VOGONS


Reply 20 of 32, by analog_programmer

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majestyk wrote on 2024-04-06, 08:16:

This referred to "tvsat" in Poland.

I see. The shop from the other link "allegro" needs profile registration for making a purchase and its prices are in PLN (zloty?) only and I can't understand if I can pay and how much it will cost in EUR. "Tvsat" shop seems OK.

What's going on here, could it be that the only active online vintage electronics stores with normal prices are located in Poland? 😀

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Reply 21 of 32, by analog_programmer

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rasz_pl wrote on 2024-04-06, 08:24:

all three links are to the same tvsat shop from Poland 😀

Aha, so this "allegro" is actually "tvsat", but with different prices. It looks like it would be least profitable to order chips from their ebay shop-account, but do they fulfill international shipments through "allegro" site? How much PLN is 1 EUR in Poland?

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Reply 22 of 32, by wierd_w

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Google says 1 euro = 4.28 zloty

Reply 23 of 32, by rasz_pl

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analog_programmer wrote on 2024-04-06, 08:45:
rasz_pl wrote on 2024-04-06, 08:24:

all three links are to the same tvsat shop from Poland 😀

Aha, so this "allegro" is actually "tvsat", but with different prices.

allegro is Polish ebay
cheapest will probably be straight from tvshop.pl link posted by majestyk

AT&T Globalyst/FIC 486-GAC-2 Cache Module reproduction
Zenith Data Systems (ZDS) ZBIOS 'MFM-300 Monitor' reverse engineering

Reply 24 of 32, by analog_programmer

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rasz_pl wrote on 2024-04-06, 09:05:

allegro is Polish ebay

I didn't knew that 😀

rasz_pl wrote on 2024-04-06, 09:05:

cheapest will probably be straight from tvshop.pl link posted by majestyk

If 1 euro = 4.28 zloty is the actual exchange rate, then the lowest prices are in "allegro", but still I have to make an account just to see if there is an option for international shipping and how much it will cost converted from zloty. I think at the end the order including shipping costs will not be much cheaper than their prices in "tvsat" which are in EUR. Their prices in USD in real ebay seems higher after conversion to EUR.

rasz_pl and majestyk, thanks for all the info for this Polish shop, guys!

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Reply 26 of 32, by analog_programmer

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Thank you for all the information, rasz_pl! I'll order ten 4M x 1 FP-RAM chips from shop.tvsat.com.pl, but now I'm in search for datasheets for unknown to me "A413256J06" chips used for VRAM on one old ISA UMC videocard (I want to double the size of its VRAM from 512 kB to maximum supported 1 MB). I'm planning to order as much as possible RAM chips in one parcel.

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Reply 27 of 32, by mkarcher

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analog_programmer wrote on 2024-04-06, 09:59:

Thank you for all the information, rasz_pl! I'll order ten 4M x 1 FP-RAM chips from shop.tvsat.com.pl, but now I'm in search for datasheets for unknown to me "A413256J06" chips used for VRAM on one old ISA UMC videocard (I want to double the size of its VRAM from 512 kB to maximum supported 1 MB). I'm planning to order as much as possible RAM chips in one parcel.

Some parts of the chip number "A413256J06" have a meaning obvious to experienced electronics engineers: "256" is either the amount of kilobits or the depth (i.e. the number of addresses). On a 512KB card, I expect 4 chips of 256K x 4. "J" is the package type SOJ. "06" is the access time: "60ns". The "3" in the type code feels kind of unusual, but might just be a vendor-specific indication of fast page mode support. If the chips are in a SOJ26/20 package (like the parity chips you need to complete the 4M modules), they are extremely likely to be standard 5V FPM 256K x 4 chips, commonly called 44256. Those were by far the most common memory chips used on entry-level 1MB SVGA cards around 1990-1994. The cross reference I posted should mention different vendor-specific chip type numbers for that kind of memory.

Reply 28 of 32, by analog_programmer

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mkarcher wrote on 2024-04-06, 11:53:

Some parts of the chip number "A413256J06" have a meaning obvious to experienced electronics engineers: "256" is either the amount of kilobits or the depth (i.e. the number of addresses). On a 512KB card, I expect 4 chips of 256K x 4. "J" is the package type SOJ. "06" is the access time: "60ns". The "3" in the type code feels kind of unusual, but might just be a vendor-specific indication of fast page mode support. If the chips are in a SOJ26/20 package (like the parity chips you need to complete the 4M modules), they are extremely likely to be standard 5V FPM 256K x 4 chips, commonly called 44256. Those were by far the most common memory chips used on entry-level 1MB SVGA cards around 1990-1994. The cross reference I posted should mention different vendor-specific chip type numbers for that kind of memory.

There are two "A413256J06" SOJ 26-pin chips soldered directly on the card's PCB paired with two socketed DIP-20 Samsung KM44C256AP-10 (256K x 4) for a total of 512 kB VRAM, so I think you're absolutely right about the chip's size, voltage and speed. I can add two more DIP-20 (in sockets) or SOJ26 chips soldered on the PCB.

This is the very same VGA card: https://www.vgamuseum.info/images/palcal/umc/ … 08af_top_hq.jpg (on this picture the socketed chips are missing)

There are memory configurations with six VRAM chips on the same videocard model: https://www.vgamuseum.info/index.php/cards/it … -umc-um85c408af

If there are no suitable 256 kB chips, I think I can upgrade this card to 768 kB VRAM adding two more 128 kB chips. I don't know if I can use two 1 M x 4 chips (for 1 MB VRAM) instead of current four 256 K x 4.

