Seemingly odd hardware design decisions

[bluejay]

Macintosh - literally the only computer that uses RS422 serial.

[remz]

And speaking of serial ports: Who decided that it would be a brilliant idea to have both serial, external SCSI and parallel ports to use DB-25 with often random pin gender, fully aware that mistake connection might toast the machine and/or device?

[potatohead]

On 1/30/2021 at 9:11 PM, bluejay said:

That reminds me. Apple doesn't have a functioning backspace key either.

Well, it does move the cursor back one space.  What it doesn't do is delete.

[Keatah]

On 2/2/2021 at 9:10 AM, Casey said:

I'd offer up the Commodore 1541 disk drive as a whole.  The only reason it exists in the first place is that the 1540 was not compatible with the 64 because it was too fast.  By that time, Commodore already had the hardware bug fixed and could have made a fast disk drive for the 64 (like the 1571 was later to the 128).  But they chose to just make the 1540 even a bit slower so that it was compatible with the 64.  That was a dumb decision. 

As a kid I was always dumbfounded as to why it had to have its own CPU. And despite that it ran so much slower than Apple's Disk II.

 

The Disk II was cost-cutting in an elegant way. Not too many products are like that. It only cost $100 - $125 to make them. And they sold them initially at around $500. A cash cow 2BSHUR.

 

The drive is slick because the console's 6502 becomes part of the drive when you need to access it. It sets the stage for the timing and therefore nothing else takes place during read/write.

 

On 1/30/2021 at 11:11 PM, bluejay said:

That reminds me. Apple doesn't have a functioning backspace key either.

I have a patched firmware in the //e that allows for a real backspace/delete as we know it today. I seem to recall some WP software that did similar.

 

[Keatah]

10 hours ago, remz said:

The video composite RCA output on the Amiga 500 and Amiga 2000. It outputs monochrome.

I hated that and was surprised they'd do such a move on what was supposed to be a cutting-edge graphics computer.

 

On 2/4/2021 at 11:21 PM, Krebizfan said:

Subset products with additional incompatibilities to prevent cannibalization of the main product tend to be failures.

After getting duped (as kids) by the 5200 being an 8-bit computer in disguise we latched on to looking for things like that. From then on we looked to see if our purchases could properly be expanded and not pigeonholed into one product line. For a while this extended all the way down to cables and controllers.

 

On 2/4/2021 at 11:21 PM, Krebizfan said:

The 80186 was cheaper than the 8088 and incorporated what would otherwise require additional support chips. 

The 80186 was hugely popular in custom test instruments, controllers, and other industrial stuff. It failed in the consumer arena because it was not software compatible with the 8088/8086. Something to do with the memory layout IIRC. Anyways.. The consumer sphere thought it not a mainstream processor by any means. And by being semi-custom it didn't have enough design flexibility for consumer products.

 

Sometimes it's best to have things broken down into more granular modules & chips rather than all-in-one solutions.

[Krebizfan]

There were a smattering of systems with the 8018x with IIRC one disabling the added components on the chip and instead implementing full IBM PC compatibility. Sounds weird but saves a bit of money. Improved 80186/80188 derivatives had more success with the HP Hornet showing up in HP palmtops and the NEC V40 being the CPU for the Olivetti PC1. Strangely, the Handheld DOS machines which eschewed IBM PC compatibility were built with 80C88 and had a lot of discrete logic. 

 

Apple's Disk II was cheaper to make at the beginning but ultimately was counterproductive as some Macs had to include a modified 6502 to keep compatibility with the older formats. 

[Keatah]

Don't recall anyone ever hooking a DISK II to a MAC. Nor do I recall any MAC having a 6502 onboard for that purpose. MAC has been 3.5" from the start.

 

[Krebizfan]

19 minutes ago, Keatah said:

Don't recall anyone ever hooking a DISK II to a MAC. Nor do I recall any MAC having a 6502 onboard for that purpose. MAC has been 3.5" from the start.

 

The Mac used the IWM which allowed exchange with the Apple II's 3.5" floppies and had functionality derived from the Disk II design. That led to more complex layers of hardware to keep compatibility before reaching the expense of the I/O Processor which was a 6502 paired with 32K of RAM and some other features. Apple Tech Support: IOP Description (angelfire.com)

 

[youxia]

19 hours ago, remz said:

The video composite RCA output on the Amiga 500 and Amiga 2000. It outputs monochrome. What were they thinking, when even the 4-years older Commodore 64 had super sharp S-Video output.

The A520 rf modulator is an inergonomic abomination.

