MaTi wrote on 2020-10-12, 15:18:
Hi all,
Can someone advise me on which brand/model this board is?
Id like to see if I can find a manual..
Take a look on that sticker 😉
It's a Hedaka HED-988
Here are the jumper settings:
http://www.uncreativelabs.de/th99/m/E-H/31353.htm
And/or, alternatively, I have some questions on things Id like to do:
1) The battery has leaked.. I will replace it. However, next to the battery I see four pins. Are these indeed for an external batttery?
Alternatively I can solder it onto the current place of the battery
JP5 is for an external battery.
Note that the external battery connector does NOT charge the battery, but the onboard battery is charged. So make sure you connect the right type (rechargeable vs non-rechargeable) in the right place.
2) Can someone please educate me on those two rows of pins at the top? What are those?
Those are SIPP slots, for SIPP memory modules. SIPPs are electrically identical to 30p SIMMs, and you can indeed make one from the other by adding or removing pins.
3) Below that there are chips and some empty sockets. Is that the RAM for a 286? Can I upgrade the amount by buying anything for the remaining 8 sockets?
What should I buy? Right now the pc mentions 2MB ram on boot.
The extra sockets are smaller than the regular ones and are for parity (which is now not installed/enabled). You currently have 16 1Mb chips, which is the max you can install onboard. According to the TH'99 entry you can only get more (4MB) by removing the DIP RAM and installing 4 1MB SIPPs.
4) Below that there is an empty socket. What could that be for? Any ideas?
80287(XL) co-processor.
By the way, take a look at your processor - Harris 25MHz. This is the ultimate 286 motherboard with the fastest 286 CPU on it. I'd start looking for 4x 1MB SIPP for it 😉
Might be a challenge to find a co-processor that would work in here, although I heard rumours that some fast boards could run them async at ISA bus speed, in which case any 287 or 287XL rated for 10MHz would work.
Just checked those jumper settings and you can do OSC/1 and OSC/3. With the latter you'd be running the co-pro at 8.33MHz, nicely in spec for the 10MHz versions. Or you can add a second oscillator at OSC1 and let it run at exactly 10MHz - or 12.5MHz if using 287XL
Note that SimCity, ancient versions of AutoCAD and Lotus 123 are about the only applications that would actually use the co-processor, so it's hardly a must-have upgrade.