Was there ever a serial based removable storage device?

[XOIIO]

Something which randomly popped into my head, although unlikely, and probably not that useful to the non tech savvy, I was wondering if there was ever a removable storage device with a serial connection, yes, usb is technically serial, but I mean a chunky db9 connector you'd hook into the back of your computer and get a bit of portable storage with, basically just a massively old version of a flash drive.

You'd need to use some command line interface to move files, if it could even store anything aside from text, or maybe some sort of special software, but it would really be cool if there was something like this for a brief period, or even to make something today that would give a bit of storage space. It wouldn't be for practicality of course.

I'm sort of envisioning a somewhat clunky thing made of cast metal with a couple diffused led's to indicate power and data transmission, and a db9 connector with proper screws to secure it in place for complete overkill, although I don't even know if a computer serial interface would be able to provide the power needed for such a device.

Thinking about it some more though, I remember getting a 256mb flash drive and how it was incredible compared to lugging around batch files on floppy disks, man was that the life, getting that much storage for this sort of device would be pretty clunky, I'm thinking a few megabytes might be more realistic if it was something made back in the day.

[Mr.B]

...or even to make something today that would give a bit of storage space.

MAX232 chip, PIC or AVR, Micro SD Card.
A bit of code for UART to SPI...
Done.

...although I don't even know if a computer serial interface would be able to provide the power needed for such a device.

Some specialised PCs such as Point of Sale computers support output of 12v or 9v or 5v on pin 9 of the DB9.
However I don't think I have ever seen this feature on a standard desktop PC.

[XOIIO]

...or even to make something today that would give a bit of storage space.

MAX232 chip, PIC or AVR, Micro SD Card.
A bit of code for UART to SPI...
Done.

...although I don't even know if a computer serial interface would be able to provide the power needed for such a device.

Some specialised PCs such as Point of Sale computers support output of 12v or 9v or 5v on pin 9 of the DB9.
However I don't think I have ever seen this feature on a standard desktop PC.

Yeah, ideally it would be using older tech, probably all through hole, or very very early surface mount style stuff, to give it sort of an 80's computing feel, if you were to make it yourself, even a hand drawn pcb just for that extra bit of old school feel to it.

Shame that the power feature isn't a common thing, I guess maybe that's why I couldn't find anything like this, it just wasn't really feasible with most serial ports, or it would need external power of some sort, but then you deal with old battery technology not lasting very long, and likely being quite bulky.

[T3sl4co1l]

Well, in those days, serial came in DB-25.

It wouldn't have been very hard to make an EMS (expanded memory) card that communicates via parallel port, but I have no freaking clue if that existed.  I see there was an ISA card with parallel port onboard... but that's side by side, not one-into-the-other...

I can take a guess that serial would've been all but useless.  EMS' purpose is a memory address window accessible by the CPU; the 8086 had no means to interrupt ranges of memory access (it doesn't have a memory mapper/controller, and anyway, spending hundreds of clock cycles on interrupt services for each byte or word of access would be excruciatingly wasteful!).  It wouldn't be so bad if the window is placed in system RAM (cache, really), but still, copying blocks of 64kB at a time, through a serial port, might not work very well at max. 115.2kbps.   (5.7 seconds per frame. If you're ripping through data, say, doing a database search, that's not very helpful...)

The ratio of speeds is just as gross today (fractional to several Gbps, depending on port and device speed, versus >100G at the CPU), but the amount of data transferred is fairly useful (megs), so we don't mind except when it's big video files or CDs or whatnot.

Tim

[edavid]

Something which randomly popped into my head, although unlikely, and probably not that useful to the non tech savvy, I was wondering if there was ever a removable storage device with a serial connection, yes, usb is technically serial, but I mean a chunky db9 connector you'd hook into the back of your computer and get a bit of portable storage with, basically just a massively old version of a flash drive.

