Date: Mon, 13 Apr 1998 19:31:11 +0100 (BST) Reply-To: classiccmp@u.washington.edu Sender: CLASSICCMP-owner@u.washington.edu Precedence: bulk From: Tony Duell <ard@p850ug1.demon.co.uk> To: "Discussion re-collecting of classic computers" = <classiccmp@u.washington.edu> Subject: Re: 5150 was Re: Asshole bites the dust

> Did IBM ever really put out a cassette for the 5150's ? Knowing = "Big Blue"=20 > that must have been a very impressive and expensive tape-mchn. How = was this

I don't know if IBM ever sold a cassette recorder for the PC, but the=20 port certainly existed. I believe the original idea was for the owner to =

pop down to a Radio Shack store and buy a cassette recorder (more = details=20 below).

I've got a PC techref here...

OK, this what the port consists of :=20

Most of the work was done in software.

Write : The output of the 8253 channel 2 (the one used for the speaker =

as=20 well) was inverted and put on a voltage divider. The output of said =

voltage=20 divider went to the microphone or aux input of the cassette recorder.

Read. The earphone output of the cassette recorder went to an 741-based=20 amplifier. The output of that was clipped to TTL levels and went to port =

PC4 on the 8255. You read it at bit 4 of port 0x62.

Bit PB3 of the 8255 (port 0x61, bit 3) is bufferd and used to drive a=20 relay coil. _Clearing_ this bit turns the relay on. The relay contacts=20 control the cassette motor. In typical IBM self-diagnostic style, =

another=20 set of contacts on the relay disconnects the input of the read amplifier =

from the cassette earphone socket and connects it to the output votlage=20 divder, allowing the system to check the read amplifer, when the = cassette=20 motor is turned off.

You use the cassette via BIOS interrupt 0x15.

AH=3D0 turns on the cassette motor.=20

AH=3D1 turns it off.=20

AH=3D2 reads a tape block. Number of bytes to read is passed in CX, = start=20 address of the buffer to read them into in ES:BX. It returns with the=20 actual number of bytes read in DX, carry set if error occured, status in =

AH, ES:BX =3D last byte trasnfered + 1.=20 The status is given by AH=3D1 for CRC error, AH=3D2 for lost data, = AH=3D4 if no=20 data found.

AH=3D3 writes a tape clock of CX bytes starting from ES:BX. On exit, = CX=3D0,=20 ES:BX =3D last byte transfered + 1

AH=3D anything else returns AH=3D0x80 - illegal command.

I can provide the format of the data on the tape if you want it.

The port was useable from BASIC. There were commands MOTOR ON and MOTOR=20 OFF to operate the relay and SAVE and LOAD to transfer programs in ROM=20 BASIC. I can't remember how you used the cassette from disk BASIC.

One other interesting thing is the pinout of the cassette port = (numbering=20 the pins conventionally ) :=20

1 Motor Control 2 Ground 3 Motor Control 4 Data In (to PC) 5 DAta Out (from PC)=20

That's _exactly_ the same as the pinout of a TRS-80 cassette port. I'm=20 pretty sure the original intention was to use a Radio Shack cable.

> port accessed ? Does anyone know what " hacks" were done or = possible on > this I/O ?

The most trivial hack was to use the motor relay to switch some other=20 low-voltage device - like a small lamp. I've done that.

-tony

Date: Tue, 14 Apr 1998 08:46:45 -0700 Reply-To: classiccmp@u.washington.edu Sender: CLASSICCMP-owner@u.washington.edu Precedence: bulk From: David Wollmann <dwollmann@ibmhelp.com> To: "Discussion re-collecting of classic computers" = <classiccmp@u.washington.edu> Subject: Cassette BASIC in IBM PCs

Here's one I've never run into, oddly enough. IBM PCs 5150 throrugh 5170 had the BASIC ROM and BASIC.EXE and BASICA.EXE included with PC-DOS = through 4.0 just jump to the code on the ROM.