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Reply 29 of 32, by mkarcher

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analog_programmer wrote on 2024-04-06, 12:43:
There are two "A413256J06" SOJ 26-pin chips soldered directly on the card's PCB paired with two socketed DIP-20 Samsung KM44C256 […]
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mkarcher wrote on 2024-04-06, 11:53:

Some parts of the chip number "A413256J06" have a meaning obvious to experienced electronics engineers: "256" is either the amount of kilobits or the depth (i.e. the number of addresses). On a 512KB card, I expect 4 chips of 256K x 4. "J" is the package type SOJ. "06" is the access time: "60ns". The "3" in the type code feels kind of unusual, but might just be a vendor-specific indication of fast page mode support. If the chips are in a SOJ26/20 package (like the parity chips you need to complete the 4M modules), they are extremely likely to be standard 5V FPM 256K x 4 chips, commonly called 44256. Those were by far the most common memory chips used on entry-level 1MB SVGA cards around 1990-1994. The cross reference I posted should mention different vendor-specific chip type numbers for that kind of memory.

There are two "A413256J06" SOJ 26-pin chips soldered directly on the card's PCB paired with two socketed DIP-20 Samsung KM44C256AP-10 (256K x 4) for a total of 512 kB VRAM, so I think you're absolutely right about the chip's size, voltage and speed. I can add two more DIP-20 (in sockets) or SOJ26 chips soldered on the PCB.

This is the very same VGA card: https://www.vgamuseum.info/images/palcal/umc/ … 08af_top_hq.jpg (on this picture the socketed chips are missing)

There are memory configurations with six VRAM chips on the same videocard model: https://www.vgamuseum.info/index.php/cards/it … -umc-um85c408af

I'm afraid that the situation is likely more complicated, and you are unable to exceed 512KB on that type of card, although you are perfectly correct that there are cards with six chips shown at the VGA museum. Looking at https://www.vgamuseum.info/images/zaatharen/u … 5C408AF_fhq.jpg and https://www.vgamuseum.info/images/palcal/umc/ … d03a_top_hq.jpg with 4 chips, you will find chips labeled A414256J (I'm going to ignore the speed grade 07 or 06), while a card with 6 chips like https://www.vgamuseum.info/index.php/cards/it … -umc-um85c408af has A413256J chips on them.

My current speculation is that the 4 vs. 3 in the chip type actually represents 256K x 4 and 256K x 3! The A413256J chips I see at the VGA museum are likely partially broken chips where one of the four bits is not used. If that idea is correct, the 4-chip cards have two rows of two chips each, providing 2*4 = 8 bits per row. The 6-chip cards have two rows of three chips each, but each chip only contributes 3 bits, so 9 bits per row. The soldered jumpers MJP1-MJP6 can be used to select what RAM data pins are connected to what chip data pins. On the photo of the 6-chip cards, the data traces from the chip to the MJP solder bridges are completely at the top layer, so it's easy to see that each of the 8 jumpers connects to one pin on the chip. In the 6-chip configuration, the chip-connected solder positions are the top one of each individual jumper wire. In addition to the 8 solder positions connected to the UMC VGA chip, there are 8 used and 4 unused solder positions connecting to the RAM. The RAM-side connections of the jumper pins are on the bottom layer of the card.

So what this essentially means: Each row (of two or three chips) can physically provide 12 data bits (4 bits routed to each memory chip), 8 of those 12 bits are jumper-wired to the VGA chip and 4 of those 12 bits are ignored. If your card operates properly with just 2 chips per row, it means all 8 bits that are physically present actually work. So I am slightly surprised that your card has chips labelled A413256J instead of A414256J. Possibly the graphics card manufacturer tested the chips themself and found out that all 4 bits in this chip work well enough. As already all 8 bits per row are populated, there is no point in adding more RAM chips. So I expect that keeping to the current slogan in the topic "let's not make stupid things again", you don't try to upgrade that card.

Reply 30 of 32, by analog_programmer

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Thanks for the thoughts you've shared, mkarcher! I can't find any technical data for "A413256J" and "A414256J" chips to be sure what is the internal organization of these. And I don't want to spam with VGA off-topic in this thread. You're right about the slogan "let's not make stupid things again", so I'll ask if someone can provide working solution for increasing of VRAM of this card in the related section of the forum, but maybe tomorrow, 'couse right now I can't take some pictures of my UMC videocard.

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Reply 31 of 32, by pado

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analog_programmer wrote on 2024-04-06, 12:43:

There are memory configurations with six VRAM chips on the same videocard model: https://www.vgamuseum.info/index.php/cards/it … -umc-um85c408af

I don't know if you have noticed but there are pictures of two videocards with 6 memory chips on this page. Both have a uncommon combination:
- in the RAM 0-3 they have 1 A412256J + 2 A413256J (2+3+3 = 8 bits) = 8x256kb = 256kB
- in the RAM 4-6 they have 1 A412256J + 2 A413256J (2+3+3 = 8 bits) = 8x256kb = 256kB
for a total of 512kB VRAM.

I think that's the memory arrangement of this 6 VRAM chips videocard and, like mkarcher said, I don't know if you can increase the VRAM beyond 512kB.

Reply 32 of 32, by analog_programmer

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Theoretically four 512 K x 8 chips used as 512 K x 4 gives exactly 1 MB of RAM. I don't have an idea if this can be achieved on vidieocard's PCB with the given jumpers.

Let's move this VRAM discussion to: Video RAM chips for a UMC TK-85C408VGA ISA Video Card?

from СМ630 to Ryzen gen. 3
engineer's five pennies: this world goes south since everything's run by financiers and economists
this isn't voice chat, yet some people, overusing online communications, "talk" and "hear voices"