Well, it didn't use flash memory, but a Digital Equipment TU58 DECtape II drive could store a whopping 256KB on a tape cassette, and had an RS232 interface.  I remember trying to use one to boot RT-11 on an LSI-11 system, and it was just about as frustrating as you would imagine.

Here's a company that built a TU58 emulator, using 29C040 flash memory: http://vakuum-servis.cz/tu58/?lang=en

[JacquesBBB]

An audio tape for the zx81 can be considered as a serial removable storage device.

Rate was 250 bauds.

[sleemanj]

Commodore 1541 disk interface is (a type of) serial.

Edit to add: Early digital cameras, and PDAs used to all be serial connection devices too which would almost fit the bill of serial-connected storage.

[NiHaoMike]

What about a MSP430 or similar microcontroller and a SPI Flash? You could embed a supercap that is charged off the data lines (expect a few mA per line) in order to supply the peaks needed to actually access the memory.

[Seekonk]

Whatever happened to bubble memory?  I have an early basic HP desk calculator.  That used a delay line as memory.

[Someone]

Some of the early MP3 players had a UART serial link for transferring files.

[crispy_tofu]

Obviously doesn't work, though.

[Galenbo]

... Early digital cameras, and PDAs used to all be serial connection devices too which would almost fit the bill of serial-connected storage.

I remember having one, no removable storage, only a proprietary connector, cable -to DB9.

An exe on top of Windows made transfer in both ways possible. After dinner, transfer was ready.

[Zbig]

Obviously doesn't work, though.

Ahh, the green (turquoise?) ones were pure evil! Several times I had to explain (usually unsuccessfully) to people that their random USB device won't work with those via their PCs' PS/2 ports just because the plug fits. Then I was on about the mouse it came with actually being a dual-interface device, and then getting blank stares followed by "but look, it fits, right...?"

[AlxDroidDev]

Early digital cameras, and PDAs used to all be serial connection devices too which would almost fit the bill of serial-connected storage.

Yeap! I still have my Handspring Visor, which uses a Serial interface (DB-9). It still works and I have the original box!

[timb]

Commodore 1541 disk interface is (a type of) serial.

Edit to add: Early digital cameras, and PDAs used to all be serial connection devices too which would almost fit the bill of serial-connected storage.

I thought the 1541 used IEEE-488 for transfer? Or am I thinking of an earlier Commodore machine?

[dreamwatcher]

Commodore 1541 disk interface is (a type of) serial.

Edit to add: Early digital cameras, and PDAs used to all be serial connection devices too which would almost fit the bill of serial-connected storage.

I thought the 1541 used IEEE-488 for transfer? Or am I thinking of an earlier Commodore machine?

The CBM serial bus was based on the IEEE-488/IEC-625 parallel protocol. Commodore went their own way when to came to external buses to the point there was no RS232 hardware in most Commodore hardware. One of the main advantages of this system allowed up to 32 devices to be daisy chained on the same serial bus.

For more detailed info:
https://www.c64-wiki.com/index.php/Serial_Port

[Kilrah]

Around 2000 when I had Internet access at my electronics school and spent the day in the lab, had no removeable storage (too expensive), but a 486 laptop scavenged from a dump I would download stuff to use later at home where I had no internet (usually in half an hour or so) onto the lab PC, then transfer it via serial to my laptop with hyperterminal (over approx. the rest of the day...) then reverse at home.
Does that count? 

[SeanB]

There was a device called a buffer box, used by serial devices like printers and PABX managers, which would store data going through it. In the print case you would send a massive burst of data at something like 115kbaud, while it would talk to the slow 80/132 column dot matrix line printer at a liesurely 9600 baud sending a line of print at a time for the printer to hammer onto the paper. Used so your print job would finish and come back to you within a second even though the printer would be spending the next 3 hours munching it's way through a big box of green/white tractor feed fanfold paper printing out whatever.

