Regular readers will have gathered that I am an inveterate hoarder of all things electronic, and (as a subset of the above) a devoted scavenger of parts off old boards. Occasionally I come across Integrated Circuits on old boards for which I will have no possible use, but which are unusual enough in appearance that I will keep them and perhaps even disassemble them further, if that is possible. This is a short slideshow of some of the more unusual – and, I think, beautiful – ICs I have come across in my meanderings, which may bring happy memories to some readers who may have dealt with them (or even designed them) in the past, and smiles of disbelief to younger ones who have not had the privilege of working with these old through-hole components.
Take this monster. It consists of a square ceramic base nearly 3 inches on the side, with 3 separate big SMD ICs mounted on it, along with a few SMD capacitors and one resistor. So I guess technically it’s a hybrid circuit, not an IC per se , but it is pretty…. One of the ICs has a round heatsink mounted on it like a helipad. It came out of an old server. It has a paper label affixed to it proclaiming itself to be a CYM7232S40HGC, and the brief datasheet I found on the net for it tells me that it is a DRAM Accelerator module, with 64-bit data busses and 32-bit error correction. It apparently had a big brother, the CYM7264, which did 64-bit error correction. 371 pins (my count) and a huge socket came with it. The datasheet is dated 1995 and there is what might be a date code of 3993 (1993; week 39) on the label.
Of course many of the original through-hole Large-Scale Integration (LSI) ICs that came out were on ceramic carriers; you don’t see them much any more. A lot of the original microprocessors came with a ceramic option and the sight of one never fails to lift my heart, for some reason. I think ceramic packages were more temperature stable and used for parts specified for larger temperature ranges? Here is an old ULA (Uncommitted Logic Array) – the forerunner of todays FPGAs. I got a few of these and by judicious heating I managed to take the metal lid off one of them exposing the chip and connecting wires inside.
Standard 40-pin format, but a nice geometric looking chip inside and that lovely bonding strip across the top of the IC. My USB microsope is only 1.3 Megapixels, alas, but here’s what the chip looks like at that resolution:
Continue to the next page: That’s not an IC – THIS is an IC! >>
That’s not an IC – THIS is an IC!
Another monster – this is an HD68450, a DMA IC for Motorola’s 68000 series microcomputers, second sourced from Hitachi. 64 pins – 32 each side, and about 3.2 inches long. Another lovely old ceramic IC. I have included a couple of standard 74-series ICs in the photo for comparison – a 20 pin and a couple of 16-pin types.
This one is on a processor board from an old voicemail system, which also had a 68010 processor in a plastic DIP 64-pin package. Like the 68450, the width is about 0.9 inches – half as much again as a standard 40-pin chip:
Here you can compare it with the 28-pin Eprom above the ruler. These 64-pin chips were probably the biggest ICs produced before processors went to the Pin Grid Array packages we all know from the older PCs we may have used – anything from 286’s to 486’s and Pentiums, and the Ball Grid Arrays that are used for most big (and even some small) ICs today. But all of the peripheral ICs produced for the 68000 series are big – take this 48-pin 68901 – standard 0.6 inch width but a much longer IC than the standard 40-pin packages. It’s a multifunction peripheral, with I/O, interrupt control, timers and a USART. And all these ICs had the standard 0.1 inch pin spacing. Later ICs have reduced the spacing between the pins to get more pins in the same package size, but in the good old days 0.1 inch pin spacing was a sacred standard.
The same voicemail system also had two Seagate 50-pin SCSI hard drives of 2.5 GB each (“What’s SCSI? And what’s a Gigabyte, daddy?” I hear younger readers ask plaintively…) but that is getting off-topic, we’re here to talk about ICs.
Continue to the next page: Windows… not the PC type…..
Windows… not the PC type…..
