VOGONS


First post, by claesbas

User metadata
Rank Newbie
Rank
Newbie

I bough a pair of new 64mb https://www.ebay.com/itm/131808663007?euid=nu … 1&sojTags=bu=bu here - just out of curiosity if they could run in my Unisys 486 DX4 100mhz machine.

I installed them and they do boot up the machine. They are found as 16mb though. So if I put both in I get a total of 32mb - and if I add my old 4mb also I get a total of 36mb (for some reason).

Is there any BIOS or other settings that I could try out to make my system see them as 32mb or even 64mb?

I am pretty happy with 32mb ram (was 8mb before) but would be interesting to push that up to 64 or even 128.

Reply 1 of 11, by dionb

User metadata
Rank l33t++
Rank
l33t++

That eBay auction is very fishy... the image shows SIMMs with KM44C1000BJ-6 chips. Those are 1Mx4 4Mb chips. A SIMM with 16 of those chips is only 8MB, not 64MB as claimed. For 64MB you'd generally use 8 16Mx4 (64Mb) chips, or alternately 16 8Mx4 (32Mb) chips.

I strongly doubt you actually got 64MB SIMMs, and the 16MB you did get doesn't correspond with the picture either 😦

Could you perhaps post the exact code on the individual chips on the SIMMs you have (no pics needed, just text should be fiune).

Another possibility is that they are actually 64MB SIMMs using 64Mb chips, but your motherboard chipset (which you don't mention...) only supports max 16Mb chip density, in which case you'd expect the SIMMs to get detected as 1/4 of their nominal size, i.e. the 16MB you are seeing. But first let's figure out if you have actually received what you paid for. If that does check out, we need to look at your chipset. Could you perhaps post which you have?

Reply 2 of 11, by claesbas

User metadata
Rank Newbie
Rank
Newbie

Thanks for the reply.

So on the chips it says: SEC KOREA 913 KM44V16100CS-6

and on the sticker it says: PNY 69000176 253-20064-60

Image:

64simm2.jpg
Filename
64simm2.jpg
File size
1.08 MiB
Views
1116 views
File license
Fair use/fair dealing exception

And my Chipset is (Via or Sis) I am not sure:

chipset.jpg
Filename
chipset.jpg
File size
1.78 MiB
Views
1116 views
File license
Fair use/fair dealing exception

Reply 3 of 11, by claesbas

User metadata
Rank Newbie
Rank
Newbie

Some images of boot + bios settings:

Attachments

  • 20190424_122605.jpg
    Filename
    20190424_122605.jpg
    File size
    445.01 KiB
    Views
    1106 views
    File license
    Fair use/fair dealing exception
  • 20190424_122554.jpg
    Filename
    20190424_122554.jpg
    File size
    447.83 KiB
    Views
    1106 views
    File license
    Fair use/fair dealing exception
  • 20190424_122537.jpg
    Filename
    20190424_122537.jpg
    File size
    431.51 KiB
    Views
    1106 views
    File license
    Fair use/fair dealing exception
  • 20190424_122520.jpg
    Filename
    20190424_122520.jpg
    File size
    511.1 KiB
    Views
    1106 views
    File license
    Fair use/fair dealing exception
  • 20190424_122446.jpg
    Filename
    20190424_122446.jpg
    File size
    200.42 KiB
    Views
    1106 views
    File license
    Fair use/fair dealing exception

Reply 4 of 11, by dionb

User metadata
Rank l33t++
Rank
l33t++
claesbas wrote:
Thanks for the reply. […]
Show full quote

Thanks for the reply.

So on the chips it says: SEC KOREA 913 KM44V16100CS-6

and on the sticker it says: PNY 69000176 253-20064-60

Image:

64simm2.jpg

Fortunately a totally different SIMM to the eBay images. Lazy/lousy seller, but at least not trying to sell 4/8MB SIMMs as 64MB.

KM44V16100CS-6 is a 16Mx4 chip, i.e. 64Mb, and eight of those make 64MB (or nine in this case as it's a parity module). So the SIMM checks out: single-sided (as 32/36 address lines, regardless of where the chips are physically located) 64MB parity SIMM.

Interestingly - but not relevant here - the chips are 3.3V and the SIMM has an onboard voltage regulator (that MOSFET) to drop from 5V SIMM voltage to 3.3V chip voltage.

And my Chipset is (Via or Sis) I am not sure:

chipset.jpg

Why not sure, it's right up there in your pic, SiS 471. Which is rather old and almost certainly why you're not getting the full 64MB out of these SIMMS.

Here's the datasheet:
ftp://retronn.de/docs/chipset/SiS%20471.pdf

Fast Page Burst Mode DRAM Controller-4 Banks up to 128MB of DRAMs-256K/512K/1M/2M/4M/16MxN DRAM Type

There's your problem. Just to confuse you, the "M" here is almost competely unrelated to the "M" in chip density. This simply refers to the number of MB per bank. A single-sided SIMM is one bank, a double-sided SIMM fits two banks. Max for one bank is 16MB, and that's what your 64MB SIMMs are showing up as. What this actually means is that the SIS 471 can handle a max of 16Mb chip density. To get 128MB on this board, you'd need four 32MB dual-sided (64/72 address lines) SIMMs.