I used then on a PABX where it stored the data generated from the PABX so you could run the management software in the afternoon ( remember, in the days where Windows was still something you used to see if the sun was shining outside) to generate a listing of all calls made and update a billing database. Saved having to use a dedicated computer running this all the time ( though often it was so) to avoid missing data when the PABX 2 line buffer and the PC 2 byte buffer ( pre 16850 15 byte FIFO ) overflowed and lost data and gave garbled calls for a few lines.

[ElectricGuy]

Maybe something like this;
http://www.ebay.com/itm/UART-Flash-Disk-W-R-Controller-RS232-TTL-GPS-DATA-LOG-MCU-Master-Multifunction-/231183763072?hash=item35d3a04680:g:SloAAOxyoVZTKPT8

[Kevman]

A lot of old CNC machines use RS232 to load their programs. Way back in the day the company my dad works for used an Epson HX-20, carrying it from machine to machine loading programs off of microcassette. They would have probably killed for something like you describe- but these things had relatively large programs so what would you have stored the data on beyond a tape or disk drive?

Today they use box called (I think) shop-link that uses Ethernet to connect a server. I repaired one once- its basically a phone SoC and a pile of MAX232s. You tell the server what type of CNC is connected to each port and then which a list of programs each each machine sees... Then the CNC machine queries the list using whatever protocol and the operator at the machine can pick off of the list.

I'm pretty sure they still have a few machines running with bubble memory. I know they got rid of their last machine with a paper tape drive less then 5 years ago, though they hadn't used the drive in many many years- that's what RS232 is for!

[kingofkya]

Some of the early MP3 players had a UART serial link for transferring files.

minolta digital camera also used to do that the ones in the 2megapixels or less range. Had a serial and usb1.0 adaptor(just a usb  serial adaptor)

 That thing used to destroy batteres 6-10 pictures before they over heated and you needed new ones.

[calexanian]

I remember some cartridge tape backup drives being serial. I actually just looked them up. It would appear that bulk tape backup is still a thing and systems upwards of 1000 TB are in use. I would have figured bulk flash would have brought tape backup to an end.

[XOIIO]

I remember some cartridge tape backup drives being serial. I actually just looked them up. It would appear that bulk tape backup is still a thing and systems upwards of 1000 TB are in use. I would have figured bulk flash would have brought tape backup to an end.

I have a tape autoloader, it only works with either 100gb/200gb compressed tapes, or maybe 200/400, but I think they are just more of a standard, and can survive for quite a long time for archival backup. I'm hoping I can get it working, and maybe upgrade the drive on it as these earlier/lower capacity tapes are actually quite cheap nowadays. The new tapes are massively expensive, and impressive.

[rrinker]

A lot of old CNC machines use RS232 to load their programs. Way back in the day the company my dad works for used an Epson HX-20, carrying it from machine to machine loading programs off of microcassette. They would have probably killed for something like you describe- but these things had relatively large programs so what would you have stored the data on beyond a tape or disk drive?

Today they use box called (I think) shop-link that uses Ethernet to connect a server. I repaired one once- its basically a phone SoC and a pile of MAX232s. You tell the server what type of CNC is connected to each port and then which a list of programs each each machine sees... Then the CNC machine queries the list using whatever protocol and the operator at the machine can pick off of the list.

I'm pretty sure they still have a few machines running with bubble memory. I know they got rid of their last machine with a paper tape drive less then 5 years ago, though they hadn't used the drive in many many years- that's what RS232 is for!

 Way back when at my first post-college job, I worked with a company that developed a system for CNC shops. Their unit was a hardened case terminal with a 4 line LCD display (I think I am remembering this correctly) and a membrane keypad, so impervious to oils and coolant and other stuff on the shop floor. It has 2 RS-232 ports on it, one connected to the CNC controller's serial port, the other was strung through the shop to a distribution box that hung on the wall., This in turn was connected via another serial cable to the computer that held all the CAM files. Each box was limited to only be able to select the files that belonged on that particular machine, so the operator of a lath couldn't download the programs for the vertical mill, or anything like that. We did take one apart, but they had sanded off the markings on the main chips being used.

