First post, by BitWrangler
- Rank
- l33t++
Howdy folks,
So bit of discussion going on in another thread about how flexible or not P4 systems are for speed control. I thought we could bring those insights in from there and add to them for a comprehensive "Everything you can do to get retro working well on P4". Reasons.. older stuff is getting ever more expensive, the P4 was the last intel class "in touch" with DOS/Win9x in general. Which implies yes there are specific examples of Core2 and later industrial machines with legacy features, but generally all that was left behind.
To get it all out of the way, K6 2/3 plus, Via C3, Mobile XP, Mobile Barton are all much superior solutions to highly adjustable retro systems, there are threads about them, this thread is about Pentium 4 class, including Celeron for the same sockets.
Still... Y tho' ? Because P4 prices are looking like making a move, this is maybe last chance for curbfind/free/$10 in local listings systems that might have a chance of being acceptable retro rigs . If you're reading this in a couple of years, I hope they're still among least expensive. Why do *I* care? Bending the boundaries, and I kinda have an urge to whittle everything down to "I can cope with it" rigs, while I can compare them to the genuine thing, before I divest myself of the hoard of real stuff.
Briefly, P4 class spanned socket 423, 478 and 775...
- 423 was first, Willamette core P4s, 400 FSB, SDRAM or RDRAM, AGP possibly 2x/4x, ISA slots common, slow... possibly too slow for golden era 486 with extreme kneecapping. Machines of this class may best be native late Windows 98 gamers, 98 drivers should exist for most contemporary hardware. Can dip a toe in early XP stuff, but run out of steam early. DOSbox capable, but might not manage fast 486/pentium speed.
- 478 next, Northwood and Prescott cores, 400/533/800 FSB some SDRAM, mostly DDR, AGP 4x/8x mainly, boards with ISA slots available.. may offer about the best DOS speed variability, given 3ghz plus 800Mhz FSB... should have a lot of win98 support, suitable as late/fast 98 gamer, early XP gamer, will run DOSbox nicely under windows, should run cycle accurate MAME cores for XTs, Tandys.
- 775 the final P4 platform, Northwood, Prescot, Cedar Mill cores extending to Core2 Conroe and up 533/800(/1066/1333/1600) FSBs (Not P4 official) DDR and DDR2, AGP 4/8x and PCIe 8x or 16x for graphics, ISA slots hard to find, some late boards may not have 32 bit PCI... some win98 support but coverage getting patchy, could be a late/fast 98 gamer, slightly longer spell of early XP gaming for faster cores... probably only 2 low DOS speeds. Will run DOSbox nicely under windows, should run cycle accurate MAME cores for XTs, Tandys.
But that needs fleshing out. Following are the postings that inspired the thread, however, input is sought on all aspects, other slowdown utils and methods, which onboard/PCI audio chipsets have DOS functionality, which GPUs in AGP and PCIe, links to relevant threads good.
pixel_workbench wrote on 2022-01-20, 04:31:This is not completely accurate. The reason it appears so is because using "SETMUL L1D" on a P4 actually disables the L2 cache, […]
bloodem wrote on 2022-01-15, 10:31:P4 is terrible when it comes to speed flexibility. There's no way of reaching 386 / 486 speeds, because even when disabling the L1 cache, the Netburst architecture is still too fast.
This is not completely accurate. The reason it appears so is because using "SETMUL L1D" on a P4 actually disables the L2 cache, and not the L1. I tested this on a board that can disable caches in BIOS, and then the P4 slows down to a level of a slow 486. Looking at the memory test graph in Speedsys supports this theory. Below are some DOS benches from my testing.
P4 2.8 Northwood 400MHz FSB, Soyo P4I845PE, 512MB DDR-266, Radeon 9550
Normal:
3dbench1.0c = 460.6
PCPbench = 406.1
Doom fps = 121.45
Using SETMUL L1D:
3dbench1.0c = 333.5
PCPbench = 132.1
Doom fps = 84.78
L1 & L2 caches disabled in BIOS:
3dbench1.0c = 21.5
PCPbench = 6.6
Doom fps = 10.36
bloodem wrote on 2022-01-20, 06:48:Awesome find, pixel_workbench! True, I was disabling the L1 cache with setmul, because none of the socket 478 boards that I test […]
pixel_workbench wrote on 2022-01-20, 04:31:This is not completely accurate. The reason it appears so is because using "SETMUL L1D" on a P4 actually disables the L2 cache, and not the L1. I tested this on a board that can disable caches in BIOS, and then the P4 slows down to a level of a slow 486. Looking at the memory test graph in Speedsys supports this theory. Below are some DOS benches from my testing.
Awesome find, pixel_workbench!
True, I was disabling the L1 cache with setmul, because none of the socket 478 boards that I tested had the BIOS option to do so.
Anyway, although that slow 486 speed is actually very nice for me (I've found that most/all of my favorite early DOS games work just fine at this speed), this doesn't really change the fact that, overall, P4 platforms are still far from being flexible.
BitWrangler wrote on 2022-01-20, 13:13:Hmmm wonder what it's like with an 800 Mhz FSB P4 when you do L1 off, Pentium class? then maybe L1 off at 533 is 486 and at 400 is nearer 386 (bearing in mind multi lower on 800 chip, so at 400 it's at early willamette clock speeds, but IPC might be higher)
Though I guess I could scare up the P4M 1.8 I thought I had kicking round somewhere, and see how speedstep behaves.
Edit: reviewing my options of hardware to play around with this on, and I don't seem to have a "goldilocks" CPU or motherboard combo, stuff that's either too good or too bad. Too good mainly meaning I've got different plans for it already. In investigating whether a 331 Celerunt would take 200/800Mhz I found that there's an additional FSB step that might be available on some socket 775 boards. Intel specced a 166/667 FSB which they never released a desktop CPU for, but only used on mobile. However, it might have been implemented with correct PCI/AGP dividers in some boards/chipsets, because MFers never knew Intel wouldn't release 166/667 desktop CPUs. Taping over a pad is meant to enable it. Useful to make settings more granular, modular, interactive-odular. Or because it's a huge leap between 533 and 800 if you've got 533 CPUs. 533 to 800 is possible but you need a low multi (slow) 533 CPU that's practically perfect.
edit: formatting improvement
edit2: Getting a mention up here because being based on the same designs certain Xeons are arguably "Pentium 4 class hardware" and have a bonus, Xeons of this era are downward unlocked, you can set lower multipliers. So don't necessarily turn down a free/cheap Xeon, but don't necessarily lumber yourself with it either, check out expansion options, you might not want to deal with only one or two "normal" PCI slots and no AGP etc, you might not want to buy funky RAM cards or weird hard drives. Server class hardware is more likely to head into the weeds in those areas, workstation class might be more flexible (and less likely to be housed in something approximating a borg cube, or a large slice thereof.) ... a primer from the era on P4 Xeon possibilities... https://www.overclockers.com/forums/threads/t … -thread.329096/
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