That is indeed bizarre, when considered now. But back then it wasn't such a big deal, at least to us kids. Everybody knew that you had to get a modulator, and its poor quality wasn't really standing out much since we lacked any sort of comparison material.

[bluejay]

Some macs did have a 5.25" floppy drive alright, but they were Lisa based twiggy drives, so I suppose it's irrelevant. Also, although having the same connector, Unidisks and Duodisks are not compatible with the Macintosh. I tried, didn't work.

[Keatah]

4 hours ago, Krebizfan said:

Apple's Disk II was cheaper to make at the beginning but ultimately was counterproductive as some Macs had to include a modified 6502 to keep compatibility with the older formats. 

What were those older formats?

 

[Krebizfan]

1 hour ago, Keatah said:

What were those older formats?

 

The GCR disk formats (400k and 800k) as implemented by the IWM or SWIM. In the case of the IIfx and Quadra 900 and 950 models, the SWIM was attached to the I/O Processor which includes a 6502. The SWIM cost more than the 82077A and the drives were also more expensive because of the need to have variable rotation rate. 

 

For Bluejay, Apple had several models of 3.5" drive that were supposed to connect to both Apple II and Mac: the Apple 3.5" External and the Superdrive external though in some cases it was necessary to add a newer controller card.  The Apple 3.5" Disk Controller Card includes a SWIM controller. 1.44 MB formats need the SWIM. 

[bluejay]

Then... I happen to have an 800k external floppy drive for my Macintosh. Can I hook this up to my Apple //e and expect it to work?

[Krebizfan]

36 minutes ago, bluejay said:

Then... I happen to have an 800k external floppy drive for my Macintosh. Can I hook this up to my Apple //e and expect it to work?

I would suggest asking this in the Apple II sub-forum and provide information on which specific model of drive and specific controller you have. There are pairings that work; pairings that don't work; and according to the FAQ, one pairing that is liable to damage both card and drive. 

[ClausB]

On 2/5/2021 at 9:39 PM, bluejay said:

Macintosh - literally the only computer that uses RS422 serial.

Literally not true. Many older industrial computers used it.

[ClausB]

On 1/30/2021 at 1:47 PM, youxia said:

ZX Spectrum's whole-word BASIC editor...

A hold-over from ZX80/81. It made the membrane keyboard tolerable.

[The Usotsuki]

1 hour ago, ClausB said:

Literally not true. Many older industrial computers used it.

Not to mention the Apple IIgs.

[DistantStar001]

On 1/30/2021 at 9:11 PM, bluejay said:

On 1/30/2021 at 8:57 PM, MHaensel said:

TRS-80 Model I, III, and IV: no backspace key.

That reminds me. Apple doesn't have a functioning backspace key either.

The back arrow acts as a backspace, or at least it does on my Model III.  Better than my Apple II's.  The key may say "Delete", but that's not what it does!

 

Also, What about Sinclair's decision to the same port for power as the cassette input/output?  

[MHaensel]

On 2/12/2021 at 4:22 PM, DistantStar001 said:

TRS-80 Model I, III, and IV: no backspace key.

 

On 2/12/2021 at 4:22 PM, DistantStar001 said:

The back arrow acts as a backspace, or at least it does on my Model III.

Today I learned! In BASIC, and possibly other programs, you're correct. Model I SCRIPSIT used CTRL-D as backspace. Another program (whose name escapes me) used F1.

Edited February 14, 2021 by MHaensel
Clarified backsapce key depends on program

[bluejay]

Commodore 8 bit computers (aside from maybe the C128) - Idiotic cursor keys. I suppose you could get used to it after a while but it is difficult to use for most people and is impractical in many ways. Surprised no one mentioned this yet.

 

Compaq Portable II - Why only 4 ISA slots, two of which are taken by the video and I/O card, leaving one 8 bit and one 16 bit slot? I suppose it was to reduce the size, but I think they've gone too far.

[Krebizfan]

19 minutes ago, bluejay said:

Compaq Portable II - Why only 4 ISA slots, two of which are taken by the video and I/O card, leaving one 8 bit and one 16 bit slot? I suppose it was to reduce the size, but I think they've gone too far.

For the Compaq portable, you should add the bonus memory expansion slot on the bottom of the motherboard. Compare it with the IBM Portable Personal computer which has several slots that need very short cards because of the drive placement and really can't be used at all or the disk drive cable would be rubbing against the card. 

 

Adding 4 slots would extend the system another 3.2" to just over 16" and, more importantly, would require beefing up the power supply. The full IBM AT had almost 200w power supply for its eight slots and drive bays but didn't have built in CRT. The Compaq Portable II power supply was only 130 watts.