VOGONS

Interesting tidbits on 32 bit with parity Kingston memory expansion KTC-4000/KTC-1000 for compaq deskpro 386e.

Topic actions

First post, by pentiumspeed

Posted on 
User metadata
Rank l33t
Rank
l33t

I'm working on a project using a 4MB 72pin SIMM wired into kingston KTC-x000 (4MB or 1MB) memory expansion card as 1MB x 1bit DIP ICs is impossible to find at any price in quantity.

Layout of wiring of this memory expansion card conforms to 72 pin signal design! for 4MB, two RAS used (to tie together 2 banks of 8 bits plus parity bit).

Yet the four CAS lines are for 9 bit each bank which is 8 bit plus parity each at a time for total of four CAS lines needed to make 32 bits plus 4 parity bits for 386DX.

Yet the all the address lines are all tied together for all.

What is the reason to separate out four CAS lines while RAS lines are two for up to 4MB layout?

Cheers,

Great Northern aka Canada.

Reply 1 of 2, by Tiido

Posted on 
User metadata
Rank l33t
Rank
l33t

CAS are byte specific to accomodate byte writes from CPU etc. (and to lesser extent reads, but with reads the CPU can ignore unneeded bytes while it cannot with writes). Two RAS only exist for single/double sided conf aspect.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 2 of 2, by pentiumspeed

Posted on 
User metadata
Rank l33t
Rank
l33t

The full RAS 4 lines are used for 16MB and 32MB, no details how 8MB (two 4MB banks on one stick) sticks works.

I think the tied RAS to read out 16 bits at a time is due to 286 based chipset based on 24bits limitation and ISA DMA transfer compatibility?

Cheers,

Great Northern aka Canada.

Go to top of page Go to top of page
Back to General Old Hardware
Close window
Close window