• Please review our updated Terms and Rules here

I assume that the 74LS181 (not 74181) didn't became common....

Hugo Holden

Veteran Member
Joined
Dec 23, 2015
Messages
4,570
Location
Australia
. Some of that stuff ran *hot*.


A while back I made a "logic probe" that converts 16 Binary bit into Decimal on a display, it has a very short latency of only 350nS and it can latch the data too. I made it because the binary data lines on a project I was working on was messing with my head and I decided to slow it right down and watch it count in decimal, to make sure there were no errors. To do this I used the rare and very vintage power hungry 74185 IC's with 72 & 73 date codes and had a custom board made. These IC's have the hard resinous plastic packages typical of early TI IC's and they were cut off at their ends, with cutting disc marks, typical of early TI IC packages. The power supply board uses 1/8" thick fiberglass fitted with eyelets. The housing is made by Takachi.

In any case, I significantly underestimated the total thermal dissipation inside the case and this resulted in the failure of one IC and one display module. So I had to place ventilation holes above the displays in the case and a cooling fan in the bottom to keep the internal case and IC temperatures respectable.

The 74185 is a very interesting and now harder to get IC.

Of course the whole thing could have been done with a uP and LCD display and run as cool as a cucumber, but where is the fun in that.
 

Attachments

  • BINARYDEC2.jpg
    BINARYDEC2.jpg
    780.3 KB · Views: 13
  • BINARYDEC3.jpg
    BINARYDEC3.jpg
    175.2 KB · Views: 13
  • bindec6.jpg
    bindec6.jpg
    240.8 KB · Views: 12
  • bindec7.jpg
    bindec7.jpg
    195.4 KB · Views: 12
  • bindec5.jpg
    bindec5.jpg
    226.1 KB · Views: 12

Chuck(G)

25k Member
Joined
Jan 11, 2007
Messages
43,978
Location
Pacific Northwest, USA
Believe me, I've looked for those. Virtually unobtainium today. But a great IC. On the other hand, someone has the TRW 16x16 multiplier in stock--only $300. Yet the AMD version is only $35 on eBay.

I wonder if the Moto MC10800 ECL ALU is any easier to find. I suspect not.
 
Last edited:

yuhong

Experienced Member
Joined
Mar 2, 2010
Messages
359
... Here's with a real example of what you're stuck with if you only have TTL:

Here are the schematics for a Wang 2200 computer that sold for $7,400 in 1973 money (That's about $50,000 today) for a minimal 4K system. (more about the Wang) This machine uses a single 74181 on its ALU board, and all together it looks like what we'd call the "CPU" (if we were comparing it to an 8080 or something) is spread across around six boards. It was clocked at 10mhz, but took around 16 cycles to complete most "microinstructions", which weren't really comparable to the "visible" instructions on a normal CPU; many microinstructions were necessary for even the simplest operation. In other words, this baby was pretty slow despite its relatively high input clock speed, and it lived inside a giant metal suitcase cabled to a power supply about the size of a microwave oven. (the terminal was separate) Switching from "straight" TTL to LS sped the machines up significantly and get rid of the microwave oven power supply; by 1976 denser memory devices finally enabled them to offer a low end "PCS" model that fit inside of a (very fat) desktop terminal case. (Although arguably the main line remained the giant suitcases, which started incorporating systems to support multiple terminals and act like baby Minicomputers.)

Anyway, this 1976 "portable" Wang still weighed a ton and cost $5400 for an 8K computer. (FWIW, this was considered "cheap" compared to the 16K configuration of the competing IBM 5100, which was priced at a cool $8,975.) At this point you could get a microcomputer of roughly similar capabilites for around a third of that price (including a monitor ), and by the end of 1977 the Wang would be competing with $599 TRS-80s. It's hard to compare the absolute performance of the Wang machines to early microprocessor-powered PCs because the Wang computers could literally only run BASIC; it was baked into their microcodes, but for most practical purposes they were "similar", maybe for some BASIC programs the Wang could be faster than a cheap micro running a software BASIC, but you can see how this isn't even a contest at this point in terms of "bang for the buck".

(Wang themselves baked their TTL CPUs into proprietary VLSI chips by the early 80's, essentially turning them into microcomputers, to get the margins up. And by the late 80's they started selling their legacy customers a system that had a 386 CPU in it running a software version of their BASIC "microcode", because at this point they were too niche to keep developing hardware themselves..)