Before the flash memory that all the microcontrollers use these days we had Eproms. (“What’s an Eprom, daddy?? :‑) The nice thing about them was that, as you had to expose them to UV light to erase them, they had a window through which you could see the actual chip. And not only did it let UV light through, it let visible light though to photograph them. And very pretty they could be too. If you got the light right you’d get all sorts of colours off them, I think from interference patterns due to the repetitive nature of the individual memory cells on the chip. The physical size of the chips seemed to get smaller as they got larger in capacity, but then bigger again as we got up to the 2-and 4-megabit chips. The biggest one below is in the middle of the range – the 27C512. (Am I the only one who found it annoying the way the numbers were the kbits, not the Kbytes? So a 27256 only held 256/8 = 32 Kbytes?) Anyway, here’s a few pics of Eprom chips:
Eprom Technology. Note the colours reflected by the chips when light strikes them. From left to right: a 2716 (2K Bytes); a 27256 (32K) a 27C512 (64K) a 27C4001 (512K) and an MC68HC705 – an early 6800 based microcontroller with CPU, Eprom, Ram, I/O and a timer. Some versions of microcontrollers were produced as “OTP” (One Time Programmable) versions – with the same Eprom but a sealed plastic carrier. Much less pretty, and you had to be sure you programmed them right – once they were programmed, that was it. Most Eproms were in a ceramic carrier – easier to interface with the glass window and less susceptible to temperature effects.
The sun sets on Eprom technology – a 27C4001 showing its not-so-true colours. Not many bigger Eproms than this were made – flash technology has now taken over and we’re back to boring old plastic ICs. Here’s a close-up of the same chip:
Continue to the next page: More Pins >>
One trick that manufacturers used to get more pins in a smaller area was to use Quad-in-line packages, with pins taking two lines of holes on each side of the chip. This let manufacturers put the leads closer together without needing smaller pads on the PCB. Here’s a large sized one:
This technique was even used on small ICs. The MFC6040 was a Motorola electronic attenuator IC with only 6 pins. I bought a few for a project yonks ago and still have a couple. It was way pre-internet, and when I looked a few years ago I couldn’t find a datasheet for it, but some kind soul has now posted one here (Thanks Jim). The pin spacing is 0.75 inches and between 0.3 and 0.6 inches wide. It provided 0 to 90 dB attenuation with a 50K pot (which could be remoted and could control several ICs) but the THD got up to 3% at high attenuations. I don’t think I’ll be using them anytime soon.
Of course before we had DIL ICs we had the round TO-99 packages for op-amps and even some old digital ICs. The early 709 and 741 opamps were very common in this package. They were called TO-99 when they had 8 or 10 pins (I have seen TO-74 used for 10-pin types) and TO-5 or TO-39 when they were just 3-lead transistors. It’s surprising what you can find in these old round packages – I even have some 555 timers in them. Here is an assortment of these ICs. This was the common package for early ICs of all types.
From Left – top – An MC1455 (Motorola’s 555); a TAA 300 1W audio Amp; an AD517 precision OpAmp; a CA3053 differential amp and a National LM565 PLL. Bottom: an MC1550 wideband amp; an SL630C VOGAD (AGC); a CA3085 voltage regulator; and LM709 and 741 OpAmps.
The venerable 723 Voltage Regulator IC was also made in this package. Here are two, including one where someone seemed to have designed a PCB the wrong way round and the IC was mounted inelegantly upside-down with its legs in the air.
Of course not all ICs are beautiful, even when they are right-side-up. Plessey in England and a couple of other manufacturers in the old days produced Audio Amplifier ICs that you could bolt a heatsink onto. Nowadays they look really ugly. Sinclair Radionics, a very go ahead company in England in the 1960’s and 70’s, contracted Plessey to produce one for them called the IC-10, supplied with a PCB. A friend of mine had one but in spite of the heatsink they were fairly finnicky things and it did not last long. Recently one of my suppliers offered a later type, the TAA621, with this type of heatsink in their clearance email. I’m tempted to get some for old times’ sake but… only 4W out and distortion not given, so probably around 2-3%….naaah…..
Here’s a pic of two of them….a TAA621 which had a quad-in-line pinout, and below that a top view of a Plessey SL403D with only 10 pins, which was very similar to the Sinclair IC-10. I think the TAA621 just has the heatsink glued to the top of a normal chip, whereas the SL403D actually encapsulates the heatsink and I think the chip is mounted directly on the metal. Which does not explain why they were so unreliable….
I have covered here a few of the more unusual ICs I have come across, but there are plenty more. Russia made some strange looking ones (Google Russian Integrated Circuits to see a few) and I’ve come across others which I have long since lost – a 10-pin TO-3 case (usually used for big transistors) voltage regulator comes to mind. What weird ICs have you dealt with? Let us know below (with photos or links if possible).