First post, by atari52oo
Hello!
I recently acquired a 386DX40 board that started to throw himem.sys errors after the machine was warmed up and running for a short while.
After the board has been running for roughly 10+ mins I start to get the following error from himem.sys when rebooting:
"HIMEM.SYS has detected unreliable XMS memory at address 002EB7FAh."
I switched out the simms and the error continued at the exact same memory address. The board has CPU cache memory (64KB currently), so I started to remove and swap around those chips. When I did so, I got the memory address of that error to move to different address. So my working assumption is that one of the cache SRAM chips are bad on this board.
Here is where I'm looking for some help since I'm super educated on individual RAM chip configurations.
I have the Micro House manual for this board, and it says that the board can be configured for 64KB or 256KB cache using either 8K x 8 chips, or 32K x 8 chips.
See this image of the capture of the page in the PDF manual: https://i.imgur.com/QYB84uU.jpg
- Note the manual says there are only 8 cache chips.
Here is a picture of the board's actual cache chips: https://i.imgur.com/ZXTlOYe.jpg
- Note there are actually 11 cache chips. 10 in dual DIP-22/24 sockets, and then one in a DIP-22 socket.
ALL 11 cache chips which are installed in my board are 16K x 4 (Micron 5c6404-15) chips.
So here is my confusion and questions:
1. I'm assuming the Mico House manual is wrong in this case on the type of cache chips?
2. Does my board actually only take 16k x 4 chips for it's 64KB cache configuration and not 8k x 8 as well?
3. If I wanted to upgrade this board to 256KB of cache (Because why not!) would I then use 64k x 4 chips?
4. I've drawn boxes around three groups of the cache chips in thinking that the first one with 8 in the dark blue are probably the 8 main cache chips? The two in the Green box are probably Tag chips? And the last in the light blue might be a dirty bit / write back cache chip? This single chips is the only one that not socketed in a dual dip-22/24 socket.
Thanks for reading and hopefully I can get some other's thoughts on this!
IBM PS/2 Model 70 (Type: 8570-121)
386DX-20 / 6mb ram
ZuluSCSI - SD card Storage
Slot1: MCS-600 SCSI
Slot2: 3Com 3c529-TP NIC
Slot3: Snark Barker MCA (SB Clone)