Recent content by HoJoPo

Jameco has 41256 DRAM chips in stock, from the schematic above it looks like the existing chips are 4164s, so swapping to 41256 for a 4x capacity upgrade makes sense.

Is it the Quickie by Vitesse? I used one in high school (1989 to 1991) on an Apple IIgs with Publish It! to add black and white photos for the photocopied school newspaper.

The RM 850 has a smart fan and won't turn on until the power supply is hot or under enough load (in excess of 300W).

On my HP Z 400 motherboard, the extra pin is a sense pin used to detect when a high TDP capable heatsink/fan combo is used, by grounding the fifth pin. This might be your pinout for that motherboard: https://pinoutguide.com/Motherboard/HP_Server_5_pin_Fan_conne_pinout.shtml

A couple of Mac Quadra towers and an SGI Crimson, if I remember right.

As Harry Anderson was a big mac user, I'd imagine it's some kind of macintosh conversion? https://en.wikipedia.org/wiki/Macintosh_conversion

I agree that the Keystone 8812 nylon standoff (.75 inch tall) looks to match the construction, size and dimensions of the original. Mouser and Digikey both have them in stock for about 30 cents each. They drop to 12 cents each if you buy a 1000...

I've considered using one of the CGA/MDA/EGA to HDMI adapters and a 9 inch 4:3 LCD panel so I'd have color EGA graphics in my Portable II. I have the EGA card and it does work very well with the stock monitor, and my stock monitor is in good condition, so this is a back burner project. I do...

To be accurate to the original, there are no rivets. That's just solder in the rivet holes, no rivets are present.

I think you can get the extra address lines by ORing (RAS2 or RAS4) for one, (RAS3 or RAS4) for the other. But I'm not sure if there is a timing issue...

To use 1 meg SIMMs you'd have to OR the three RAS signals into one RAS signal and do some logic to translate those RAS signals into the extra address lines you'd need, if I'm thinking right. Since write enable is tied together for all three banks at the motherboard, no need to do logic there.

I've re-installed the memory card, 2176k is working fine after running the setup program. No need to change the jumper. I have the Compaq EGA card in this as well, along with a 1GB Sandisk CF card acting as a type 42 528MB IDE hard drive in an adapter (card slot type so I can change the...

The stand offs have two spring tabs that hold them tight to the motherboard on the side with the memory card. With that spring taken into account, the stand off is about 2cm from the shoulder that holds the memory card above the motherboard. Edit: Added picture, this one has one broken of...

Can't measure with the board attached unless I remove the mainboard from my system, which I'm not going to do. From the surface of the board to the shoulder of the connector is... 1cm (at the C69 end). From the shoulder to the top lip of the connector is... 1cm. So, 2 cm overall height. The...

I think Jameco in the US has new NEC D41256-08 (80ns) in stock. https://www.jameco.com/z/D41256-08-NEC-Corporation-IC-41256A-08-DRAM-256K-Bit-256Kx1-80ns_2287695.html