Shouldn't mem transfers for Mediators (orother brands) for A4000 be faster the equivalent A1200's??

[Jose]

Ok, I've read somewhere that the transfer speed is faster on the A4000/3000 versions of the PCI busboards cause the CPU connector is faster on the A4000 than the A1200's.
There was even this site, (now down) that clearly stated the Gfx boards were faster with the A4000's situation.
But recently, bout two months or so there were some tests (made by Karlos I think) run by people that proved there is not a big difference?
Can someone clarify this, as I was having a hell lot a work and didn't read it, and can't  find the actual thread now?
 

[Karlos]

Hi,

The information I got back indicated that CPU driven transfers from fast ram to the gfx memory were not especially faster in the Mediator4000 than the Mediator1200.

The test program in question copied data to the gfx card using a loop 16x unrolled 32-bit copy loop on cache aligned source data (16-byte) so in theory should have be best case copy.

My miggy is down just now so I'm fishing out info from the replies I got in my email

As a rough guide (all tests at 1024x768 16-bit)

My machine:

A1200T
BlizzPPC with 040@25MHz
64Mb 60ns EDO ram
BVision / CGX4.2
result : 8874 K/s

Now, having fished through them I found a typical (comparable) 4000/1200 mediator pair (same gfx card, same rtg, same mem speed)

Mediator systems (both using 060 + voodoo 3 3000)

Amiga 4000 (Mediator 4000)
Cyberstorm MkIII 68060@50Mhz
80Mb Cyberstorm RAM (60ns)
8Mb motherboard fastram
Voodoo 3 3000, Avenger, 16Mb / Picasso96 v2.1
result : 7947 K/s

A1200T (Mediator 1200)
Blizz 060@66MHz
128Mb 60ns EDO ram
Voodoo 3 3000 16Mb / Picasso96 v2.1
result : 8290 K/s

Ok, the 1200 system is 16MHz faster CPU but the results are similar for all three systems.

I guess there are many factors but the results I got were pretty consistent with those above.

Probably the A4K at 66MHz would win here : looking at the figures - a crude estimate based on the 16Mhz increase clockspeed would be in the order of 10.5 M/s.

What I discovered is that the G-Rex systems had considerably faster bus speed results, averaging 20M/s. One system (A4k 060@66 IIRC) managed close to 40M/s in that test...

[lempkee]

well there is quite a diff on some areas..

ie if u are on ppc..

the a1200's suffer from the 8mb windows, which means u cant have more than 8mb rtg ram what so ever atm...(wos bug?)

so basically if u have a voodoo5 on an a4k and ppc it will then do a overkill compared to the a1200ppc with voodoo5...

the grexx is alot faster imho than the mediator on a1200.

hope it helps...

[Karlos]

8Mb limit for A1200? Never heard of that one before :-) Mind you I might not have paid attention.

True or not, I'd assume the amount of accessible gfx memory would have no meaningful impact on the transfer speed - thats purely down to the bus.

Also note, in relation to my tests,  we are talking how quickly we can copy data from fast ram into the gfx card's memory, using the CPU to do the copy.

There was no indication in the results that I got from the volunteers (cheers folks) that the Mediator4000 was much faster than the Mediator1200 in this respect.

As for the G-Rex, I agree. It outpaced the mediator in this area consistently.

As for actual graphics peformance overall, the impact of all of this is relatively minor.

For 2D and 3D alike most operations happen locally on the card. The only time the bus speed comes into it is when data has to be written to the card (texture map uploading or geometry data) or retrieved from it (reading back pixels etc).

[tjaoz]

@Karlos

What I discovered is that the G-Rex systems had considerably faster bus speed results, averaging 20M/s. One system (A4k 060@66 IIRC) managed close to 40M/s in that test...

 Grex 1200 and Grex 4000 use the same PCI bridge logic as BVision.  The effect is that the Grex bustest results are always the same as for the BVison card.

Grex bustest results depend on the BlizzardPPC/Cyberstorm card  version. 40MB/s is a rumor only

[Karlos]

Rumour or not, one lucky G-Rex 4000 owner managed it - he got about 30M/s for that test.

-edit-

Aha - found it. He got 33 M/s copy and 39M/s set (which is basically CPU register -> memory rather than memory -> memory)

-end edit-

He had :

CSPPC with 060 @ 66MHz, GRex 4000 and a Voodoo 3 (IIRC)

For the record, most of the G-Rex results I got back were typically 13-15 M/s. That's faster than the Mediator.

However, unless you own a BPPC/CSPPC, the G-Rex not an option.

Jose's original question was about Mediator1200 v Mediator4000 - I didn't observe a signifigant difference in performance between the two.

[tjaoz]

@Karlos

Rumour or not, one lucky G-Rex 4000 owner managed it - he got about 30M/s for that test.

