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8087 on 8088 motherboard that have no socket for it

soviet9922

soviet9922

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Hi! i have taken a look at my Tandy HX and there no 8087 socket but after reading the tech manual of the 8087 and taking a look at the data sheet of both chips all the pins are almost identical it seem you can solder the 8087 on top off the 8088 and should work?.:confused:

comparison


System configuration


8087 data sheet
http://archive.pcjs.org/pubs/pc/datasheets/8087-FPU.pdf


This is useful


Fig. 8.15 Interfacing 8087 with 8086 / 8088

8087 can be connected to 8086 / 8088 only in their maximum mode of operation. In the maximum mode, all the control signals are derived using a separate chip called as a bus controller. The 8288 is a bus controller compatible with 8086 / 8088. The BUSY pin of 8087 is connected to the TEST pin of the CPU. The QS0 and QS1 lines may be directly connected to the corresponding pins in the case of 8086 /8088 based systems.

The clock pin of 8087 is connected to clock input of CPU. The interrupt output of 8087 is connected to the CPU through a Programmable Interrupt Controller 8259. The pins AD0 – AD15, BHE / S7, RESET, A19 / S6 – A16 / S3 of 8087 are connected to corresponding pins of the CPU.
 
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What are you planning to do with the 8087? Unless you plan on running very large spreadsheets, it won't provide much benefit.

The daughtercards designed to plug both an 8087 and 8088 into the 8088 socket on a PC Junior were very simple. Try searching for TIAC Manufacturing and see if you can find a picture of one to help guide the process. I prefer the side by side daughtercard layout. These chips can get warm and stacking them will definitely inhibit cooling.

It does look like stacking can work but I am probably overlooking a small detail somewhere.
 
I'm just in a neverending quest to max out my tandy HX, as you know the hx don't have any standard expansion. Replaced the cpu by a NEC V20 and a bunch of other stuff. Also add the 8087 seem very simple so why not do it?.
Yes you are right doing a side to side layout will be best because i plan to do some overclocking. What i don't see why this was not done before.
 
Ok seem that this pins are wired like the 8086 in this presentation shows how is done.
Test goes to Busy no rewiring.
PIN 30 on 8088 to 33 on 8087


From here
<div style="width:800px"> <strong style="display:block;margin:12px 0 4px"><a href="http://slideplayer.com/slide/2497875/" title="M ATH C O -P ROCESSOR 8087 Gursharan Singh Tatla 20-Nov-10 1" target="_blank">M ATH C O -P ROCESSOR 8087 Gursharan Singh Tatla 20-Nov-10 1</a></strong><iframe src="http://player.slideplayer.com/9/2497875/" width="800" height="649" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" style="border:1px solid #CCC;border-width:1px 1px 0" allowfullscreen></iframe><div style="padding:5px 0 12px"></div></div>
 
It's logical if you think about it. For example, BHE (bus high enable) doesn't exist on the 8088 because it has only an 8-bit external bus. MN/MX on the 8087 doesn't exist because the 8087 doesn't care whether or not an 8288 is present or not. RD doesn't matter because the 8087 uses the 8088 to do memory access...and so on.
 
soviet9922 said:
This are the only pictures i can find of the original module intel released when the 8087 was new to upgrade previous systems.

Click to expand...

I recall that module. Also I think there were some cad drawing of this or a similar module around. Will need to do some thinking on where.

Know I have some ceramic 8087's about, so circuit docs may be with them.

I know the MSDOS option pcb for the Otrona Attache, had an 8086 with empty socket for the 8087. There were detailed circuit drawings available for this board.
So maybe you can google this board and look at how Otrona did it. I did have these cct drawing, and feel I still have them. I know you are asking re 8088 NOT 8086 but any clues to connecting 8087 to an intel processor would be of value to you.

In fact I have a feeling I may still have one stored away in one of the 100+ crates of gear.
However I am unlikely to get to look in those crates for a few months yet.

There is also this book on ebay that may just help. I dont have hard copy to look at, to see what circuit info may be in it.
The Intel Microprocessors 8086/8088, 80186/80188, 80286, 80386, 80486,
Table of contents are

1. Introduction to the Microprocessor and Computer. 2. The Microprocessor and Its Architecture. 3. Addressing Modes. 4. Data Movement Instructions. 5. Arithmetic and Logic Instructions. 6. Program Control Instructions. 7. Programming the Microprocessor. 8. Using Assembly Language with C/C++. 9. 8086/8088 Hardware Specifications. 10. Memory Interface. 11. Basic I/O Interface. 12. Interrupts. 13. Direct Memory Access and DMA-Controlled I/O. 14. The Arithmetic Coprocessor and MMX Technology. 15. Bus Interface. 16. The 80186, 80188, and 80286 Microprocessors. 17. The 80386 and 80468 Microprocessors. 18. The Pentium and Pentium Pro Microprocessors. 19. The Pentium II Microprocessor. Appendix A: The Assembler, Disk Operating System, Basic I/O System, Mouse, and DPMI Memory Manager. Appendix B: Instruction Set Summary. Appendix C: Flag-Bit Changes. Appendix D: Answers to Selected Even-Numbered Questions and Problems. Index.


http://www.ebay.com/itm/The-Intel-M...995133?hash=item3d1f87bf7d:g:1JQAAOSwGXtXhbt7


BUT certainly the VERY best book you can get hold of is the INTEL produced "Intel iAPX 86,88 User’s Manual 1981 CPU Processor 8089 8086 8088". Look at this ebay listing.

you have choice of getting a soft copy at bitsavers

http://bitsavers.trailing-edge.com/pdf/intel/_dataBooks/1981_iAPX_86_88_Users_Manual.pdf see P682 on that covers the 8087

or buying a hard copy via ebay.

http://www.ebay.com/itm/Intel-iAPX-...005921?hash=item542c54c561:g:fdYAAOSwMORW70q7

Considering the number of pages and wealth of info my preference is look at soft copy and if more that 20% of book is worth printing out then just buy a hard copy as its way easier to thumb through or use as a quick reference.

