Need your Help: How to upgrade to 4M ram?

[OrBit]

Hi Gentlemen:

I have a Quadtel 386dx-25 PC. Its memory expansion board has a total of 640K system memory + 1024k extended memory. Recently, I want to upgrade it to total 4M memory. For this reason, I am purchasing an internal chip: hy53c464ls-80, 36 pcs in total, 2304k in total, When I install all of them, I find that they do not work normally. The system still shows that there is only 1024k extended memory.

I hope someone here can guide this matter. What type of chip can I purchase to make it work normally?

Thank you very much!

Henry

[cuttingedgecs]

What happens when you run setup? It seems odd that it's found a size mismatch between installed RAM and the value stored in the BIOS, but then setup can't update the stored value.

[OrBit]

In the BIOS, I changed extend memory to 2048Kb, when restart once again, the memory still show 1024kb and report this error message.

[mtx500]

That socketed chip with the white sticker 0011002035 could well be a PAL (Programmable Array Logic) or GAL (Generic Array Logic), that does the memory address decoding. Its programming could be specific for the memory configuration of that board, i.e. the number of chips and their sizes.
In that case, you would either need another board which has the same memory configuration that you are trying to achive, so you could read out the programming (if the security fuse hasn't been programmed) or try out the behaviour, or you have to reverse engineer where the lines from that PAL/GAL go to, i.e. what that chip controls. After that, you have to program another one (PAL) or re-program the existing one (GAL). Not easy.

I had that situation on my Memotech MTX500 homecomputer's memory expansion card that I upgraded from 32 KB to 512 KB. But that card was much smaller and easier to reverse engineer.

[cuttingedgecs]

[OrBit]

2 rows or 4 rows are all not available.

[OrBit]

Thanks for you information! base on my know crack PAL/GAL very difficult.

Any sugesstion will be apreciate.

Henry

[debs3759]

hy53c464ls id 64k x 4-bit, which is 32 KB, so 36 of them should be 1024 KB plus parity. If you have 1 MB on board, that would also explain why you only have 1 MB extended.