Einmal ist keinmal

For the record, most of the G-Rex results I got back were typically 13-15 M/s. That's faster than the Mediator.

Mediator 1200 bustest is from 8 to 18MB/s. It depends on the turbo card.

[Karlos]

tjaoz wrote:
Mediator 1200 bustest is from 8 to 18MB/s. It depends on the turbo card.

I'm not saying youre wrong - I'm sure that what you say is correct. However, were talking specifically about gfx cards operating under PCI here, not just the pure bus speed, but how fast can we shove data to the card

IIRC, Jose was thinking about some sort of movie player code and copy bandwidth issues a while ago - I'm guessing his original question here may be something to do with that.

Quite a lot of brave folks ran my test programs and for a wide spread of Mediator based systems I found that the speed of CPU access to  video ram on a PCI gfx card (usually voodoo) was not very different accross the range 040@25 to 060 @ 66 for both the Mediator1200 and 4000 versions.

The slowest was about 6.5M/s, the fastest was about 10M/s.

I don't know about BusTest, but the copy code I used was my own asm routines that are typically faster than CopyMemQuick(), using 16x unrolled 32-bit, aligned transfers.

[lempkee]

i tried running a game as a comparisment but sadly that wont do for much (since 603 vs 604)
but i can say for sure that its way faster on a4k (mediators)

anyway u see my system i get 7.2 megs a sec in transfers and the 604 with 060 got past 16megs.

i see that as a rellevance...

anyway..about the damn memory window...its a pain in the arse if you want rtg mem, as rtg mem speeds up your games/demos etc....
i hope this bug gets fixed asap!

not too sure if the grexx has this bug, but i guess it does as i belived someone said it was a wos bug!

sorry for bouncing off track, just wanted to clear up what i said earlier.

[Piru]

the a1200's suffer from the 8mb windows, which means u cant have more than 8mb rtg ram what so ever atm...(wos bug?)

Even though WOS is famous for its' bugs, this one is not software. The 8mb limit is in Mediator hardware. No software can fix this.

[Jose]

Hey all.
I was only concerned about the speed that you can writte data to the Gfx memory. I thougth about getting a Gfx card cause AGA is too slow.
but since I don't have A4000 I'd get a Mediator for my A1200 and a PCI Gfx card. Then I remembered  reading somewhere that the mem. transfers are only 10mb/s or someting wich is really slow and doesnt justify the price...Even AGA has transfers close to that.
I guess later with a PPC processor in the Mediator it's gonna be different.

[CaptainFrank]

Hi,

> Even though WOS is famous for its' bugs, this one is not software. The 8mb limit is in Mediator hardware. No software can fix this.

It`s not really a Mediator Limit.  The A1200`s trapdoor expansion only has 24 Address lines (24bit)  which gives 16mb of available addresses.  8mb are allocated by ROM, Custom Chips and Chip RAM etc....  The other 8mb are free to use, but PCMCIA exists in the last 4mb of this ram.  Thats why, when you use the Mediator in 8Mb mode, you lose PCMCIA.

The Mediator is limited by the A1200 itself, not by any sort of Mediator bug/Limit.  Elbox`s driver is capable of shifting the 4/8mb "window" around, giving them full access to the graphics cards memory.  I don`t believe that the information to do this is freely available though.

AFAIK, the A4000 version doesn`t suffer the 8mb Limit.

Best Regards,


Frank.

[Piru]

It`s not really a Mediator Limit. The A1200`s trapdoor expansion only has 24 Address lines (24bit) which gives 16mb of available addresses

Indeed. But mediator doesn't really work around this limit, so I consider the Mediator flawed in a sense.

GRex (that connects directly to BPPC pci-like bus) has no such limit.

[Karlos]

@Jose

I realise all this might have put you off so I'll give you a better perspective :-)

Dont let the bandwidth issue desuade you. The AGA bandwidth (max 7M/s) drops dramatically with the depth/size of the screen. With my BVision I still get 8-10M/s even at 1600x1200 @ 75Hz - I imagine PCI cards on the mediator have the same performance.

Just to reiterate about graphics performance :

Karlos wrote:

As for actual graphics peformance overall, the impact of all of this is relatively minor.

For 2D and 3D alike most operations happen locally on the card. The only time the bus speed comes into it is when data has to be written to the card (texture map uploading or geometry data) or retrieved from it (reading back pixels etc).

In short a good graphics card slaughters AGA in basic performance - even if the raw bus speed doesnt look many times higher.

Refresh rates, colour depth, blitting, rasterizing are all accelerated far beyond AGAs abilities.

[Gaidheal]

Ditto about performance.

The whole point of graphics accelerators is exactly that.  After all, if it was just throughput, we'd all use our fast CPUs and DDR400 RAM :¬) (or better yet, RAMBUS..)

John