CPU Shack: Datatek 386 Motherboard with CPU/FPU - SOLD

[CPUShack]

Here is a nice Datatek motherboard.
Datatek ones are kinda cool as they did everything on their own, even their own branded BIOS

It included 4-30 pin RAM slots, and 1MB of RAM (5MB max) (implemented with Intel DRAMs no less)

Processor is an Intel NG80386SX-16 C STEP
FPU is a nice PLCC Cyrix CX-83S87-16-JP

$20 and its yours

[Elar]

There is no cache on this board. The board is DTK PPM-1630C:

http://www.arvutimuuseum.ee/th99/m/C-D/30050.htm

[CPUShack]

Haha the box was marked 64k woops

so thats 1MB with parity on the board, of RAM, super cool! + you can add SIMMs for 5MB total

[stamasd]

$20 and it's mine, if you confirm that the battery hasn't leaked. Can't really tell from the angle of the picture.

[CPUShack]

Just starting to, but not bad and nothing on the PCB

[stamasd]

OK then I'll take it.

[Chook]

A 386SX-16 with no cache. That would be slooooooooow!

[kixs]

386SX rarely had any cache.

I agree it will be slow. 286-16 would be faster.

[stamasd]

I know exactly how slow it is. This is not my first 386SX-16. The other one is a Magnavox 386 computer. The neat thing about the other one is that in theory the CPU is upgradable, as it's on a daughtercard (proprietary connector). In practice though finding a proper card to upgrade it with has proven a futile enterprise.

Closeup of the CPU card (not my picture, but mine is identical)

[CPUShack]

They do at least make the clip on upgrades for them

[stamasd]

[CPUShack]

must be rev D then

interesting the C steps are so marked

[stamasd]

Here it is from the mouth of the (dead) horse: The Cyrix 486D/SRx2 hardware compatibility.

Last paragraph says
"The Cx486SRx2 Upgrade processor is designed to work in any 386SX (20 and 25 MHz) computer that follows industry standard socket and BIOS designs. Due to a 386SX design change in 1991, the Cx486SRx2 will also work in 16 MHz 386SX PCs manufactured after 1991."

http://web.archive.org/web/19970616072959/www.cyrix.com/process/prodinfo/legacy/upover.htm

Wish I could test it. I have a few DRx2 chips, but no SRx2.
Just found this today; guess that would be the evidence I was talking about in my previous post.


(edit) the specific mechanism that allows the DRx2 to work is pin 28 on the 386SX package, which in CPUs made after 1991 is signal FLT#; when asserted, it puts the CPU buses in high-Z state, i.e the CPU becomes electrically isolated from the bus according to the datasheet from 1991 http://microblog.routed.net/wp-content/uploads/2006/05/386sx.pdf
(see pins description and page 60 "float")
The original datasheet of the initial revisions of the 386SX shows pin 28 as unused and makes no mention of the float mechanism, e.g. this one from 1988 https://ia801303.us.archive.org/20/items/bitsavers_intel80386ceInformationMay88_6752701/240187-001_386SX_Advance_Information_May88.pdf

[CPUShack]

C STEP came out in about 1991 wonder if that includes it then? (earliest I have in 9041)

[stamasd]

I don't know. Neither datasheet has info about silicon steppings.