Sorry that's the best I can do for you right now
 
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I'd be interested in running a clone board if anyone can find the schematic.
 
soviet9922 said:
This are the only pictures i can find of the original module intel released when the 8087 was new to upgrade previous systems.

Click to expand...

well I looked at the pic and did a google on the intel part number from pcb being PWA 142696.

I got a hit of a Russian, I think, saying he has "INTEL CIRCUIT BOARD PWA 142696 REV
Gold ic 13340048
I HAVE SEVERAL OF THESE BOARDS AND MANY OTHER RELATED IC CHIPS AND BOARDS SO CHECK MY OTHER AUCTIONS"

its in the text at right had lower at the following web address http://buynowus.com/ebay/list/item?obj[ItemID]=391008831085/

Maybe some else on here can better read that listing and ask him if he still has any. IF so I would really be interested in one.
 
iSBC 337 Multimodule NDP board for intel 8087

iSBC 337 Multimodule NDP board for intel 8087

Have a look at this link

seems the pic of the intel coprocessor board PWA 142969 leads to this doc. sadly its a text doc and no pics. MAYBE someone has hard copy or a PDF of it

https://archive.org/stream/bitsaver...SBC_337_Numeric_Data_Processor_Nov80_djvu.txt


I see the following mentioned in the text

1-2. DESCRIPTION

The iSBC 337 Multimodule NDP board (figure 1-1) is
based on the 8087 Numeric Data Processor. The 8087
provides powerful arithmetic operations on seven
different data types including single and double
precision floating point numbers, words, short and
long int^ers, BCD format, and internal file precision.



The co-processor interface of the 8087 to the 8086/
8088 CPU allows concurrent operation of the two
processors firom a single inclusion of the 8087 on
single board computers via the iSBC 337 Multi-
module NDP board, which is simply a plug on
option. The iSBC 337 MNDP board can also be
utilized by other 8086/8088 based designs, due to the
unique characteristics of the co-processor and Multi-
module interface.



1-3. EQUIPMENT SUPPLIED

The following is suppHed with the iSBC 337 Multi-
module NDP Board.

Schematic Diagram, dwg. no. 142698.

Figure 5-2. iSBC 337™ Board Schematic Diagram (sheet 1 of 1)

here is the pdf link below.. [ Edited to comment ""actually see my next post with further info""]

http://www.nj7p.org/Manuals/PDFs/Intel/142887-001.pdf
 
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soviet9922 said:
This are the only pictures i can find of the original module intel released when the 8087 was new to upgrade previous systems.

Click to expand...

99% certain this is the above pictured module layout, circuit and document in the pdf per link below
0I36v3T.jpg

iXDw1q0.jpg


and manual http://www.nj7p.org/Manuals/PDFs/Intel/142887-001.pdf

enjoy and hope someone can easily do a circuit board of same.

Guess there can be two board options depending on which side of processor, one can fit the 8087 onto, depending on the machine one wishes to add the 8987 co-processor to.

3rd option is a stacking arrangement. Seems most pins are 1 to 1 connection except on 8087 pins 31 goes to pin 30 on the processor and 8087 pin 33 goes to a connector P2-2 called RQ/GR1A what ever that is.

anyways I think I have done enough for now, so off to bed for me.
 
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I'm trying to remember what magazine it was, my google-fu is failing me... but aren't they so pin-to-pin that you can just piggy back them and only wire one pin different? Could have sworn I had a XT clone that actually came that way with the two literally soldered one atop the other.

-- edit -- actually, @inotarobot's post the circuit diagram shows that whilst there are more than one pin, that's basically all we're talking. That should be all the information you'd need to make a board for it.

Half tempted to try that with my Jr, but my Parkinsons is too far along for me to try that, as my attempt at a 512k conversion to a 128k board is proving.
 
Thank you very much, this information is great and also that shematic confirm that is just a wire job to get this working.
Have to purchase a pair of 8087 on ebay to do some testing now.
 
This reminds me of floating point exceptions. At least with the original PC it was a fairly simple connection using NMI. Unfortunately the PCjr uses the same NMI for the keyboard.
 
Awakening this old thread yet again.
Seems to me that the trickiest thing about adding an 8087 where there is no socket for it, is that you need to know (1) how to connect the INT output from 8087 ultimately to the NMI input of the 8088. If you don't have a valid schematic (or have a sense of the way it works) then ... thats a problem.
Also, doesn't either BIOS or DOS have to properly handle this NMI input as well?

More research needed.... ;)
 
Twospruces said:
Awakening this old thread yet again.
Seems to me that the trickiest thing about adding an 8087 where there is no socket for it, is that you need to know (1) how to connect the INT output from 8087 ultimately to the NMI input of the 8088. If you don't have a valid schematic (or have a sense of the way it works) then ... thats a problem.
Also, doesn't either BIOS or DOS have to properly handle this NMI input as well?

More research needed.... ;)
Click to expand...

The connection is well documented so adding a board should be relatively easy.

DOS and BIOS don't do anything to handle the NMI. Careless 8087 programming is an excellent method of locking a system.
 
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