 The computer consultant there and I came up with an idea to use Ethernet instead of serial. We came up with most of the general aspects of the design and presented it to my university's new automated manufacturing and robotics department, but nothing ever came of it. Probably others had also already had the same idea.

 Years later I went to do some work in my current capacity as a computer consultant for this company, the name sounded familiar, and when I related my experience with that old system, they were like, yes, that was us. Their current systems use Ethernet, no more serial cables all over the shop.

[KL27x]

Does SCSI count? I had this thing called a Zip Drive that took Zip Discs. It was practical for about 6 months.

[uncle_bob]

Hi

Paper tape reader on an ASR 33 comes to mind. If that's not old enough, the earlier stuff used 5 level tape on ASR-28's. That was back in the mid 1950's. If non-computer use counts, paper tape goes back to the 1800's. It was all serial back then.

Bob

[tom66]

The closest is probably the Rio PMP300, widely regarded as the first commercially successful MP3 player. It used a parallel port for data transfer.

https://en.wikipedia.org/wiki/Rio_PMP300

[timb]

Does SCSI count? I had this thing called a Zip Drive that took Zip Discs. It was practical for about 6 months.

Scuzzy is a parallel interface. External Zip drives came in both Parallel Printer Port and SCSI interface variants.

Keep in mind that, in the 80's, serial was very, very slow; the first UARTs (original 8250) combined with an XT class machine could barely work up to 4800bps due to the amount of interrupts it generated, while the 16450 (on a PC/AT class machine) could only reliably do 9600bps (maybe 14.4Kbps+ if you used a protocol with error detection like Kermit or Zmodem).

In the early 90's, the 16550 was released, which had a 16 byte FIFO and could generate interrupts at 1, 4, 8 or 14 byte intervals. Unfortunately the original 16550 had an issue where the FIFO didn't work; this was corrected in the 16550AF silicon, circa 1992.

The 16550 is pin *and* software compatible with the 8250/16450, meaning you can replace the factory UART in old XT/AT class machines. The 16550's registers will look like an 8250 until a command is given, then it will go into 16550 mode; this way it even works with old software.

Using a 16550, you could reliably do 115.2Kbps over serial. Some ISA Serial Port cards with 16550 (and '650, '750, '850, etc.) UARTs allow you to set a clock multiplier, so you can even reliably do up to 460.8Kbps! (Which is nearly as fast as a vintage 5.25" floppy drive.)

In fact, the XTIDE Universal Bios (which is a bios extension that allows you to run large hard drives / flash storage on vintage machines) has a feature that allows you to boot from a virtual floppy or hard drive over serial. You run the server software on a Windows/Linux/OS X machine, select the imagine and boot the target, when XTIDE loads you hit a key and it try's to access the image via the serial port. It's very useable for loading a fresh copy of DOS on a new machine, even at 115.2Kbps! (Though it would be a bear at 9600bps...)

Anyway, my point is that for a 1980's class machine, without a 16550 UART, using the serial port for storage is going to be painfully, painfully slow. It's doable, but even an original non-EPP Parallel Port would be better (which is 8-bits write, 4-bits read).

[bitslice]

Something I've only just discovered is that modern hard drives have a serial connection on them, you can connect to it and do some basic testing of the drive.

I'd like to find out if that includes writing to sectors or not.

[Rick Law]

TRS80, Atari 400 and Atari 800 all had audio cassette tape based storage devices.  It "talks" the bits like a modem.  The computer "reads", the tape device plays it back.  I had one of those for my Atari 800 in addition to my floppy.

I am rather sure but not positive that the commodore has it also.

[uncle_bob]

Anyway, my point is that for a 1980's class machine, without a 16550 UART, using the serial port for storage is going to be painfully, painfully slow. It's doable, but even an original non-EPP Parallel Port would be better (which is 8-bits write, 4-bits read).

