP/M CBIOS
be written to use ROM routines rahter than talk to the hardware directly?
Although I wonder how many people realize the inside joke of one of
the BASIC demo programs? And who says IBM doesn't have a sense of
humor?
OK, I'll bite. I don't know the BASIC demos at all. What's the demo, and
what's the in-joke?
-tony
2:08 p.m.
On Apr 27, 2008, at 10:05 AM, Tony Duell wrote:
OK, I was trying to figure out the "right" way to say it. Only IBM
produced PCs have ROM BASIC. None of the other clones did (at least I
don't recall).
There were a number of BASIC demo programs (mainly for the CGA). One
of them was an animated elephant tap dancing to "music" coming out of
the PC's speaker.
When the IBM "suits" showed up to negotiate for C/PM, they were told
"politely" that IBM would only produce a PC when elephants learned to
tap dance and to not waste their time.
I believe the demo was shown during the announcement of the PC (ie
running in the background). I think you see the joke now. :-)
TTFN - Guy
Y'all need to re-read my post a couple of days ago. BIOS was there
mainly for ROM/Cassette BASIC (the *only* PC to do that). The
Was it? (or more correcrtly 'were they?' since the PC/XT, PC/AT,
PortablePC and PCjr also had ROM BASIC). I thought at least one
clone had
an illegal copy of Microsoft BAISC (until Microsoft found out about
it)
and at least one clone had a legal ROM BASIC. original choice for OS was CPM, but that story
has been well told.
What has that got to do with a buggy/incomplete RIOS? Can't a CP/M
CBIOS
be written to use ROM routines rahter than talk to the hardware
directly?
Although I wonder how many people realize the inside joke of one of
the BASIC demo programs? And who says IBM doesn't have a sense of
humor?
OK, I'll bite. I don't know the BASIC demos at all. What's the demo,
and
what's the in-joke? 
2:16 p.m.
On Sunday 27 April 2008 13:05, Tony Duell wrote:
No reason why not that I can see. For that matter, why not shove most of
CP/M into ROM? I think I might just do that one of these days, except
replacing some of the standard stuff with improved versions, like SD for
DIR, etc.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
original
choice for OS was CPM, but that story has been well told.
What has that got to do with a buggy/incomplete RIOS? Can't a CP/M CBIOS
be written to use ROM routines rahter than talk to the hardware directly?
3:06 p.m.
Roy wrote:
For that matter, why not shove most of CP/M into ROM?
You've just reinvented the Intel 80150 "Operating System Processor".
The Intel 80130 and 80150 contain 16KB of masked ROM, three timers, and
an interrupt controller. The 80130 ROM contains the iRMX-86 kernel;
the 80150 ROM contains CP/M-86.
Eric
4:15 p.m.
On Sunday 27 April 2008 15:06, Eric Smith wrote:
Roy wrote:
Yeah, well, I never did get much into the -86 version anyhow, never liked
that CPU all that much. I can wrap my head around the Z80 and similar parts
a whole *lot* easier. :-)
And masked ROM? Not for me, that's for some manufacturer who can afford to
amortize the setup costs never mind the lack of re-usability in those parts.
I'll stick to EPROMs or similar, thanks anyway...
Now there are all these empty EPROM sockets on my BBII, and I can stick up to
4K in each on, that should do it, I guess.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
For that matter, why not shove most of CP/M into
ROM?
You've just reinvented the Intel 80150 "Operating System Processor".
The Intel 80130 and 80150 contain 16KB of masked ROM, three timers, and
an interrupt controller. The 80130 ROM contains the iRMX-86 kernel;
the 80150 ROM contains CP/M-86.
26 Apr
26 Apr
5:47 p.m.
On Saturday 26 April 2008 15:55, Tony Duell wrote:
I've not programmed to the level of actually getting paid to do so, but it's
been a casual interest of mine for a long time. For my CP/M boxes I was okay
with assembler, but the 8088 stuff was so distasteful to even look at I
decided to learn c. So I spent a *lot* of time hanging out in the fidonet
C_ECHO. To the point where the actually asked me to be moderator, a couple
of different times, which I declined both times. :-)
Anyhow, in those days *everybody* considered the BIOS code to be really and
truly awful stuff, and it was pretty much common practice to bypass them
every chance you got. There was some standardization for some things,
like "fossil" and such for serial comms, for one example.
I always thought it was an absurd waste of both time and space in terms of
coding to have to do stuff like figure out which kind of monitor you had
hooked up to the machine and code things differently in each case. But
that's my byte-stinginess from the CP/M days showing through, I guess.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
That's not
the first time you've mentioned that, so now I have to ask
you: What's the #1 most glaring misdesign you can remember about the
5150 or 5160?
Oh, that's easy. The edge-triggered active high interrupts.
And on the software side, the fact that the BIOS serial port routines
don't use interrupts, making it necessary ot hit the hardware directly if
you wanted any decent data rate without dropping characters. You know, I
was under the impression that the whole point of device driver routines
was so you could make different physical hardware look the same to the
applicaiton programs.
5928
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22 comments
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alexandre-listas＠e-secure.com.br -
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
cisin＠xenosoft.com -
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ggs＠shiresoft.com -
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rtellason＠verizon.net -
trixter＠oldskool.org