Later models (PS/2s) still have the Cassette BASIC, but don't seem to be able to run the PC-DOS BASICs. Did IBM break the BASIC ROM after the = 5170 model?

--
David Wollmann | dwollmann@ibmhelp.com | Support for legacy IBM products. DST ibmhelp.com Technical Support | Data, document and file conversion = for IBM http://www.ibmhelp.com/ | legacy file and media formats.

Date: Fri, 17 Apr 1998 22:05:50 -0700 Reply-To: classiccmp@u.washington.edu Sender: CLASSICCMP-owner@u.washington.edu Precedence: bulk From: David Wollmann <dwollmann@ibmhelp.com> To: "Discussion re-collecting of classic computers" = <classiccmp@u.washington.edu> Subject: Re: 5150=20

At 09:24 PM 4/16/98 +0000, you wrote: >On 15 Apr 98 at 1:05, Tony Duell wrote: > [snip] >> Did any of the clones of the Async card have the current loop = interface?=20 >> For that matter, did anyone ever use it for anything? >>=20 >> -tony >>=20

The IBM Displaywriter PC Attach Convenience Kit (for document transfer between PC or PCjr and Displaywriter word processor) included a serial cable with a standard RS-232 connector to the PC async (actually has the PCjr-style connector with an adapter for use with the PC) and a big fat connector on the Displaywriter end, that actually includes a mini async card inside. The manual for the PCACK warns that the IBM Async adapter = with current loopback mode enabled is required to make it work right. I = didn't think the PCjr supported loopback though. It's been some time since I = used the cable to transfer documents and I haven't seen the dox in years.

[snip] > In exploring the programs on the 5150's Hard-card I found two small = programs >from the same company (PLUS) that made the hardcard. One was = light.com and the=20 >other sound.com parameters were light=3D on/ off , and sound =3D on = / off . Since=20 >the h-c itself had no external connectors, I'm wondering whether = these are for=20 >the cassette port.

I think light was used to simulate a drive access LED on the display.

>This 5150 was also configured for 2 serial and 2 parallel >which would square with the serial / para on the int.modem and the = printer port\ >on the Herc. leaving one serial unaccounted for. The only other = connector is=20 >the f 37 pin ext. on the fdd controller card. ( for an external = drive ? )

Exactly, external 360K.

>QUE's=20 >Upgrading and Repairing P.C.'s v.5 (BTW an excellent book with the = most=20 >extensive info on PS2 s I've seen -V.5 only) doesn't mention this = port tho it=20 >has a lot of detail on the 5150 and adapter cards.

We use the Mueller books here quite a lot--we stopped buying them after = 4 ed. when he dropped the IBM PS lines from the specs section--oddly = enough, the Family Ones (PC, XT, AT, etc.) are still covered in the latest (8?). = 3 and 4 both have sections that show the different connector types one is likely to encounter, and the 37-pin external floppy port is listed = there. He probably dropped it from the later editions to save space.

> >ciao larry=20 > >lwalker@interlog.com >

Date: Sat, 18 Apr 1998 23:07:27 +0100 (BST) Reply-To: classiccmp@u.washington.edu Sender: CLASSICCMP-owner@u.washington.edu Precedence: bulk From: Tony Duell <ard@p850ug1.demon.co.uk> To: "Discussion re-collecting of classic computers" = <classiccmp@u.washington.edu> Subject: Re: 5150

I > In exploring the programs on the 5150's Hard-card I found two = small programs > from the same company (PLUS) that made the hardcard. One was = light.com and the=20 > other sound.com parameters were light=3D on/ off , and sound =3D = on / off . Since=20 > the h-c itself had no external connectors, I'm wondering whether = these are for=20 > the cassette port. This 5150 was also configured for 2 serial and 2 = parallel

I'd guess that those programs were simply to provide some means of=20 knowing when the hardcard was being accessed. Possibly by either turning =

on a graphics block in the corner of the screen or by making some kind = of=20 sound through the PC's speaker. Have you tried them?