Hi

Having loaded a *lot* of code at home via paper tape ... even 110 baud is *fast* compared to how quickly you can type it in.

It's all a matter of what you are used to.

Bob

[timb]

Anyway, my point is that for a 1980's class machine, without a 16550 UART, using the serial port for storage is going to be painfully, painfully slow. It's doable, but even an original non-EPP Parallel Port would be better (which is 8-bits write, 4-bits read).

Hi

Having loaded a *lot* of code at home via paper tape ... even 110 baud is *fast* compared to how quickly you can type it in.

It's all a matter of what you are used to.

Bob

Yes, but there's a difference between a few kilobytes of data and megabytes of it. (An order of magnitude, in fact!)

I remember the days when I had a 2400bps modem, logging onto the local BBS. It took an *hour* to download a single low resolution bitmap (the current NOAA satellite weather map), which was only a few KB. It would take two or three nights sometimes just to download the latest shareware game.

Anyway my point is, for a few text files a serial port thumb drive might be doable, but for anything else it's just not feasible. Doubly so if the OP wants to do it with legacy technology only available in 1984. Because then you're not only stuck with 1200bps transfer speeds, but you're also very limited to the memory you can use; either a couple of KB of SRAM + backup battery, or 256Kbit of EPROM + UV eraser.

The reason such a thing was never made is because floppy disks basically struck a perfect balance for the time: They could hold a lot of data, were fairly reliable and faster than the alternatives.

[dreamwatcher]

TRS80, Atari 400 and Atari 800 all had audio cassette tape based storage devices.  It "talks" the bits like a modem.  The computer "reads", the tape device plays it back.  I had one of those for my Atari 800 in addition to my floppy.

I am rather sure but not positive that the commodore has it also.

Yep, the C2N or VIC 1530.

The C64 wiki again has some good information:

https://www.c64-wiki.com/index.php/Cassette_Port

https://www.c64-wiki.com/index.php/Datasette

In case some are wondering, part of my business is restoring and electronic modification of vintage computers/game consoles. The C64 was the computer I cut my teeth on in my Jr. high-high school years,  and I still have a soft spot for it. 

[uncle_bob]

Anyway, my point is that for a 1980's class machine, without a 16550 UART, using the serial port for storage is going to be painfully, painfully slow. It's doable, but even an original non-EPP Parallel Port would be better (which is 8-bits write, 4-bits read).

Hi

Having loaded a *lot* of code at home via paper tape ... even 110 baud is *fast* compared to how quickly you can type it in.

It's all a matter of what you are used to.

Bob

Yes, but there's a difference between a few kilobytes of data and megabytes of it. (An order of magnitude, in fact!)

I remember the days when I had a 2400bps modem, logging onto the local BBS. It took an *hour* to download a single low resolution bitmap (the current NOAA satellite weather map), which was only a few KB. It would take two or three nights sometimes just to download the latest shareware game.

Anyway my point is, for a few text files a serial port thumb drive might be doable, but for anything else it's just not feasible. Doubly so if the OP wants to do it with legacy technology only available in 1984. Because then you're not only stuck with 1200bps transfer speeds, but you're also very limited to the memory you can use; either a couple of KB of SRAM + backup battery, or 256Kbit of EPROM + UV eraser.

The reason such a thing was never made is because floppy disks basically struck a perfect balance for the time: They could hold a lot of data, were fairly reliable and faster than the alternatives.

Hi

My main point was ... yes serial storage was once *very* common. It was the way "it was done" for many decades. It was king until what we have today came along.

Yes, it died for a reason.

Bob

[Rick Law]

...
...
Yes, but there's a difference between a few kilobytes of data and megabytes of it. (An order of magnitude, in fact!)
...
...

