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5160 w/ NEC V20 Questions

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Raven

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1. Can I do this? I assume it's safe, but just in case...

2. What's the deal with coprocessors and the V20 - does the V20 have a special coprocessor? Will it only run at 8mhz in the 5160 and thus be fine with the 8087? Does it have a built-in coprocessor?

3. Will it give my 5160 the tiny kick in the pants it needs to play DIGGER and Monuments of Mars at full speed? They both run at a playable pace, but a bit quicker wouldn't hurt.
 
1. It should work fine, though some have reported that reset sometimes needs work to get it to come up at BRS time.
2. The 8087 will work, though NEC did make its own version, but it's very very hard to find.

Most anecdotal reports say you get about 20% on CPU-bound applications. It's hard to quantify exactly because the V20 has a different internal architecture. The big advantage is that the V20 implements the non-privileged 80286 instructions.
 
Excuse my ignorance, but could you please explain the first one.. "reset sometimes needs work to get it to come up at BRS time"?
 
Is there a DOS utility that can identify the Math Co-Processor? I have a V20 in my 5160 and I am wondering which co-processor I have (if any) and I am too lazy to pop it open to find out.

Chuck(G) said:
1. It should work fine, though some have reported that reset sometimes needs work to get it to come up at BRS time.
Click to expand...

I'd be curious to know what you mean by this as well.

Chuck(G) said:
The big advantage is that the V20 implements the non-privileged 80286 instructions.
Click to expand...

That means you can run some software on it that actually requires a 286, assuming they don't call for an privileged instructions? And by privileged do you mean protected mode?
 
I've seen one or two 5150/5160s where the Power Good reset comes up a bit too fast after the power actually reaches +5. It's not a big thing, but it happens to some machines. The good news is that it's consistent--if it doesn't work, it never works. Usually this means changing a capacitor in the power supply.
 
My 5160 has a V20 and standard 8087 copro, as far as I experience it it works fine.
Benchmarks at up to + 20% -depending on which you use...
 
Raven said:
Will it only run at 8mhz in the 5160 and thus be fine with the 8087?
Click to expand...
When you pull out the 8088 and put in a V20, the CPU socket will still be fed the same clock signal, nothing faster. The performance increase comes from the fact that the V20 is more efficient at executing instructions.

The 8087 will still be fed the same clock signal.


I had a problem in my early 5160 where after replacing the 8088 with a V20, the machine would no longer start (just like a dead motherboard). If I removed the AST SixPakPlus card, the machine would then start. I discovered that if I updated the first revision BIOS to the third revision one, all worked - I could have both the V20 and the SixPakPlus fitted.
 
Mine has a sticker on one side on the back that says 089-26 5160-4029293. What I'm hoping is that that will tell us what model this is - it's a 256-640K model fitted with 640k. Anywho, how can I figure out which BIOS revision I've got (so I can figure out why I'm having the problem modem7 describes if I run across it)?

I realize it'll be fed the same clock signal, but I also realize that an NEC V20 is rated for up to 16mhz, and that later CPUs can have an internal multiplier on the clock signal. I had no idea when that technology might have cropped up, so it could have had a 1.5 or 2x multiplier for all I knew.

I've seen people saying that the V20 gives you a subset of 286 instructions, but Wikipedia says it gives you a complete set of 186 instructions. This could mean the same thing, but why refer to it as a subset of the 286 - due to the 186's limited use and popularity?
 
Jorg said:
Multipliers came in with the later 80486s (e.g. DX/2, DX/3)
Click to expand...

I've been living in 486 land a long time. Prior to this, I've only had portable 808x systems with no real need for a CPU upgrade or anything. I have no functional 286 machine(s), and don't use the few 386 machines I have, because 486s can do everything that they can (at least that I've found to do, I know a few games need a 386 specifically).

Anywho when the Epson Equity I+ gets here I will test the games on it (it has a V20) and figure out what I'm doing from there.
 
lutiana said:
Check out this thread. It should help you identify the BIOS revision.
Click to expand...

I read that thread, it helped me tell what the differences between revisions are, but not how to tell. Unless the only way to tell is to look up datasheets to check the size of chips at various locations, that is, but it sounds like there should be an easier way - perhaps a software tool.
 
