VOGONS


First post, by Omarkoman

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I bought this video card :

s-l1600.jpg

and also these memory chips : https://www.aliexpress.com/item/32833040925.html

so I can upgrade from 2MB to 4MB

I am hoping to get some guidance on orientation of the memory chips, how do I know which way I put them in?

Also, the card appears to have an audio output, googling it says its mpeg audio out, what does that mean? I remember in old days there were hardware mpeg decoder cards and this video card has headers as well perhaps for one of those. I take it the sound out is not usable without one?

thanks in advance!

Reply 1 of 6, by DerBaum

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the sockets have a notched corner (top left in the picture). thats pin 1.

the datasheet of your memory chips will tell you how they have marked pin 1 on the chip.
(From the pictures it looks like your chips (on the card and aliexpress) have a slightly diffenrent shaped edge where pin 1 is)

And then just push them in. Its a little firm but nothing will break.

FCKGW-RHQQ2

Reply 2 of 6, by Omarkoman

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awesome, thank you!

any thoughts on that audio output?

Reply 3 of 6, by Error 0x7CF

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Virge/trio cards support a daughterboard for mpeg-1 decoding. The headers on your board don't match what I know for the only one I know of, so I don't know what mpeg daughterboard you would need.
I've played with one of the daughterboards a bit, I was never able to tell on my P166 w/win95 whether it was working or not. I tried multiple cards between trio64 and virge and was never able to discern anything. It's probably not worth bothering with.
The board I have has two cd-audio connectors for audio output and audio input so it can take audio in from the CD drive and overlay its own on the way to your sound card, but since your board would probably be different, it might instead output through the back.

Last edited by Error 0x7CF on 2023-10-15, 01:18. Edited 1 time in total.

Old precedes antique.

Reply 4 of 6, by giantclam

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Do 25ns chips get along with 35ns timings?...I guess you'll find out =)

Reply 5 of 6, by Omarkoman

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If it was the other way around it would be an issue but should be ok if they are faster, they will just run at lower speed?

Reply 6 of 6, by mkarcher

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giantclam wrote on 2023-10-15, 01:15:

Do 25ns chips get along with 35ns timings?...I guess you'll find out =)

If the new chips you ordered are actual 25ns chips (and not relabelled 50ns chips), they should work fine.

In case you wonder about the 100MHz marking in them, whereas a period of 25ns would correspond to a frequency of 40MHz, this is because the "25ns" is the RAS access time, so it assumes the chip being in idle state (no bank open) and measures the time from the idle state to getting valid data from that chip. As long as you hit the optimal timing for dealing with the address multiplexing, the /RAS and the /CAS signals, you can get valid data 25ns after you started getting the chip out of "idle" mode (i.e. asserting /RAS). Because this measures the time that passed between asserting /RAS and the data access working, this is called "/RAS access time". At the end of the /RAS access time, the chip is not in idle state, but the bank needs to be closed before a new bank can be opened. The time from asserting /RAS for reading from bank to asserting /RAS again for reading another bank is higher than 25ns and is called the "/RAS cycle time", which on 25ns RAM is likely about 40ns.

On the other hand, the 100MHz marking on that chip indicates a suitable memory clock of the graphics card, if it operates in "singly cycle EDO mode". You Virge card most likely does (if it doesn't the 3D performance is even more atrocious as it generally is on the 86c325), and you are accessing different cells inside a single bank that is already active. The 10ns associated with 100MHz is the time from asserting /CAS for one read cycle until /CAS can be re-asserted for the next read cycle in the same bank. This timing is known as the "/CAS cycle time". 10ns /CAS cycle time is a standard timing for 25ns RAM. The 86c325 is officially specified for clocks around 50 to 55MHz, so it clearly won't use the full potiential of the 10ns /CAS cycle time, but in case you are interested in 3D applications, and you want to run applications at higher resolutions than 400x300, you might want to look into overclocking that chip. I found that given sufficiently fast RAM, 86c325 chips often work fine up to 80MHz, which will give them a severely needed speed boost if your favorite S3d game made the stupid choice to run at 640x480 (as Terminal Velocity did, most likely because their game assets are designed for 320 or 640 pixels horizontal). Which makes me wonder - how much fun could Terminal Velocity have been on a 486 computer, if it included a 320x240 hardware-assisted mode?