Unless EE folks do it different, a kilo and a mega is 3 orders of magnitude difference

[SeanB]

If you want serial memory Mostek used to make it, in a bucket brigade delay line which had some odd requirements ( like all BBD devices) for supply voltage, clock overlap and power supply sequencing. IIRC a whole 513 bits of storage, serial in and serial out, with a recirculate control and a tap at 512 and 513 as well.

[Andreas]

Short answer: yes I have one.

Unknown manufacturer. obviously 1986.

Giant memory of 64 kBit NiCd battery backed up RAM.
Memory write protection with REED relay.
Modern National Semiconductor SC/MP II microcontroller.
Serial interface DB25S switchable between 1200 / 4800 Baud with DIP-switches.
DIP switch selectable hand-shake and read / write mode.

Afaik it was used to transfer data for diploma from PC at work to Apple ][+ at home and back.

with best regards

Andreas

[timb]

...
...
Yes, but there's a difference between a few kilobytes of data and megabytes of it. (An order of magnitude, in fact!)
...
...

Unless EE folks do it different, a kilo and a mega is 3 orders of magnitude difference

<pedantic mode>
Well I didn't specify exactly how much data, so it could be from one to six orders of magnitude difference: 1 Megabyte is 10^6 and 100 Kilobytes is 10^5; 1 Kilobyte is 10^3 and 100 Megabytes is 10^8.

This is all assuming 1000 bits = 1 byte. If we go by kibibytes and mebibytes (1024 bits = 1 byte) it stretches from 2^13 to 2^32.
</pedantic mode>

I guess I should have said, "At least an order of magnitude, in fact."

[Rick Law]

...
...
Yes, but there's a difference between a few kilobytes of data and megabytes of it. (An order of magnitude, in fact!)
...
...

Unless EE folks do it different, a kilo and a mega is 3 orders of magnitude difference

<pedantic mode>
Well I didn't specify exactly how much data, so it could be from one to six orders of magnitude difference: 1 Megabyte is 10^6 and 100 Kilobytes is 10^5; 1 Kilobyte is 10^3 and 100 Megabytes is 10^8.

This is all assuming 1000 bits = 1 byte. If we go by kibibytes and mebibytes (1024 bits = 1 byte) it stretches from 2^13 to 2^32.
</pedantic mode>

I guess I should have said, "At least an order of magnitude, in fact."

Actually, I did wonder if EE guys do it different.  With "Engineering notation", stuff is expressed as 10^n where n is in increment of three, whereas "Scientific notion" has n in increment of one.  So, across fields of study, one can never be sure.

I was in Physics and long time ago, I had a confusing conversation with a Nutritionist.  Deep into the conversation I realized that 1 Calorie to a nutritionist is 1000 calorie to a Physicist.

Physics:
1 calarie = 1gm of water heat up 1 degree C

Food:
1 Calarie = 1kg of water heat up 1 degree C

They (nutritionist) always spell it with a capital C, but that is still damn confusing.

[PA0PBZ]

Brother FB-100.

3.5" portable disk drive with RS232 interface, primarily used for knitting machines.

[uncle_bob]

...
...
Yes, but there's a difference between a few kilobytes of data and megabytes of it. (An order of magnitude, in fact!)
...
...

Unless EE folks do it different, a kilo and a mega is 3 orders of magnitude difference

<pedantic mode>
Well I didn't specify exactly how much data, so it could be from one to six orders of magnitude difference: 1 Megabyte is 10^6 and 100 Kilobytes is 10^5; 1 Kilobyte is 10^3 and 100 Megabytes is 10^8.

This is all assuming 1000 bits = 1 byte. If we go by kibibytes and mebibytes (1024 bits = 1 byte) it stretches from 2^13 to 2^32.
</pedantic mode>

I guess I should have said, "At least an order of magnitude, in fact."

Actually, I did wonder if EE guys do it different.  With "Engineering notation", stuff is expressed as 10^n where n is in increment of three, whereas "Scientific notion" has n in increment of one.  So, across fields of study, one can never be sure.