Reply 5 of 11, by claesbas

User metadata
Rank Newbie
Rank
Newbie

Thanks sooo much for this explanation. I didn't know about the single/double sided thing before. I am pretty happy with 32mb ram in this machine to begine with. Maybe I add another paid of 16 to push it to 64mb in the future.

Reply 6 of 11, by dionb

User metadata
Rank l33t++
Rank
l33t++

This isn't a single/double sided thing but a memory density thing. This chipset won't recognise chips over 16Mb. A consequence of that is that to reach the amount of memory you want you have to do it with a different type of (double-sided) memory, but that's effect, not cause.

By the way, you might not even want to add that much memory to the system with your current cache configuration. I can't see exactly what cache chips you're using on the motherboard pic but one screenshot shows 256kB. Check pages 7 and 8 of the SiS 471 datasheet. The amount of RAM the motherboard can cache depends in the amount of cache present and the tag configuration. You have 256kB cache, which means either 32MB (7b tag) or 64MB (8b tag) is cachable. Rule of thumb to determine 7b vs 8b: count the cache chips. If you have an odd number (power of two plus one, i.e. 4+1=5 or 8+1=9), it's 7 bit and the lower limit applies, if it's an even number (power of two plus two, i.e. 4+2=6 or 8+2=10) it's 8 bit and the higher limit applies. Either way, your board can't cache over 64MB and maybe not over 32MB. Uncached RAM access is slower, so unless you are actually using all that RAM (highly unlikely on a 486 desktop) going over that limit will make it run slower than it does now with 32MB.

You could use the uncached RAM as a RAMdrive (because even uncached RAM is much faster than any disk access), but getting that setup is non-trivial.

Reply 7 of 11, by manuelink64

User metadata
Rank Newbie
Rank
Newbie

I have a similar PC (same brand), the max amount of ram allowed, 4 stick of "16MB 4Mx36 FPM MEMORY PARITY 60NS SIMM 72-PIN 5V"
for a total of 64MB of ram!. Win95 and my AMDx5-133 runs very well (I changed the Intel DX4 100)

check this seller on ebay
https://www.ebay.com/itm/16MB-4Mx36-FPM-MEMOR … 8EAAOSwP2pa~dqI

Regards!

[Unisys CWP] [CPU] AMD-X5-133ADZ [RAM] 64 MB (4x36) FPM [HDD] Seagate 8.4GB [Audio] SB16 SCSI 2 (CT1770) [Video] ATI Mach64VT2 [OS] Windows 95 OSR2.5

Reply 8 of 11, by claesbas

User metadata
Rank Newbie
Rank
Newbie
dionb wrote:

This isn't a single/double sided thing but a memory density thing. This chipset won't recognise chips over 16Mb. A consequence of that is that to reach the amount of memory you want you have to do it with a different type of (double-sided) memory, but that's effect, not cause.

By the way, you might not even want to add that much memory to the system with your current cache configuration. I can't see exactly what cache chips you're using on the motherboard pic but one screenshot shows 256kB. Check pages 7 and 8 of the SiS 471 datasheet. The amount of RAM the motherboard can cache depends in the amount of cache present and the tag configuration. You have 256kB cache, which means either 32MB (7b tag) or 64MB (8b tag) is cachable. Rule of thumb to determine 7b vs 8b: count the cache chips. If you have an odd number (power of two plus one, i.e. 4+1=5 or 8+1=9), it's 7 bit and the lower limit applies, if it's an even number (power of two plus two, i.e. 4+2=6 or 8+2=10) it's 8 bit and the higher limit applies. Either way, your board can't cache over 64MB and maybe not over 32MB. Uncached RAM access is slower, so unless you are actually using all thatCa RAM (highly unlikely on a 486 desktop) going over that limit will make it run slower than it does now with 32MB.

You could use the uncached RAM as a RAMdrive (because even uncached RAM is much faster than any disk access), but getting that setup is non-trivial.

Can you see in this picture what cache I have?

cache2.jpg
Filename
cache2.jpg
File size
883.79 KiB
Views
1013 views
File license
Fair use/fair dealing exception

Reply 9 of 11, by dionb

User metadata
Rank l33t++
Rank
l33t++

The picture is much too blurry to make out the chips,but it looks like nine of them in any event, so I suspect 7 bit. That means max 32MB cacheable with 256kB cache like you have.

Reply 11 of 11, by bjwil1991

User metadata
Rank l33t
Rank
l33t

Sometimes, the seller neglects to check and see what the size of the memory is, to be honest. My 486 has 32MB SIMM-72 installed and 4MB on-board, which is disabled at the moment since some games choke if there's more than 32MB RAM installed.

Discord: https://discord.gg/U5dJw7x
Systems from the Compaq Portable 1 to Ryzen 9 5950X
Twitch: https://twitch.tv/retropcuser