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Just got my original IBM compatible back! Need some help.....

fallemarg

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@GiGaBiTe - The cache chips I purchased make no mention of a TAG SRAM chip. How do I identify a TAG SRAM chip? I am guessing you are correct on the TAG chip being the issue. It's hard to see in the pictures of the monitor, but the upper left corner of the CRT screen is missing a piece. I have put everything back in the box and contacted the seller through e-bay while supplying the pictures for them to see. They Destroyed those foam bags that expand to fill a space from whatever drop they did to the monitor. So back to the questions. Where can I get a 32Kx8 TAG SRAM chip that is 15 or 20 ns?
 

GiGaBiTe

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TAG SRAMs are going to have a different P/N from regular SRAM chips. If you got chips that all had the same P/N then you don't have a TAG SRAM chip.

I'd love to get my hands on some TAG SRAMs myself, I've searched high and low for them everywhere and can't find any.
 

fallemarg

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What I cannot figure out is why they are so difficult to find. You would think that they would be everywhere, but I for the life of me cannot identify any in the places I normally look. Granted that is not a lot of places, but usually I can find something close to what I am looking for in those places. I going to call the PC recycle center tomorrow and see what I can find out.
 

GiGaBiTe

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They're so hard to find because unlike cache SRAMs where you have 4-16 of them on a board, there's only going to be 1-2 TAG SRAMs to accompany those chips. Most people that pull and sell those things probably don't even know what TAG SRAM is, which is why you never find it.

I'm going to hazard a guess when recyclers pull chips off of old motherboards, they look at the TAG chip(s) and don't make the connection that they're required for cache SRAMs to work and just discard them after pulling the SRAMs.

EDIT:

*gasp* I actually found some for sale:

http://www.ebay.com/itm/3-pieces-MK...309?pt=LH_DefaultDomain_0&hash=item419418d3dd

But damn is it expensive.
 
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fallemarg

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And it's not fast enough. Has to be 20ns or 15ns. That's what the motherboard information says. That was so close...

Edit - Doing a more concise search I found several which can be seen here - http://www.ebay.com/sch/i.html?_odk...ache+tag+RAM.TRS0&_nkw=Cache+tag+RAM&_sacat=0

But they are all 8kx8 or 16kx8, which won't work as I need 32kx8, which seems to be rarer than hens teeth or will they? I am only utilizing 128K of L2 cache. You would think since they are still manufacturing the 32kx8 SRAM chips for caching, that they would still have TAG Ram Chips, but I can't find anything on mouser or digikey.
 
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GiGaBiTe

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While SRAM is still in use today, there is little use for specialized TAG chips.

If you can't find the TAG chip, you can just use a normal SRAM and build the address comparator logic yourself. If you look at the data sheet for those TAG chips, it shows you a basic circuit diagram of how it works.

Just toss it all on a piece of perf board and wire a socket to it to install in the motherboard.
 

fallemarg

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I have been trying to talk with various people in regards to TAG chips and it has been said since I am only utilizing 128K of Cache, I can utilize a 8kx8 TAG Ram chip. Is that true? a couple bucks for a bunch of TAG Ram chips isn't going to bug me. Also any extras I will put back into the community here. Plus I do not have any circuit building experience. I can re-tin traces and solder/de-solder parts, but I have never built something all the way from the ground up , circuit board and all. I have wanted to. I need to make a three channel 3/32" input to one 3/32" output passive mixer, but I don't know where to start. I know I need put 10K Ohm resistors on each channel and that I need to create a ground plane, but that's about it.
 
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GiGaBiTe

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I can't imagine you'd need the same size chip for TAG since it's only storing cache entries and not actual cache data.

You can try a smaller TAG chip and see what happens. At worst, not all of the cache entries will fit and past some point you'll get slowdowns again.
 

fallemarg

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Okay. I ordered a set of 15ns TAG chips. It was cheaper to order a set of 10 than a set of 5 or 1. I guess I'll have extras if this works. And I confirmed with datasheets that the chips are indeed TAG chips. Here's hoping they aren't rebranded chips or anything.
 

fallemarg

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Okay, so I ordered the TAG chips like I stated earlier and everything seemed fine. Then I get an e-mail from the seller stating that they didn't have the part like they said, BUT they can order the part from another supplier for only 5 TIMES the price I paid! I told them no and said refund my money which they immediately refused to do. So two days later, a blocked paypal charge and a fraudulent business activity complaint lodged, I still don't have my money back and I won't get the parts. Never again. I swore I wouldn't purchase from China, and I should have stuck to that. That being said I found a company that lists that they still make 8kx8 TAG RAM chips, but I don't think they sell to the public. They have a reseller in the US, but there doesn't appear to be an easy way to contact the company to see if I can order the part. Aside from building a comparator logic circuit, does anyone else have any suggestions on how to move forward on my cache woes?
 

GiGaBiTe

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Disputes through paypal take time. When I had to deal with UPS destroying a shipment of mine, it took two weeks to get reimbursed.

That being said I found a company that lists that they still make 8kx8 TAG RAM chips, but I don't think they sell to the public.