I was in Physics and long time ago, I had a confusing conversation with a Nutritionist.  Deep into the conversation I realized that 1 Calorie to a nutritionist is 1000 calorie to a Physicist.

Physics:
1 calarie = 1gm of water heat up 1 degree C

Food:
1 Calarie = 1kg of water heat up 1 degree C

They (nutritionist) always spell it with a capital C, but that is still damn confusing.

Hi

The main confusion is the subtle point of K being a thousand. Is that a nice decimal 1,000 or is it a round binary 1024 (2^10) . The confusion carries on up the "engineering notation" scale. Every single disk drive that has ever been reviewed will have a loud complaint from somebody who has never noticed this before. The same complaint has been showing up since the 1970's. Obviously it has been a stumbling block for a lot of people.

Bob

[Rick Law]

...
...
The main confusion is the subtle point of K being a thousand. Is that a nice decimal 1,000 or is it a round binary 1024 (2^10) . The confusion carries on up the "engineering notation" scale. Every single disk drive that has ever been reviewed will have a loud complaint from somebody who has never noticed this before. The same complaint has been showing up since the 1970's. Obviously it has been a stumbling block for a lot of people.

Bob

You may be right.  We here understood why computer stuff use 2^n, but most computer/phone buyer probably don't know that their 32GB is really not 32,000,000,000 bytes.

Also, they only used to carry that 1024 all the way up the scale.  During the early days of the Gigabyte drives, I recalled 1gb used to be 1024mb; but for marketing reasons the manufacturer switched and cut that off.  So instead of 1gb=1024 mb, they begin using 1gb=1000mb while 1mb still use 1024kb.

[timb]

...
...
The main confusion is the subtle point of K being a thousand. Is that a nice decimal 1,000 or is it a round binary 1024 (2^10) . The confusion carries on up the "engineering notation" scale. Every single disk drive that has ever been reviewed will have a loud complaint from somebody who has never noticed this before. The same complaint has been showing up since the 1970's. Obviously it has been a stumbling block for a lot of people.

Bob

You may be right.  We here understood why computer stuff use 2^n, but most computer/phone buyer probably don't know that their 32GB is really not 32,000,000,000 bytes.

Also, they only used to carry that 1024 all the way up the scale.  During the early days of the Gigabyte drives, I recalled 1gb used to be 1024mb; but for marketing reasons the manufacturer switched and cut that off.  So instead of 1gb=1024 mb, they begin using 1gb=1000mb while 1mb still use 1024kb.

As a general rule, memory has always been 2^n and magnetic storage is 10^n. That's why we now have kibi, mebi, gibi, tebi, etc. It's a portmanteau of Kilo (or Mega, Giga, Tera) and Binary, so it makes a lot of sense even though I think they're a bit awkward to pronounce.

The big problem is JEDEC still isn't completely onboard! They still define 2^n as Kilo instead of Kibi...

[Towger]

This thread is making me feel old.

[eas]

The Atari 400/800 used an, apparently proprietary, addressable serial bus for connecting peripherals, including their floppy drive.

[stmdude]

TRS80, Atari 400 and Atari 800 all had audio cassette tape based storage devices.  It "talks" the bits like a modem.  The computer "reads", the tape device plays it back.  I had one of those for my Atari 800 in addition to my floppy.

I am rather sure but not positive that the commodore has it also.

Yep, the C2N or VIC 1530.

The C64 wiki again has some good information:

https://www.c64-wiki.com/index.php/Cassette_Port

https://www.c64-wiki.com/index.php/Datasette

In case some are wondering, part of my business is restoring and electronic modification of vintage computers/game consoles. The C64 was the computer I cut my teeth on in my Jr. high-high school years,  and I still have a soft spot for it. 

Actually, the disk-drives were serial as well.  There is even a very obscure hard-drive for the VIC20/C64/C128 called the HD-20, which also connects serially to the computer.