> on the Herc. leaving one serial unaccounted for. The only other = connector is=20 > the f 37 pin ext. on the fdd controller card. ( for an external = drive ? ) QUE's=20

It's for 2 external 360K (or 720K, unofficially) floppy drives. My XT = has=20 2 360K drives in the case and 2 720K ones externally.=20

I can look up pinouts if you need them, but I seem to remember that all=20 you need to do is take a standard PC floppy cable (with the twist),=20 remove the controller connector and crimp on a DC37-P plug (IDC = version).=20 Do that so that pins 1,2,20 are not used and so that the marked edge of=20 the cable goes to pin 21 (nearest the top of the machine when it's=20 plugged in). That's it.

> Upgrading and Repairing P.C.'s v.5 (BTW an excellent book with the = most=20 > extensive info on PS2 s I've seen -V.5 only) doesn't mention this = port tho it=20 > has a lot of detail on the 5150 and adapter cards.

I've looked at a lot of those books and come to the same conclusion. = They=20 miss out so much information compared to the IBM manuals (like=20 schematics, ROM sources, etc) that they're a waste of money. I'll stick=20 to my 'mini purple wall' :-)

>=20 > ciao larry=20

-tony

Date sent: Fri, 22 May 1998 21:48:07 -0400 Send reply to: classiccmp@u.washington.edu From: Ward Donald Griffiths III <gram@cnct.com> To: "Discussion re-collecting of classic computers" = <classiccmp@u.washington.edu> Subject: Re: Prices to pay for old computers...

Julian Richardson wrote:

> back on topic though, what cassette unit could be connected up to = the > original PC machines? Was it a custom IBM unit only (similar to the = way > the C64's only accept Commodore tape decks), or could anything be = used > if a cable was made up?

A Radio Shack CTR-41 with a standard TRS-80 cassette cable. IBM never got into the audio business. (There were other cassette decks that worked, but that was the cable -- after all these years I've forgotten the stock number but it is still in the inventory though a particular store might have to make a special order). -- Ward Griffiths

Date sent: Fri, 29 May 1998 20:02:11 +0100 (BST) Send reply to: classiccmp@u.washington.edu From: ard@p850ug1.demon.co.uk (Tony Duell) To: "Discussion re-collecting of classic computers" = <classiccmp@u.washington.edu>=7F Subject: Re: Original IBM PC (was Re: Prices to pay for old

[IBM PC floppy drives]

> I get nothing out of them, no motor spin up, no led, no > nothing...................

I've got the Type 1 drive schematics here (from the O&A TechRef = volume 1).

Let's go through the obvious things first.

You have a DIP shunt (a little plastic block with shorting bars) in socket 1E of both drives, right? And a termination resistor pack in socket 2F of the drive physically furthest from the controller.

Check that the cables on J4 at the back of the logic board are connected properly. There are some blank pins (4?) nearest to the edge connector, and then P8-P12 in order along the pins.

Also, check the supply voltages - +5V and +12V at the drive when the machine is turned on. You do have the power cables plugged in, I trust :-) (don't laugh - I've forgotten them).

OK, let's sort out the lack of LED first. Unplug the cable from the controller (leave it hooked up to the drives) and turn on the machine.

Ground pin 3 of IC 3E (a 7407) in the drive. Does the LED come on now? = If so, then suspect the controller, DIP shunt or cable. If not, then ground pin 4 of IC3E. If the LED now comes on, then IC3E is defective (or not geting power).

Problem is, if IC3E is defective, then how many other parts have been damaged. 7407's are pretty reliable, so if it's damaged, it sounds like power problems. You didn't hook up the power cable backwards, did you?

You can trace the motor on signal similarly. Try grounding pin 16 on the edge connector (the even numbered pins are on the top of the board, starting from the end nearest to the notch in the connector tongue), or equivalently pin 1 of IC3E. If the motor doesn't start,then try = grounding TP13. If that starts the motor, IC3E is defective. If the motor still doesn't start then I'll have to talk you through the motor control board at the back.

> > >

-tony