Of course they'll sell to the public, you just have to make a minimum purchase order. It can be as little as a thousand or as high as a few hundred thousand.

Aside from building a comparator logic circuit, does anyone else have any suggestions on how to move forward on my cache woes?

Keep looking, you'll find something eventually.
 

fallemarg

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Of course they'll sell to the public, you just have to make a minimum purchase order. It can be as little as a thousand or as high as a few hundred thousand.

I wouldn't mind doing an order for more than I needed as long as other people were wanting them. I sent an e-mail to their distributor here in the US and I will wait to see what they say. It seems that they are sold usually in sets of 10, 50, 100, or 1000 from the places I could get information from. I will post more info when I know more. If I have to order 10 or 50, are there people out there that want these chips? Anything more than that is outside of my ability. I couldn't sit on 100 or 1000 chips.
 

fallemarg

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It has been a full week and the company never returned my contact in regards to purchasing memory chips from them. I guess they don't either carry the products any more or for some reason they did not receive my e-mail query. If someone has the time to do so, can someone post what their various cache speeds are on a 486DX2-66 with L2 Cache installed? I would very much appreciate it.
 

GiGaBiTe

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Do you mean like the system speed as a whole with cache vs without? Or do you mean like the timings of the chips (10, 15ns, etc.)

I benched a Socket 7 board with a 512KB COAST module a few years ago. A Pentium MMX 200 with 64M of RAM had a 10-15% performance increase in Quake depending on the resolution used.

Obviously a 486 system will be slower, but performance will be in some cases noticeably better with cache.
 

fallemarg

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Just a whole cache test would be fine. I don't mind the timings. I am just curious to see the MB/s transfer rates for the L1 and L2 so I can utilize them for comparison and see what kind of performance difference I am seeing without a dedicated TAG chip. Thanks for the response GiGaBiTe.
 

krebizfan

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Just a whole cache test would be fine. I don't mind the timings. I am just curious to see the MB/s transfer rates for the L1 and L2 so I can utilize them for comparison and see what kind of performance difference I am seeing without a dedicated TAG chip. Thanks for the response GiGaBiTe.

Vogons.org had a number of comparisons of 486s with and without cache. I can't locate the thread that was there right now but it might give you a fuller understanding of the possible performance benefits compared to workloads.

September 26, 1993 PC Magazine lists a number of 486 systems. The 486/66 systems with L2 cache cluster at slightly more than 10 MB per second while the cacheless 486/66 only did 7.197 MB per second. Sorry, review did not include a Packard Bell system so I have no idea how PB system would differ from either condition.
 

Anonymous Coward

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Are you sure this system requires a super special tag RAM? The vast majority of 486 systems I have seen used standard 8kx8 and 32kx8 SRAMs for the tag piece. The extra comparator logic mentioned should be built into the chipset (or sometimes using discrete logic). If you have a manual for your motherboard, it should tell you which parts are needed for the cache and tag RAMs.

*edit* I checked the TH99 docs for your board: http://museum.ttrk.ee/th99/m/P-R/31548.htm

TH99 isn't always 100% correct, but according to them you need a 32kx8 tag chip for 128kb cache. I would be quite surprised if a standard SRAM didn't work.
 

GiGaBiTe

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TH99 isn't always 100% correct, but according to them you need a 32kx8 tag chip for 128kb cache. I would be quite surprised if a standard SRAM didn't work.

Yes, you can use cache without TAG but it cripples performance. Sometimes performance is worse than without any cache installed.

Using a regular SRAM in a TAG socket won't work because the pinouts are different. At best, it won't work. At worst, something will burn.
 

fallemarg

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@Anonymous - I talked with several people and looked over the receipts from when I upgraded the machine when I was younger (My dad liked to keep all of that information and my step mother kept it after he passed. I have it now :)) and as other people said worked for them, I had an 8kx8 Cache TAG RAM chip back then. I only wish this machine hadn't been stripped before I got it back. It worked back then.

Also the motherboard has a slot specifically labeled TAG so it must run better with one. I think the 10MB/s someone else mentioned is off though, my ram is faster than that with the cache enabled. I know there are all sorts of variables that can affect the speed and timing, so I will be patient. I found the matched TAG chip info for my cache ram that I purchased and it is an 8kx8 chip. ATT7C174P-15. Looking around I haven't really been able to find any TAG chips specifically listed as 32Kx8. Since I have the datasheet for the ATT7C174P, maybe I can build that data comparator logic into a 28 pin dip socket, mount the 199P that I have then mount said socket and RAM into the TAG Socket. Do you guys think that might work?

I must say though, upgrading the HT216-32 to 1MB of RAM cleared up a vast majority of the weird pixel corruption issues. Now you just see the shimmer of corrupt pixels on the fades. Before you couldn't even touch Descent because the screen was awash in them, now at medium settings, it's pretty playable. I have 4 more of those ZIP chips that I haven't a use for currently. Anyone know any other systems that would use those NEC D424170V-70 ZIP chips?
 

Anonymous Coward

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I think I was misunderstood. The tag socket absolutely must be filled if you want to use the cache. I was just saying that the tag chip is normally not different from the regular SRAM chips that go in the other 4 sockets.
 
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