Odd duck of the day: 74AS888 8-bit slicer

[stamasd]

I've just received this in the mail. Haven't even taken it out of the bag and foam it came in.

https://www.dropbox.com/s/jph0z2vjvw75mgb/1.jpg?dl=0

https://www.dropbox.com/s/lmg6cjd2sbirdvl/2.jpg?dl=0

I've seen them traded a few times on this board, but not too frequently. The last time was several years ago. I got them from another source.

I like odd duck chips, and this is in my opinion a good example of that. There is detailed information about the chip in TI's 1986 LSI data book, but then it completely disappeared from TI's literature. There must have been some uses for it, as this particular chip was supposedly pulled from a socket in a board that used it, but I cannot find any information about any systems that used it.

So what is it? Well nominally it's an 8bit BSP. Together with its companion chip the 74AS890 which is a microprogram sequencer they form a system and can be used to build processors in 8-bit increments. There';s also the 74AS887 which is the same as the 888 just without the cascading circuitry so it's not a bit-slice but rather a simple 8bit processor, and the 74AS895 which has different connections for some internal registers and is labeled in the datasheet as a "memory address generator".

But the interesting part is not written in the datasheet - it can be inferred by reading between the lines. What was the purpose of TI releasing this BSP in a time when BSPs were seriously on the decline? Take the AM2900 series which was released over 10 years before. It had a nice market share, but at the time that market was not growing, and was in fact starting to decline. The 1986 TI data book goes into great detail with articles on how to build a 74AS888/890 system that will emulate the AM2900 series.

I haven't found any stories about this processor and how it came to be made, but I think what happened is: several years before its release, someone at TI must have looked at the growing (at the time) market for AM2900 systems, and decided they wanted a share of that. They started designing this BSP in a way that it could emulate AMD's BSP in a way that they wouldn't infringe (the emulation/translation layer is all done with external components). It probably took them a while until the 888/890 were ready to sell, and by that time the market for BSPs had decreased to a point where no (or very few) new designs were made for it, and the existing ones were amply supplied by AMD and its licensees. Thus leading to the failure of this chip in the marketplace, and its sudden disappearance from TI literature. I may be wrong as I have no actual information and it's all based on deduction.

If you have actual information about this chip, its history and/or actual uses I'd appreciate if you could post it.

There's the TI 1986 LSI databook at bitsavers:
https://archive.org/details/bitsavers_tidataBookBook_38362177

[berni]

Thse chips appear already in the 1983 ALS/AS Logic Circuits Data Book.
This data book is also available at bitsavers. Look into chapter 4...

Berni