Nice - much easier than opening it up and trying to read the chips without dismounting various parts and cables.

It printed 01/10/86||-.. I assume that the last two characters weren't important. :p

That means that I don't have the "first revision BIOS" that has the problem with memory expansion cards and a V20.

I noticed that the final revision after mine states:
"* Contained some fixes for minor keyboard bugs related mainly to the enhanced keyboard."

If I intend to put an Enhanced Keyboard (the one from the XT-286) on this machine, is it worth backing up and then flashing the EPROM? It doesn't give much detail as to what bugs were fixed. Can these be flashed, for that matter, or do I need to buy a second, flashable, chip if I decide I need to flash it?

As well, I realized I was being an idiot through the first half of this thread and was assuming that all 8088s ran at 8mhz, forgetting that they run at 4.77mhz and only turbo ones clock up to 8mhz when using the turbo mode. Anywho, has anybody ever added a turbo function to an IBM 5160 before? If so, is there documentation I could look at? I realize that the BIOS might get wonky with it's assumptions about NOP length at 4.77mhz, so I'd have to use a third party BIOS such as this one (http://www.phatcode.net/downloads.php?id=101).

I think it would be pretty cool to have an NEC V20 @ 10mhz turbo in a 5160 - lol. One step short of cheating by adding an accelerator.

Thoughts?
 
First of all, you'd need to swap all of the peripheral chips (8254, 8237, 8255 to their 8MHz (or 10MHz) versions). Then, you've got the issue of having to run the 8254 CTC at the right rate, otherwise program timing and clock updating will be off.

Short story--if you want a faster machine, install an accelerator card or get faster motherboard. It's not worth trying to retrofit a 4.77MHz board.
 
Aye I wouldn't go that far (mangling a perfectly good machine in the process) - that's nuts. I'm scouting around for an accelerator board at the moment, and the V20 should give it enough of a kick to run the few games that it lags just slightly on. Otherwise it'll all bug me less when my MediaGX gets here and I get to playing with that, since it'll run 286->Pentium (limited on the Pentium end, of course) titles just fine. I love pushing hardware far beyond it's original limits, however, and thus I explore all kinds of options. If the V20 doesn't do much for the 5160 then I'll leave it in the Equity and just play the more demanding games on it or the MediaGX.

I doubt this, but is there any functional or speed difference between AMD and Intel 8088 chips? The 5160 has an AMD part in it but I happen to have an Intel 8088 in a case here (same case the 8087 I've installed came from) that I could swap if there's any point.

Thanks for all of the info, btw - these machines are from years before I was born, so my knowledge of them has many gaps.
 
Raven said:
I doubt this, but is there any functional or speed difference between AMD and Intel 8088 chips? The 5160 has an AMD part in it but I happen to have an Intel 8088 in a case here (same case the 8087 I've installed came from) that I could swap if there's any point.
Click to expand...

AMD was an Intel-licensed second-source manufacturer of the 8088 and 8086, so you're getting the same exact thing as the Intel, just with a different logo on top. IBM required at least two suppliers for all the chips they used, so Intel was their main supplier for the 8088, and AMD was the backup. Eventually IBM began using 8088s made by NEC as well (not to be confused with the V20; these were just standard 8088 chips made by NEC).
 
Raven said:
It printed 01/10/86||-.. I assume that the last two characters weren't important. :p
That means that I don't have the "first revision BIOS" that has the problem with memory expansion cards and a V20.
Click to expand...
Maybe just certain cards, not all "memory expansion cards".

I went from 11/08/82 to 05/09/86, bypassing 01/10/86. So maybe 01/10/86 also has the problem, but it seems unlikely - the description of 01/10/86 reads like a lot of minor changes (not detailed) were made.

Raven said:
If I intend to put an Enhanced Keyboard (the one from the XT-286) on this machine,
Click to expand...
The XT-286 is an AT class machine and therefore the keyboard (also AT class) won't work on a 5160, unless the keyboard is an auto-switching type.

Raven said:
Can these be flashed, for that matter
Click to expand...
No, the supplied ROMs can't be flashed.

Raven said:
or do I need to buy a second, flashable, chip if I decide I need to flash it?
Click to expand...
I've never gone down that road. Maybe someone else can comment on feasibility/issues.
 
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