Anyway, you can see how there is *no way* we would have had a "home computer revolution" in the 1970's with the cheapest machines costing as much as Cadillacs. (Or even houses.) Getting the scale of integration up was the only way that was ever going to bring the price down enough for that to happen.
Though early microprocessors were expensive as well. It took until MOS Technology 6502 for the cost to come down.
 

Eudimorphodon

Veteran Member
Joined
May 9, 2011
Messages
6,738
Location
Upper Triassic
Though early microprocessors were expensive as well. It took until MOS Technology 6502 for the cost to come down.

Do you think that all the pieces to make a bit-slice equivalent would be cheaper? The microcode PROMs alone were probably more than the *list* price of an 8080, and nobody paid list. (Initial list was $360 quantity one, but MITS paid $75 a piece for the Altair 8800.)
 

pbirkel@gmail.com

Veteran Member
Joined
Apr 7, 2013
Messages
1,082
Location
Silver Spring, MD, USA
... Here's with a real example of what you're stuck with if you only have TTL:
A second example is the 16-bit Data General Nova 1200 which used a single 4-bit 74181 to implement a 16-bit processor on a 15x15" PCB (~120 ICs): https://en.wikipedia.org/wiki/File:Data_General_Nova_1200_CPU.agr.jpg

A second 15x15" PCB added 4 (or more) Kword core memory. And if you wanted I/O with that, a third 15x15" PCB (variously populated depending on your I/O requirements -- most commonly at the start that would be a 20mA serial interface with TTY punch control plus a high-speed paper tape reader-punch).

Can't get very far with just a lone 74181 if you want to accomplish much in the real world! A great chip, no doubt. But ...
 

stepleton

Veteran Member
Joined
Jan 1, 2020
Messages
517
Location
London, UK
Just to list another example: PERQ 2s (and I'm guessing PERQ 1s) had five 74S181s to make up a 20-bit ALU, per the schematic (PDF pages 15-16). I sure hope the ones in my malfunctioning PERQ aren't what's wrong, as I'm not sure where I'd find replacements.
 

NeXT

Veteran Member
Joined
Oct 22, 2008
Messages
8,056
Location
Kamloops, BC, Canada
Just to list another example: PERQ 2s (and I'm guessing PERQ 1s) had five 74S181s to make up a 20-bit ALU, per the schematic (PDF pages 15-16). I sure hope the ones in my malfunctioning PERQ aren't what's wrong, as I'm not sure where I'd find replacements.
A PERQ will malfunction simply by existing. That is one of the few machines you can rebuild from scratch and it will still crash the moment you look away.
 

MattisLind

Veteran Member
Joined
Sep 30, 2013
Messages
1,153
Location
Stockholm, Sweden
Speaking of bit-slice. What about the Intel 3001/3002? How many designs used those two-bit slices? I don’t think I know of any.
Second sourced by Signetics. I have a bunch of N3002 chips That I bought very chip in the late 80ies.

Signetics also second sourced the 8x300. Was it Signetics who then evolved it into 8x305? I have a bunch of those odd 50 pin chips. Those at least I have seen live in various disk controllers.
 

MattisLind

Veteran Member
Joined
Sep 30, 2013
Messages
1,153
Location
Stockholm, Sweden
A PERQ will malfunction simply by existing. That is one of the few machines you can rebuild from scratch and it will still crash the moment you look away.

My ICL PERQ 2 T2 used to work fine until last time I tried it. Then the mouse/digitizer refused to work. Not sure if this was some kind of problem in the digitizer itself or the PERQ. It starts up the Metaform program but I don’t see any mouse pointer and nothing happes when I try to move the mouse. Need to figure that out somehow.
 

Chuck(G)

25k Member
Joined
Jan 11, 2007
Messages
43,978
Location
Pacific Northwest, USA
Speaking of bit-slice. What about the Intel 3001/3002? How many designs used those two-bit slices? I don’t think I know of any.
Second sourced by Signetics. I have a bunch of N3002 chips That I bought very chip in the late 80ies.

Signetics also second sourced the 8x300. Was it Signetics who then evolved it into 8x305? I have a bunch of those odd 50 pin chips. Those at least I have seen live in various disk controllers.
The 8X300 was not bit-slice--just a bipolar early microcontroller. Mostly used in hard disk controllers, but you could find it scattered here and there. There was also a companion floppy controller chip and various other "extension" chips. Being bipolar, it runs hot as a pistol. You can pick it out from 10 feet on a board--there's always a series-pass regulator transistor nearby.

Intel used its 3000-series bitslice in its floppy controller on the MDS-800.
 

Eudimorphodon

Veteran Member
Joined
May 9, 2011
Messages
6,738
Location
Upper Triassic
A second example is the 16-bit Data General Nova 1200 which used a single 4-bit 74181 to implement a 16-bit processor on a 15x15" PCB (~120 ICs):

It is of course notable that the only reason it even manages to be this small is the Nova 1200 was basically a 4-bit computer pretending to be a 16 bit one. (Skimming the tech manual it seems like it’s actually very similar to the Wang 2200 in some respects... and very different in others. Like not having that crazy BASIC-in-Microcode thing…)
 

Al Kossow

Documentation Wizard
Joined
Sep 1, 2006
Messages
3,455
Location
Silicon Valley
Believe me, I've looked for those. Virtually unobtainium today. But a great IC. On the other hand, someone has the TRW 16x16 multiplier in stock--only $300. Yet the AMD version is only $35 on eBay.

I wonder if the Moto MC10800 ECL ALU is any easier to find. I suspect not.

CMOS 16 or 32 bit versions of the 2901 architecture (alu, mux and dual-port ram) can be found and they're fast.
that still just gets you a data path, you still need the whole instruction decode microstore and timing logic to build the basic guts of a stored program CPU
and when you're done it isn't as fast or capable as what's in a modern FPGA. Its saving grace is visibility, though you can even get that if you implement a
scan chain in your fpga design.
 

Chuck(G)

25k Member
Joined
Jan 11, 2007
Messages
43,978
Location
Pacific Northwest, USA
Never said that it wasn't, Al. I suspect we're fast approaching the time when 90% of new logic is programmable, be it MCU, PSoC, FPGA or whatnot. Throw in a few discretes and you're done.
 

MattisLind

Veteran Member
Joined
Sep 30, 2013
Messages
1,153
Location
Stockholm, Sweden
The 8X300 was not bit-slice--just a bipolar early microcontroller. Mostly used in hard disk controllers, but you could find it scattered here and there. There was also a companion floppy controller chip and various other "extension" chips. Being bipolar, it runs hot as a pistol. You can pick it out from 10 feet on a board--there's always a series-pass regulator transistor nearby.
Never ment to imply that it was a bitslice. I know that it is a full bipolar microprocessor. The thougt-chain was going into Signetics/bipolar and then I got curious if the 8x305 was a Signetics only product or if it too was originally designed by SMS. But google sorted that out. CPUschack tell that the 8x305 was an Signetics enhancement. In my opinion it was easier to spot an 8x30x by its odd size. I know of no other chip in that form factor. 50 pin, 900? mil wide.
 

yuhong

Experienced Member
Joined
Mar 2, 2010
Messages
359
A typical board, one example off the top of my head, averaging the diffence across a large number of gate and flip flop & counter types, with about 65 74 series TTL IC's (Atari's arcade Pong) draws just over 1 Amp from its 5V supply. If you populate that same board with all 74LS TTL's instead, the current consumption drops to around 0.32A.
Which reminds me of projects like the TV Typewriter. It probably helped that acoustic couplers were legal thanks to Hush-a-Phone and Carterfone.
 

Chuck(G)

25k Member
Joined
Jan 11, 2007
Messages
43,978
Location
Pacific Northwest, USA
Yeah, the thing has what, 7 or 8 instructions? The whole family is interesting. Want subroutines? You need to get the interrupt controller (8x310), which implements 3 interrupts and a stack, using MOVE instructions that would normally be no-ops. Back in the day, it was pretty much the standard alternative to lots of SSI/MSI TTL.
 

Svenska

Veteran Member
Joined
Mar 19, 2007
Messages
722
Location
Sweden
I once thought about building a design using four 74'181 and one 74'182 (to save the carry chain), but when I tried to get the chips they exceeded my pocket money - so I never started.
 
Top